{"id":100283,"date":"2026-02-15T20:31:45","date_gmt":"2026-02-15T20:31:45","guid":{"rendered":"https:\/\/vibromera.eu\/?post_type=calculator&#038;p=100283"},"modified":"2026-07-16T23:00:07","modified_gmt":"2026-07-16T23:00:07","slug":"vibration-glossary","status":"publish","type":"calculator","link":"https:\/\/vibromera.eu\/el\/calculators\/vibration-glossary\/","title":{"rendered":"Source-Controlled Vibration Reference Glossary"},"content":{"rendered":"\n<script type=\"application\/ld+json\">{\"@context\":\"https:\/\/schema.org\",\"@type\":\"DefinedTermSet\",\"name\":\"Source-Controlled Vibration Reference Glossary\",\"description\":\"87 reviewed vibration terms with explicit formula scope, source status and non-diagnostic cautions.\",\"url\":\"https:\/\/vibromera.eu\/calculators\/vibration-glossary\/\",\"inLanguage\":\"en\",\"hasDefinedTerm\":[{\"@type\":\"DefinedTerm\",\"name\":\"Acceleration\",\"description\":\"The time derivative of velocity and the second time derivative of displacement when all quantities use the same coordinate and reference frame.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Alignment\",\"description\":\"The geometric state of machine axes or components relative to specified position and angular tolerances.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Amplitude\",\"description\":\"A magnitude used to describe a signal or motion. The quantity, amplitude descriptor, reference, frequency band and processing must be stated.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Antifriction Bearing\",\"description\":\"An older or informal label for a rolling-element bearing, such as a ball or roller bearing, contrasted with a plain or fluid-film bearing.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Axial\",\"description\":\"A direction parallel to a defined shaft or machine axis.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Balancing\",\"description\":\"A process for assessing and, when required, correcting rotor mass distribution so that residual unbalance meets an applicable specification.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Bandwidth\",\"description\":\"The interval between stated lower and upper frequency limits of a measurement, filter or analysis process.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Baseline\",\"description\":\"A documented reference measurement or state used for later comparison under sufficiently comparable operating and measurement conditions.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Bearing Defect Frequency\",\"description\":\"A commonly used label for a theoretical rolling-bearing kinematic frequency associated with a race, rolling element or cage.\"},{\"@type\":\"DefinedTerm\",\"name\":\"BPFI\",\"description\":\"For a stationary outer ring and the stated pure-rolling geometry, the theoretical rate at which rolling elements pass a point on the inner race.\"},{\"@type\":\"DefinedTerm\",\"name\":\"BPFO\",\"description\":\"For a stationary outer ring and the stated pure-rolling geometry, the theoretical rate at which rolling elements pass a point on the outer race.\"},{\"@type\":\"DefinedTerm\",\"name\":\"BSF\",\"description\":\"For the stated rolling-bearing geometry, the theoretical spin frequency of a rolling element about its own axis.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Broadband\",\"description\":\"Signal content distributed over a stated frequency interval rather than represented only by isolated narrow components.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Campbell Diagram\",\"description\":\"A plot of measured or calculated frequency against rotational speed, often including order lines, modal branches or response amplitude.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Cavitation\",\"description\":\"Formation and collapse or transport of vapour cavities when local liquid pressure falls sufficiently low relative to vapour pressure.\"},{\"@type\":\"DefinedTerm\",\"name\":\"CPM\",\"description\":\"A frequency expression counting cycles per minute.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Crest Factor\",\"description\":\"For a stated record and preprocessing, the maximum absolute magnitude divided by the RMS magnitude.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Critical Speed\",\"description\":\"A rotational speed at which a rotor-system response associated with a mode can become resonant under a particular excitation order and operating condition.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Damping\",\"description\":\"Mechanisms that dissipate or redistribute vibration energy and influence response amplitude, phase and decay.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Displacement\",\"description\":\"Change of position relative to a stated reference. In machinery work it can be absolute motion, relative shaft-to-bearing motion, or one coordinate of an orbit.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Eccentricity\",\"description\":\"Separation between specified geometric, rotation or mass-centre axes or centres.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Envelope Analysis\",\"description\":\"Demodulation of amplitude variation from a selected carrier band, often after band-pass filtering and rectification or analytic-signal processing.\"},{\"@type\":\"DefinedTerm\",\"name\":\"FFT\",\"description\":\"A family of algorithms that efficiently computes a discrete Fourier transform.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Frequency\",\"description\":\"Rate of repetition of a periodic phenomenon, expressed in hertz when measured in cycles per second.\"},{\"@type\":\"DefinedTerm\",\"name\":\"FTF\",\"description\":\"For the stated bearing model, the theoretical rotational frequency of the cage or rolling-element train.\"},{\"@type\":\"DefinedTerm\",\"name\":\"g-value\",\"description\":\"An acceleration magnitude expressed as a ratio to the conventional standard acceleration g\u2099.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Harmonic\",\"description\":\"A component whose frequency is an integer multiple of a stated fundamental frequency.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Hz\",\"description\":\"The SI derived unit for frequency, equal to reciprocal seconds.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Imbalance\",\"description\":\"A common informal synonym for unbalance. ISO rotor-balancing work uses the term \u201cunbalance\u201d; exact normative wording requires the licensed vocabulary.\"},{\"@type\":\"DefinedTerm\",\"name\":\"ISO 10816\",\"description\":\"A legacy multi-part family for evaluating machine vibration measured on non-rotating parts. Parts have different life-cycle states and many have corresponding ISO 20816 replacements.\"},{\"@type\":\"DefinedTerm\",\"name\":\"ISO 20816\",\"description\":\"A multi-part family titled \u201cMeasurement and evaluation of machine vibration\u201d. ISO 20816-1:2016 is the published general-guidelines edition and is marked for revision.\"},{\"@type\":\"DefinedTerm\",\"name\":\"ISO 21940\",\"description\":\"The rotor-balancing series. ISO 21940-1:2019 is the current introduction; ISO 21940-11:2016 plus Amendment 1:2022 addresses procedures and tolerances for rotors with rigid behaviour.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Jerk\",\"description\":\"Time derivative of acceleration and third time derivative of displacement when the derivatives share one coordinate and reference.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Journal Bearing\",\"description\":\"A plain bearing in which a journal is supported by a sliding interface,commonly with a lubricating film.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Kurtosis\",\"description\":\"A normalized fourth central moment of a distribution or sampled record. Pearson kurtosis for an ideal Gaussian distribution is 3; excess kurtosis is Pearson kurtosis minus 3.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Logarithmic Decrement\",\"description\":\"Natural logarithm of the ratio of same-direction amplitudes separated by one or more cycles in a decaying response.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Looseness\",\"description\":\"Loss or variation of an intended mechanical constraint,fit,preload or support condition.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Misalignment\",\"description\":\"A geometric condition in which intended coupled or supported axes do not meet the applicable offset,angular or positional requirement.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Natural Frequency\",\"description\":\"A modal frequency of free vibration for a specified system and boundary condition.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Octave\",\"description\":\"A frequency ratio of 2:1. Fractional-octave bands require stated centre-frequency and band-edge conventions.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Oil Whirl\",\"description\":\"A fluid-induced subsynchronous precessional response associated with a fluid-film bearing system.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Oil Whip\",\"description\":\"A fluid-induced rotor instability in which a subsynchronous response can become associated with a rotor mode over a speed range.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Orbit\",\"description\":\"The locus of shaft or rotor position in a transverse plane,constructed from two simultaneous displacement channels and their geometry.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Orders\",\"description\":\"Frequency normalized by a rotational reference. Order k means f = k f\u1d63 at that operating instant.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Overall Level\",\"description\":\"An aggregate signal magnitude over a stated measurement chain and frequency band.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Peak\",\"description\":\"A stated extreme of a record:positive peak,negative peak or maximum absolute peak must be distinguished.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Peak-to-Peak\",\"description\":\"Difference between the maximum and minimum values in a stated record.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Phase\",\"description\":\"Angular or time relationship between components at a stated frequency and a stated reference.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Proximity Probe\",\"description\":\"A non-contact displacement transducer system,often eddy-current,used to measure probe-to-target gap and dynamic relative motion.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Radial\",\"description\":\"A direction perpendicular to a defined shaft or rotation axis.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Resonance\",\"description\":\"A condition in which forcing near a modal frequency produces a response strongly influenced by that mode.\"},{\"@type\":\"DefinedTerm\",\"name\":\"RMS\",\"description\":\"Square root of the mean of squared values over a stated record or interval.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Rotor\",\"description\":\"The rotating assembly or component considered in a machine model or balancing procedure.\"},{\"@type\":\"DefinedTerm\",\"name\":\"RPM\",\"description\":\"Rotational rate expressed as revolutions per minute.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Runout\",\"description\":\"Apparent variation associated with target geometry,shaft motion,target electrical properties or the measurement system as the shaft turns.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Shaft\",\"description\":\"A rotating member used to transmit torque or support rotating components.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Sideband\",\"description\":\"A component adjacent to a carrier or principal component,with spacing associated with modulation or another periodic process.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Spectrum\",\"description\":\"A representation of signal magnitude,phase or power-related quantity versus frequency.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Subharmonic\",\"description\":\"A component at a rational fraction of a stated fundamental or reference frequency.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Synchronous\",\"description\":\"Phase-coherent with a stated rotational reference. Some practices use \u201csynchronous\u201d for integer orders; others reserve it for 1\u00d7,so the convention must be stated.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Time Waveform\",\"description\":\"Recorded signal value versus time.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Transmissibility\",\"description\":\"A ratio of response to input under a precisely defined excitation and output convention.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Trend\",\"description\":\"A time-ordered series of comparable measurements used to examine change.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Unbalance\",\"description\":\"A rotor mass-distribution condition for which the principal inertia axis does not coincide with the rotation axis as required by the model.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Velocity\",\"description\":\"Time derivative of displacement in the same coordinate and reference frame.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Vibration\",\"description\":\"Variation of a mechanical quantity about a reference value,commonly described using displacement,velocity or acceleration versus time or frequency.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Vibration Severity\",\"description\":\"An evaluation outcome obtained by applying stated criteria to a defined machine,measurement quantity,location,direction,band and operating condition.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Waterfall Plot\",\"description\":\"A sequence of spectra displayed against time,speed or another ordering variable.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Wavelength\",\"description\":\"Spatial period of a propagating wave.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Whirl\",\"description\":\"Precessional or orbital motion of a rotor or shaft centre. Forward and backward directions are defined relative to shaft rotation and the coordinate convention.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Window Function\",\"description\":\"A weighting applied to a finite record before a transform to control spectral-leakage behaviour.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Zero-to-Peak\",\"description\":\"Excursion from a stated zero or mean reference to one stated extreme.\"},{\"@type\":\"DefinedTerm\",\"name\":\"1\u00d7 (First Order)\",\"description\":\"A component whose frequency equals the instantaneous rotational reference frequency.\"},{\"@type\":\"DefinedTerm\",\"name\":\"2\u00d7 (Second Order)\",\"description\":\"A component whose frequency is twice the instantaneous rotational reference frequency.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Accelerometer\",\"description\":\"A transducer system whose primary measurand is acceleration.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Condition Monitoring\",\"description\":\"Acquisition and interpretation of information about an item or machine over time for assessment of condition and change.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Coupling\",\"description\":\"A mechanical element or assembly connecting shafts to transmit torque while providing the designed accommodation or constraint.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Demodulation\",\"description\":\"Signal processing that estimates information carried by modulation of another signal.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Gear Mesh Frequency\",\"description\":\"For a gear with Z teeth rotating at f\u1d63, the ideal tooth-engagement repetition frequency.\"},{\"@type\":\"DefinedTerm\",\"name\":\"High-Frequency Detection\",\"description\":\"A vendor- or procedure-specific label for measuring or processing a selected high-frequency band.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Impact Test\",\"description\":\"A dynamic test using a measured impact input and measured response to estimate frequency-response or modal information.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Keyphasor\",\"description\":\"A once-per-revolution or otherwise defined shaft-reference signal used for speed,phase or order tracking.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Modal Analysis\",\"description\":\"Identification or calculation of modal properties such as natural frequencies,damping and mode shapes for a stated system and boundary condition.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Orbit Plot\",\"description\":\"A display of one transverse displacement channel against another to show a shaft or rotor locus.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Vane Pass Frequency\",\"description\":\"For Z equally spaced vanes rotating at f\u1d63 past a fixed reference,the ideal passage frequency.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Blade Pass Frequency\",\"description\":\"For Z equally spaced blades rotating at f\u1d63 past a fixed reference,the ideal passage frequency.\"},{\"@type\":\"DefinedTerm\",\"name\":\"Torsional Vibration\",\"description\":\"Oscillatory variation of angular position,angular velocity or torque about a shaft axis.\"}]}<\/script>\n<script type=\"application\/ld+json\">{\"@context\":\"https:\/\/schema.org\",\"@type\":\"BreadcrumbList\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\/\/vibromera.eu\/\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"Calculators\",\"item\":\"https:\/\/vibromera.eu\/calculators\/\"},{\"@type\":\"ListItem\",\"position\":3,\"name\":\"Vibration Reference Glossary\",\"item\":\"https:\/\/vibromera.eu\/calculators\/vibration-glossary\/\"}]}<\/script>\n<style>\n#vbm-vref{--ink:#17242b;--muted:#566a74;--line:#d8e1e5;--soft:#f5f8f9;--accent:#146b78;--warm:#fff7e8;max-width:1120px;margin:0 auto;padding:18px 16px 42px;color:var(--ink);font:15px\/1.58 system-ui,-apple-system,\"Segoe UI\",sans-serif}#vbm-vref *{box-sizing:border-box}#vbm-vref 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class=\"vr-sub\">Eighty-seven reviewed terms with explicit formula assumptions, source status and non-diagnostic cautions. Editorial wording is not presented as a quotation from ISO.<\/p><div class=\"vr-tags\"><span class=\"vr-tag\">87 reviewed terms<\/span><span class=\"vr-tag\">30 scoped equations<\/span><span class=\"vr-tag\">No universal alarm table<\/span><span class=\"vr-tag\">ISO 19499 claim corrected<\/span><\/div><\/header>\n  <div class=\"vr-warning\"><strong>Reference, not diagnosis or acceptance.<\/strong> A frequency component, waveform feature or statistic is rarely unique to one fault. Do not use this glossary as an alarm table, balancing tolerance, API 670 configuration, ISO 20816 evaluation or substitute for the applicable standard and measurement procedure.<\/div>\n  <section class=\"vr-card\" aria-labelledby=\"vr-list-title\"><h2 id=\"vr-list-title\" style=\"position:absolute;left:-9999px\">Reviewed terms<\/h2><div class=\"vr-controls\"><label><span>Search all reviewed fields<\/span><input id=\"vr-search\" type=\"search\" autocomplete=\"off\" placeholder=\"e.g. RMS, bearing, orbit, ISO 20816\"><\/label><label><span>Category<\/span><select id=\"vr-category\"><option value=\"\">All categories<\/option><option value=\"Balancing\">Balancing<\/option><option value=\"Bearings\">Bearings<\/option><option value=\"Condition monitoring\">Condition monitoring<\/option><option value=\"Diagnostics\">Diagnostics<\/option><option value=\"Dynamics\">Dynamics<\/option><option value=\"Fluid machinery\">Fluid machinery<\/option><option value=\"Fundamentals\">Fundamentals<\/option><option value=\"Measurement\">Measurement<\/option><option value=\"Modal testing\">Modal testing<\/option><option value=\"Order analysis\">Order analysis<\/option><option value=\"Quantities\">Quantities<\/option><option value=\"Rotating machinery\">Rotating machinery<\/option><option value=\"Rotordynamics\">Rotordynamics<\/option><option value=\"Sensors\">Sensors<\/option><option value=\"Signal processing\">Signal processing<\/option><option value=\"Standards\">Standards<\/option><option value=\"Statistics\">Statistics<\/option><option value=\"Units\">Units<\/option><option value=\"Wave mechanics\">Wave mechanics<\/option><\/select><\/label><button id=\"vr-clear\" type=\"button\">Clear filters<\/button><\/div><div class=\"vr-letters\" aria-label=\"Filter by first character\"><button class=\"vr-letter\" type=\"button\" data-letter=\"\" aria-pressed=\"true\">All<\/button><button class=\"vr-letter\" type=\"button\" data-letter=\"#\" aria-pressed=\"false\">#<\/button><button class=\"vr-letter\" type=\"button\" data-letter=\"A\" aria-pressed=\"false\">A<\/button><button class=\"vr-letter\" type=\"button\" data-letter=\"B\" aria-pressed=\"false\">B<\/button><button class=\"vr-letter\" type=\"button\" data-letter=\"C\" aria-pressed=\"false\">C<\/button><button class=\"vr-letter\" type=\"button\" data-letter=\"D\" aria-pressed=\"false\">D<\/button><button class=\"vr-letter\" type=\"button\" data-letter=\"E\" aria-pressed=\"false\">E<\/button><button class=\"vr-letter\" type=\"button\" data-letter=\"F\" aria-pressed=\"false\">F<\/button><button class=\"vr-letter\" type=\"button\" data-letter=\"G\" aria-pressed=\"false\">G<\/button><button class=\"vr-letter\" type=\"button\" data-letter=\"H\" aria-pressed=\"false\">H<\/button><button class=\"vr-letter\" type=\"button\" data-letter=\"I\" aria-pressed=\"false\">I<\/button><button class=\"vr-letter\" type=\"button\" data-letter=\"J\" aria-pressed=\"false\">J<\/button><button class=\"vr-letter\" type=\"button\" data-letter=\"K\" aria-pressed=\"false\">K<\/button><button class=\"vr-letter\" type=\"button\" data-letter=\"L\" aria-pressed=\"false\">L<\/button><button class=\"vr-letter\" type=\"button\" data-letter=\"M\" aria-pressed=\"false\">M<\/button><button class=\"vr-letter\" type=\"button\" data-letter=\"N\" aria-pressed=\"false\">N<\/button><button class=\"vr-letter\" type=\"button\" data-letter=\"O\" aria-pressed=\"false\">O<\/button><button class=\"vr-letter\" type=\"button\" data-letter=\"P\" aria-pressed=\"false\">P<\/button><button class=\"vr-letter\" type=\"button\" data-letter=\"Q\" aria-pressed=\"false\">Q<\/button><button class=\"vr-letter\" type=\"button\" data-letter=\"R\" aria-pressed=\"false\">R<\/button><button class=\"vr-letter\" type=\"button\" data-letter=\"S\" aria-pressed=\"false\">S<\/button><button class=\"vr-letter\" type=\"button\" data-letter=\"T\" aria-pressed=\"false\">T<\/button><button class=\"vr-letter\" type=\"button\" data-letter=\"U\" aria-pressed=\"false\">U<\/button><button class=\"vr-letter\" type=\"button\" data-letter=\"V\" aria-pressed=\"false\">V<\/button><button class=\"vr-letter\" type=\"button\" data-letter=\"W\" aria-pressed=\"false\">W<\/button><button class=\"vr-letter\" type=\"button\" data-letter=\"X\" aria-pressed=\"false\">X<\/button><button class=\"vr-letter\" type=\"button\" data-letter=\"Y\" aria-pressed=\"false\">Y<\/button><button class=\"vr-letter\" type=\"button\" data-letter=\"Z\" aria-pressed=\"false\">Z<\/button><\/div><div id=\"vr-status\" class=\"vr-status\" role=\"status\" aria-live=\"polite\">Showing all 87 reviewed terms.<\/div><div id=\"vr-list\"><article class=\"vr-term\" data-letter=\"#\" data-category=\"Order analysis\" data-search=\"1\u00d7 (first order) order analysis a component whose frequency equals the instantaneous rotational reference frequency. f = 1\u00b7f\u1d63 it is common in rotating machinery but is not a unique or primary proof of unbalance. s4 s12\"><details><summary><span><strong>1\u00d7 (First Order)<\/strong><\/span><span class=\"vr-state vr-math\">VERIFIED_ENGINEERING_IDENTITY<\/span><\/summary><div class=\"vr-term-body\"><p>A component whose frequency equals the instantaneous rotational reference frequency.<\/p><pre class=\"vr-formula\">f = 1\u00b7f\u1d63<\/pre><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> It is common in rotating machinery but is not a unique or primary proof of unbalance.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S4\">S4<\/a>, <a href=\"#source-S12\">S12<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"#\" data-category=\"Order analysis\" data-search=\"2\u00d7 (second order) order analysis a component whose frequency is twice the instantaneous rotational reference frequency. f = 2\u00b7f\u1d63 it can arise from several mechanisms and is not a unique indicator of misalignment or looseness. s4 s12\"><details><summary><span><strong>2\u00d7 (Second Order)<\/strong><\/span><span class=\"vr-state vr-math\">VERIFIED_ENGINEERING_IDENTITY<\/span><\/summary><div class=\"vr-term-body\"><p>A component whose frequency is twice the instantaneous rotational reference frequency.<\/p><pre class=\"vr-formula\">f = 2\u00b7f\u1d63<\/pre><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> It can arise from several mechanisms and is not a unique indicator of misalignment or looseness.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S4\">S4<\/a>, <a href=\"#source-S12\">S12<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"A\" data-category=\"Quantities\" data-search=\"acceleration a quantities the time derivative of velocity and the second time derivative of displacement when all quantities use the same coordinate and reference frame. a(t) = dv\/dt = d\u00b2x\/dt\u00b2 a measured acceleration value also depends on the sensor, mounting, filter, bandwidth and amplitude descriptor. s10 s12\"><details><summary><span><strong>Acceleration<\/strong><small>a<\/small><\/span><span class=\"vr-state vr-math\">VERIFIED_ENGINEERING_IDENTITY<\/span><\/summary><div class=\"vr-term-body\"><p>The time derivative of velocity and the second time derivative of displacement when all quantities use the same coordinate and reference frame.<\/p><pre class=\"vr-formula\">a(t) = dv\/dt = d\u00b2x\/dt\u00b2<\/pre><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> A measured acceleration value also depends on the sensor, mounting, filter, bandwidth and amplitude descriptor.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S10\">S10<\/a>, <a href=\"#source-S12\">S12<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"A\" data-category=\"Sensors\" data-search=\"accelerometer sensors a transducer system whose primary measurand is acceleration. technology,sensitivity,frequency response,dynamic range,mounting,cross-axis response and environmental limits are model-specific; no universal 0.5hz\u201320khz range is asserted. s3\"><details><summary><span><strong>Accelerometer<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>A transducer system whose primary measurand is acceleration.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Technology,sensitivity,frequency response,dynamic range,mounting,cross-axis response and environmental limits are model-specific; no universal 0.5Hz\u201320kHz range is asserted.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S3\">S3<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"A\" data-category=\"Rotating machinery\" data-search=\"alignment rotating machinery the geometric state of machine axes or components relative to specified position and angular tolerances. a vibration pattern alone does not prove alignment or misalignment; verify geometry and the applicable coupling\/machine procedure. s3 s5\"><details><summary><span><strong>Alignment<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>The geometric state of machine axes or components relative to specified position and angular tolerances.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> A vibration pattern alone does not prove alignment or misalignment; verify geometry and the applicable coupling\/machine procedure.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S3\">S3<\/a>, <a href=\"#source-S5\">S5<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"A\" data-category=\"Quantities\" data-search=\"amplitude quantities a magnitude used to describe a signal or motion. the quantity, amplitude descriptor, reference, frequency band and processing must be stated. rms, positive peak, negative peak, maximum absolute peak and peak-to-peak are not interchangeable. s1 s10\"><details><summary><span><strong>Amplitude<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>A magnitude used to describe a signal or motion. The quantity, amplitude descriptor, reference, frequency band and processing must be stated.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> RMS, positive peak, negative peak, maximum absolute peak and peak-to-peak are not interchangeable.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S1\">S1<\/a>, <a href=\"#source-S10\">S10<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"A\" data-category=\"Bearings\" data-search=\"antifriction bearing afb (informal) bearings an older or informal label for a rolling-element bearing, such as a ball or roller bearing, contrasted with a plain or fluid-film bearing. use \u201crolling-element bearing\u201d when the bearing type matters; theoretical bearing frequencies do not by themselves prove a defect. s9\"><details><summary><span><strong>Antifriction Bearing<\/strong><small>AFB (informal)<\/small><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>An older or informal label for a rolling-element bearing, such as a ball or roller bearing, contrasted with a plain or fluid-film bearing.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Use \u201crolling-element bearing\u201d when the bearing type matters; theoretical bearing frequencies do not by themselves prove a defect.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S9\">S9<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"A\" data-category=\"Measurement\" data-search=\"axial measurement a direction parallel to a defined shaft or machine axis. an axial component can have many causes; axis, point, sensor orientation and operating state are required. s3\"><details><summary><span><strong>Axial<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>A direction parallel to a defined shaft or machine axis.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> An axial component can have many causes; axis, point, sensor orientation and operating state are required.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S3\">S3<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"B\" data-category=\"Balancing\" data-search=\"balancing balancing a process for assessing and, when required, correcting rotor mass distribution so that residual unbalance meets an applicable specification. correction-plane count and tolerance depend on rotor behaviour, configuration, service speed and the applicable part of iso 21940 or another specification. s7 s8\"><details><summary><span><strong>Balancing<\/strong><\/span><span class=\"vr-state vr-standard\">VERIFIED_OFFICIAL_STANDARD_RECORD<\/span><\/summary><div class=\"vr-term-body\"><p>A process for assessing and, when required, correcting rotor mass distribution so that residual unbalance meets an applicable specification.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Correction-plane count and tolerance depend on rotor behaviour, configuration, service speed and the applicable part of ISO 21940 or another specification.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S7\">S7<\/a>, <a href=\"#source-S8\">S8<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"B\" data-category=\"Signal processing\" data-search=\"bandwidth signal processing the interval between stated lower and upper frequency limits of a measurement, filter or analysis process. measurement bandwidth, filter bandwidth, resolution bandwidth and dft-bin spacing are different quantities. s3 s4\"><details><summary><span><strong>Bandwidth<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>The interval between stated lower and upper frequency limits of a measurement, filter or analysis process.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Measurement bandwidth, filter bandwidth, resolution bandwidth and DFT-bin spacing are different quantities.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S3\">S3<\/a>, <a href=\"#source-S4\">S4<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"B\" data-category=\"Condition monitoring\" data-search=\"baseline condition monitoring a documented reference measurement or state used for later comparison under sufficiently comparable operating and measurement conditions. a baseline is not automatically a limit; preserve point, direction, load, speed, temperature, instrument and processing records. s3 s5\"><details><summary><span><strong>Baseline<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>A documented reference measurement or state used for later comparison under sufficiently comparable operating and measurement conditions.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> A baseline is not automatically a limit; preserve point, direction, load, speed, temperature, instrument and processing records.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S3\">S3<\/a>, <a href=\"#source-S5\">S5<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"B\" data-category=\"Bearings\" data-search=\"bearing defect frequency bearings a commonly used label for a theoretical rolling-bearing kinematic frequency associated with a race, rolling element or cage. geometry, which ring rotates, contact angle and rolling assumptions matter. slip and load can shift observed components; a spectral line is not standalone defect proof. s9\"><details><summary><span><strong>Bearing Defect Frequency<\/strong><\/span><span class=\"vr-state vr-skf\">VERIFIED_MANUFACTURER_GUIDE<\/span><\/summary><div class=\"vr-term-body\"><p>A commonly used label for a theoretical rolling-bearing kinematic frequency associated with a race, rolling element or cage.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Geometry, which ring rotates, contact angle and rolling assumptions matter. Slip and load can shift observed components; a spectral line is not standalone defect proof.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S9\">S9<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"B\" data-category=\"Order analysis\" data-search=\"blade pass frequency bpf order analysis for z equally spaced blades rotating at f\u1d63 past a fixed reference,the ideal passage frequency. bpf = z f\u1d63 = z\u00b7rpm\/60 state blade count,shaft reference and geometry. a high component is not by itself proof of obstruction,resonance or blade damage. s12\"><details><summary><span><strong>Blade Pass Frequency<\/strong><small>BPF<\/small><\/span><span class=\"vr-state vr-math\">VERIFIED_ENGINEERING_IDENTITY<\/span><\/summary><div class=\"vr-term-body\"><p>For Z equally spaced blades rotating at f\u1d63 past a fixed reference,the ideal passage frequency.<\/p><pre class=\"vr-formula\">BPF = Z f\u1d63 = Z\u00b7RPM\/60<\/pre><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> State blade count,shaft reference and geometry. A high component is not by itself proof of obstruction,resonance or blade damage.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S12\">S12<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"B\" data-category=\"Bearings\" data-search=\"bpfi ball pass frequency, inner race bearings for a stationary outer ring and the stated pure-rolling geometry, the theoretical rate at which rolling elements pass a point on the inner race. bpfi = (n\/2) f\u1d63 [1 + (d\/d) cos \u03b1] n = rolling-element count; d = rolling-element diameter; d = pitch diameter; \u03b1 = contact angle; f\u1d63 = shaft rotational frequency. other ring motions require another model. s9\"><details><summary><span><strong>BPFI<\/strong><small>Ball Pass Frequency, Inner race<\/small><\/span><span class=\"vr-state vr-skf\">VERIFIED_MANUFACTURER_GUIDE<\/span><\/summary><div class=\"vr-term-body\"><p>For a stationary outer ring and the stated pure-rolling geometry, the theoretical rate at which rolling elements pass a point on the inner race.<\/p><pre class=\"vr-formula\">BPFI = (n\/2) f\u1d63 [1 + (d\/D) cos \u03b1]<\/pre><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> n = rolling-element count; d = rolling-element diameter; D = pitch diameter; \u03b1 = contact angle; f\u1d63 = shaft rotational frequency. Other ring motions require another model.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S9\">S9<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"B\" data-category=\"Bearings\" data-search=\"bpfo ball pass frequency, outer race bearings for a stationary outer ring and the stated pure-rolling geometry, the theoretical rate at which rolling elements pass a point on the outer race. bpfo = (n\/2) f\u1d63 [1 \u2212 (d\/d) cos \u03b1] the line location is an analysis overlay, not proof of an outer-race defect. confirm geometry, speed reference, sidebands, harmonics and other evidence. s9\"><details><summary><span><strong>BPFO<\/strong><small>Ball Pass Frequency, Outer race<\/small><\/span><span class=\"vr-state vr-skf\">VERIFIED_MANUFACTURER_GUIDE<\/span><\/summary><div class=\"vr-term-body\"><p>For a stationary outer ring and the stated pure-rolling geometry, the theoretical rate at which rolling elements pass a point on the outer race.<\/p><pre class=\"vr-formula\">BPFO = (n\/2) f\u1d63 [1 \u2212 (d\/D) cos \u03b1]<\/pre><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> The line location is an analysis overlay, not proof of an outer-race defect. Confirm geometry, speed reference, sidebands, harmonics and other evidence.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S9\">S9<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"B\" data-category=\"Signal processing\" data-search=\"broadband signal processing signal content distributed over a stated frequency interval rather than represented only by isolated narrow components. always state the band, filter, weighting, quantity and descriptor; \u201cbroadband\u201d alone is not a diagnosis. s3 s4\"><details><summary><span><strong>Broadband<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>Signal content distributed over a stated frequency interval rather than represented only by isolated narrow components.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Always state the band, filter, weighting, quantity and descriptor; \u201cbroadband\u201d alone is not a diagnosis.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S3\">S3<\/a>, <a href=\"#source-S4\">S4<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"B\" data-category=\"Bearings\" data-search=\"bsf ball spin frequency bearings for the stated rolling-bearing geometry, the theoretical spin frequency of a rolling element about its own axis. bsf = (d\/2d) f\u1d63 {1 \u2212 [(d\/d) cos \u03b1]\u00b2} skf distinguishes ball-defect frequency from bsf: a localized rolling-element mark can produce contacts at twice bsf. slip can shift observed components. s9\"><details><summary><span><strong>BSF<\/strong><small>Ball Spin Frequency<\/small><\/span><span class=\"vr-state vr-skf\">VERIFIED_MANUFACTURER_GUIDE<\/span><\/summary><div class=\"vr-term-body\"><p>For the stated rolling-bearing geometry, the theoretical spin frequency of a rolling element about its own axis.<\/p><pre class=\"vr-formula\">BSF = (D\/2d) f\u1d63 {1 \u2212 [(d\/D) cos \u03b1]\u00b2}<\/pre><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> SKF distinguishes ball-defect frequency from BSF: a localized rolling-element mark can produce contacts at twice BSF. Slip can shift observed components.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S9\">S9<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"C\" data-category=\"Rotordynamics\" data-search=\"campbell diagram rotordynamics a plot of measured or calculated frequency against rotational speed, often including order lines, modal branches or response amplitude. a crossing can identify a condition for further study; it does not alone prove resonance or acceptability. s4 s5\"><details><summary><span><strong>Campbell Diagram<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>A plot of measured or calculated frequency against rotational speed, often including order lines, modal branches or response amplitude.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> A crossing can identify a condition for further study; it does not alone prove resonance or acceptability.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S4\">S4<\/a>, <a href=\"#source-S5\">S5<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"C\" data-category=\"Fluid machinery\" data-search=\"cavitation fluid machinery formation and collapse or transport of vapour cavities when local liquid pressure falls sufficiently low relative to vapour pressure. noise, vibration and process changes can accompany cavitation, but broadband vibration is not unique to cavitation. s5\"><details><summary><span><strong>Cavitation<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>Formation and collapse or transport of vapour cavities when local liquid pressure falls sufficiently low relative to vapour pressure.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Noise, vibration and process changes can accompany cavitation, but broadband vibration is not unique to cavitation.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S5\">S5<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"C\" data-category=\"Condition monitoring\" data-search=\"condition monitoring condition monitoring acquisition and interpretation of information about an item or machine over time for assessment of condition and change. vibration can be one input among process,temperature,lubricant and other evidence. exact normative wording requires the licensed vocabulary. s2 s3\"><details><summary><span><strong>Condition Monitoring<\/strong><\/span><span class=\"vr-state vr-standard\">VERIFIED_OFFICIAL_STANDARD_RECORD<\/span><\/summary><div class=\"vr-term-body\"><p>Acquisition and interpretation of information about an item or machine over time for assessment of condition and change.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Vibration can be one input among process,temperature,lubricant and other evidence. Exact normative wording requires the licensed vocabulary.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S2\">S2<\/a>, <a href=\"#source-S3\">S3<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"C\" data-category=\"Rotating machinery\" data-search=\"coupling rotating machinery a mechanical element or assembly connecting shafts to transmit torque while providing the designed accommodation or constraint. coupling type,installation,load and alignment requirements are product-specific. s5\"><details><summary><span><strong>Coupling<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>A mechanical element or assembly connecting shafts to transmit torque while providing the designed accommodation or constraint.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Coupling type,installation,load and alignment requirements are product-specific.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S5\">S5<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"C\" data-category=\"Units\" data-search=\"cpm cycles per minute units a frequency expression counting cycles per minute. cpm = 60 f[hz] rpm equals cpm only for a one-cycle-per-revolution (1\u00d7) component. s12\"><details><summary><span><strong>CPM<\/strong><small>Cycles per minute<\/small><\/span><span class=\"vr-state vr-math\">VERIFIED_ENGINEERING_IDENTITY<\/span><\/summary><div class=\"vr-term-body\"><p>A frequency expression counting cycles per minute.<\/p><pre class=\"vr-formula\">CPM = 60 f[Hz]<\/pre><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> RPM equals CPM only for a one-cycle-per-revolution (1\u00d7) component.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S12\">S12<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"C\" data-category=\"Statistics\" data-search=\"crest factor statistics for a stated record and preprocessing, the maximum absolute magnitude divided by the rms magnitude. cf = max |x(t)| \/ xrms a zero-mean sine has crest factor \u221a2. no universal value such as 3.5 diagnoses bearing impacts; bandwidth, record length, clipping and transients strongly affect it. s10 s12\"><details><summary><span><strong>Crest Factor<\/strong><\/span><span class=\"vr-state vr-math\">VERIFIED_ENGINEERING_IDENTITY<\/span><\/summary><div class=\"vr-term-body\"><p>For a stated record and preprocessing, the maximum absolute magnitude divided by the RMS magnitude.<\/p><pre class=\"vr-formula\">CF = max |x(t)| \/ xRMS<\/pre><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> A zero-mean sine has crest factor \u221a2. No universal value such as 3.5 diagnoses bearing impacts; bandwidth, record length, clipping and transients strongly affect it.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S10\">S10<\/a>, <a href=\"#source-S12\">S12<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"C\" data-category=\"Rotordynamics\" data-search=\"critical speed rotordynamics a rotational speed at which a rotor-system response associated with a mode can become resonant under a particular excitation order and operating condition. it is not necessarily a single permanent number or always tied to 1\u00d7 excitation. s5\"><details><summary><span><strong>Critical Speed<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>A rotational speed at which a rotor-system response associated with a mode can become resonant under a particular excitation order and operating condition.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> It is not necessarily a single permanent number or always tied to 1\u00d7 excitation.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S5\">S5<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"D\" data-category=\"Dynamics\" data-search=\"damping dynamics mechanisms that dissipate or redistribute vibration energy and influence response amplitude, phase and decay. \u03b6 = c \/ (2\u221a(km)) the formula is only for a linear single-degree-of-freedom model with viscous damping coefficient c, stiffness k and mass m. s12\"><details><summary><span><strong>Damping<\/strong><\/span><span class=\"vr-state vr-math\">VERIFIED_ENGINEERING_IDENTITY<\/span><\/summary><div class=\"vr-term-body\"><p>Mechanisms that dissipate or redistribute vibration energy and influence response amplitude, phase and decay.<\/p><pre class=\"vr-formula\">\u03b6 = c \/ (2\u221a(km))<\/pre><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> The formula is only for a linear single-degree-of-freedom model with viscous damping coefficient c, stiffness k and mass m.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S12\">S12<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"D\" data-category=\"Signal processing\" data-search=\"demodulation signal processing signal processing that estimates information carried by modulation of another signal. rectification,envelope detection and analytic-signal methods are not interchangeable without stated filters,bandwidth and scaling. s4\"><details><summary><span><strong>Demodulation<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>Signal processing that estimates information carried by modulation of another signal.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Rectification,envelope detection and analytic-signal methods are not interchangeable without stated filters,bandwidth and scaling.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S4\">S4<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"D\" data-category=\"Quantities\" data-search=\"displacement quantities change of position relative to a stated reference. in machinery work it can be absolute motion, relative shaft-to-bearing motion, or one coordinate of an orbit. example sine: x(t) = x sin(\u03c9t + \u03c6) state axis, reference, amplitude descriptor and whether the value is scalar, waveform or two-channel orbit data. s10 s12\"><details><summary><span><strong>Displacement<\/strong><\/span><span class=\"vr-state vr-math\">VERIFIED_ENGINEERING_IDENTITY<\/span><\/summary><div class=\"vr-term-body\"><p>Change of position relative to a stated reference. In machinery work it can be absolute motion, relative shaft-to-bearing motion, or one coordinate of an orbit.<\/p><pre class=\"vr-formula\">Example sine: x(t) = X sin(\u03c9t + \u03c6)<\/pre><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> State axis, reference, amplitude descriptor and whether the value is scalar, waveform or two-channel orbit data.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S10\">S10<\/a>, <a href=\"#source-S12\">S12<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"E\" data-category=\"Rotating machinery\" data-search=\"eccentricity rotating machinery separation between specified geometric, rotation or mass-centre axes or centres. geometric eccentricity, mass eccentricity, electrical runout and indicated runout are different. in an ideal point-unbalance model u = m e only when u and m use consistent definitions. s7\"><details><summary><span><strong>Eccentricity<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>Separation between specified geometric, rotation or mass-centre axes or centres.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Geometric eccentricity, mass eccentricity, electrical runout and indicated runout are different. In an ideal point-unbalance model U = m e only when U and m use consistent definitions.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S7\">S7<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"E\" data-category=\"Signal processing\" data-search=\"envelope analysis signal processing demodulation of amplitude variation from a selected carrier band, often after band-pass filtering and rectification or analytic-signal processing. report sensor, carrier band, filter, demodulation method, sampling and speed. it does not automatically prove a rolling-bearing defect. s4 s5 s9\"><details><summary><span><strong>Envelope Analysis<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>Demodulation of amplitude variation from a selected carrier band, often after band-pass filtering and rectification or analytic-signal processing.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Report sensor, carrier band, filter, demodulation method, sampling and speed. It does not automatically prove a rolling-bearing defect.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S4\">S4<\/a>, <a href=\"#source-S5\">S5<\/a>, <a href=\"#source-S9\">S9<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"F\" data-category=\"Signal processing\" data-search=\"fft fast fourier transform signal processing a family of algorithms that efficiently computes a discrete fourier transform. the displayed spectrum also depends on sampling, record length, window, scaling, averaging and leakage; fft output is not an infinitely resolved continuous spectrum. s4 s12\"><details><summary><span><strong>FFT<\/strong><small>Fast Fourier Transform<\/small><\/span><span class=\"vr-state vr-math\">VERIFIED_ENGINEERING_IDENTITY<\/span><\/summary><div class=\"vr-term-body\"><p>A family of algorithms that efficiently computes a discrete Fourier transform.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> The displayed spectrum also depends on sampling, record length, window, scaling, averaging and leakage; FFT output is not an infinitely resolved continuous spectrum.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S4\">S4<\/a>, <a href=\"#source-S12\">S12<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"F\" data-category=\"Quantities\" data-search=\"frequency f quantities rate of repetition of a periodic phenomenon, expressed in hertz when measured in cycles per second. f = 1\/t the period relation applies to a periodic component with period t. s1 s12\"><details><summary><span><strong>Frequency<\/strong><small>f<\/small><\/span><span class=\"vr-state vr-math\">VERIFIED_ENGINEERING_IDENTITY<\/span><\/summary><div class=\"vr-term-body\"><p>Rate of repetition of a periodic phenomenon, expressed in hertz when measured in cycles per second.<\/p><pre class=\"vr-formula\">f = 1\/T<\/pre><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> The period relation applies to a periodic component with period T.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S1\">S1<\/a>, <a href=\"#source-S12\">S12<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"F\" data-category=\"Bearings\" data-search=\"ftf fundamental train frequency bearings for the stated bearing model, the theoretical rotational frequency of the cage or rolling-element train. ftf = (1\/2) f\u1d63 [1 \u2212 (d\/d) cos \u03b1] do not replace the geometry with a universal fraction of shaft speed; ring motion and slip affect the value. s9\"><details><summary><span><strong>FTF<\/strong><small>Fundamental Train Frequency<\/small><\/span><span class=\"vr-state vr-skf\">VERIFIED_MANUFACTURER_GUIDE<\/span><\/summary><div class=\"vr-term-body\"><p>For the stated bearing model, the theoretical rotational frequency of the cage or rolling-element train.<\/p><pre class=\"vr-formula\">FTF = (1\/2) f\u1d63 [1 \u2212 (d\/D) cos \u03b1]<\/pre><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Do not replace the geometry with a universal fraction of shaft speed; ring motion and slip affect the value.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S9\">S9<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"G\" data-category=\"Units\" data-search=\"g-value g\u2099 ratio units an acceleration magnitude expressed as a ratio to the conventional standard acceleration g\u2099. 1 g\u2099 = 9.80665 m\/s\u00b2 exactly this is a reference conversion, not local gravitational acceleration and not a vibration-severity category. s11\"><details><summary><span><strong>g-value<\/strong><small>g\u2099 ratio<\/small><\/span><span class=\"vr-state vr-metrology\">VERIFIED_OFFICIAL_METROLOGY<\/span><\/summary><div class=\"vr-term-body\"><p>An acceleration magnitude expressed as a ratio to the conventional standard acceleration g\u2099.<\/p><pre class=\"vr-formula\">1 g\u2099 = 9.80665 m\/s\u00b2 exactly<\/pre><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> This is a reference conversion, not local gravitational acceleration and not a vibration-severity category.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S11\">S11<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"G\" data-category=\"Order analysis\" data-search=\"gear mesh frequency gmf order analysis for a gear with z teeth rotating at f\u1d63, the ideal tooth-engagement repetition frequency. gmf = z f\u1d63 = z\u00b7rpm\/60 observed components and sidebands depend on geometry,load,speed variation and measurement path; they are not standalone damage proof. s12\"><details><summary><span><strong>Gear Mesh Frequency<\/strong><small>GMF<\/small><\/span><span class=\"vr-state vr-math\">VERIFIED_ENGINEERING_IDENTITY<\/span><\/summary><div class=\"vr-term-body\"><p>For a gear with Z teeth rotating at f\u1d63, the ideal tooth-engagement repetition frequency.<\/p><pre class=\"vr-formula\">GMF = Z f\u1d63 = Z\u00b7RPM\/60<\/pre><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Observed components and sidebands depend on geometry,load,speed variation and measurement path; they are not standalone damage proof.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S12\">S12<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"H\" data-category=\"Signal processing\" data-search=\"harmonic signal processing a component whose frequency is an integer multiple of a stated fundamental frequency. harmonics can arise from waveform shape, nonlinearity, modulation and many mechanisms; they are not a unique fault signature. s4\"><details><summary><span><strong>Harmonic<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>A component whose frequency is an integer multiple of a stated fundamental frequency.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Harmonics can arise from waveform shape, nonlinearity, modulation and many mechanisms; they are not a unique fault signature.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S4\">S4<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"H\" data-category=\"Signal processing\" data-search=\"high-frequency detection hfd (method-dependent) signal processing a vendor- or procedure-specific label for measuring or processing a selected high-frequency band. there is no universal 5\u201360khz hfd band. report sensor,band,filter,detector,units and reference procedure. s4 s5\"><details><summary><span><strong>High-Frequency Detection<\/strong><small>HFD (method-dependent)<\/small><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>A vendor- or procedure-specific label for measuring or processing a selected high-frequency band.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> There is no universal 5\u201360kHz HFD band. Report sensor,band,filter,detector,units and reference procedure.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S4\">S4<\/a>, <a href=\"#source-S5\">S5<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"H\" data-category=\"Units\" data-search=\"hz hertz units the si derived unit for frequency, equal to reciprocal seconds. 1 hz = 1 s\u207b\u00b9 = 60 cpm state the physical phenomenon whose frequency is being reported. s11 s12\"><details><summary><span><strong>Hz<\/strong><small>hertz<\/small><\/span><span class=\"vr-state vr-metrology\">VERIFIED_OFFICIAL_METROLOGY<\/span><\/summary><div class=\"vr-term-body\"><p>The SI derived unit for frequency, equal to reciprocal seconds.<\/p><pre class=\"vr-formula\">1 Hz = 1 s\u207b\u00b9 = 60 CPM<\/pre><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> State the physical phenomenon whose frequency is being reported.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S11\">S11<\/a>, <a href=\"#source-S12\">S12<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"I\" data-category=\"Balancing\" data-search=\"imbalance balancing a common informal synonym for unbalance. iso rotor-balancing work uses the term \u201cunbalance\u201d; exact normative wording requires the licensed vocabulary. this glossary uses \u201cunbalance\u201d for the mass-distribution quantity. s7\"><details><summary><span><strong>Imbalance<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>A common informal synonym for unbalance. ISO rotor-balancing work uses the term \u201cunbalance\u201d; exact normative wording requires the licensed vocabulary.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> This glossary uses \u201cunbalance\u201d for the mass-distribution quantity.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S7\">S7<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"I\" data-category=\"Modal testing\" data-search=\"impact test modal testing a dynamic test using a measured impact input and measured response to estimate frequency-response or modal information. an unmeasured \u201cbump test\u201d is not equivalent to a calibrated modal test; windowing,coherence,force spectrum and boundary conditions matter. s5\"><details><summary><span><strong>Impact Test<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>A dynamic test using a measured impact input and measured response to estimate frequency-response or modal information.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> An unmeasured \u201cbump test\u201d is not equivalent to a calibrated modal test; windowing,coherence,force spectrum and boundary conditions matter.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S5\">S5<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"I\" data-category=\"Standards\" data-search=\"iso 10816 standards a legacy multi-part family for evaluating machine vibration measured on non-rotating parts. parts have different life-cycle states and many have corresponding iso 20816 replacements. never cite \u201ciso 10816\u201d without the exact part,edition,machine scope,quantity,point,band and support condition. s6\"><details><summary><span><strong>ISO 10816<\/strong><\/span><span class=\"vr-state vr-standard\">VERIFIED_OFFICIAL_STANDARD_RECORD<\/span><\/summary><div class=\"vr-term-body\"><p>A legacy multi-part family for evaluating machine vibration measured on non-rotating parts. Parts have different life-cycle states and many have corresponding ISO 20816 replacements.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Never cite \u201cISO 10816\u201d without the exact part,edition,machine scope,quantity,point,band and support condition.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S6\">S6<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"I\" data-category=\"Standards\" data-search=\"iso 20816 standards a multi-part family titled \u201cmeasurement and evaluation of machine vibration\u201d. iso 20816-1:2016 is the published general-guidelines edition and is marked for revision. the family permits different well-defined quantities and methods. it does not supply one universal broadband-velocity table for every machine. s6\"><details><summary><span><strong>ISO 20816<\/strong><\/span><span class=\"vr-state vr-standard\">VERIFIED_OFFICIAL_STANDARD_RECORD<\/span><\/summary><div class=\"vr-term-body\"><p>A multi-part family titled \u201cMeasurement and evaluation of machine vibration\u201d. ISO 20816-1:2016 is the published general-guidelines edition and is marked for revision.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> The family permits different well-defined quantities and methods. It does not supply one universal broadband-velocity table for every machine.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S6\">S6<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"I\" data-category=\"Standards\" data-search=\"iso 21940 standards the rotor-balancing series. iso 21940-1:2019 is the current introduction; iso 21940-11:2016 plus amendment 1:2022 addresses procedures and tolerances for rotors with rigid behaviour. do not transfer quality grades or tolerances to a rotor without the applicable part,rotor behaviour and service-speed context. iso 19499:2007 is withdrawn. s7 s8\"><details><summary><span><strong>ISO 21940<\/strong><\/span><span class=\"vr-state vr-standard\">VERIFIED_OFFICIAL_STANDARD_RECORD<\/span><\/summary><div class=\"vr-term-body\"><p>The rotor-balancing series. ISO 21940-1:2019 is the current introduction; ISO 21940-11:2016 plus Amendment 1:2022 addresses procedures and tolerances for rotors with rigid behaviour.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Do not transfer quality grades or tolerances to a rotor without the applicable part,rotor behaviour and service-speed context. ISO 19499:2007 is withdrawn.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S7\">S7<\/a>, <a href=\"#source-S8\">S8<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"J\" data-category=\"Quantities\" data-search=\"jerk quantities time derivative of acceleration and third time derivative of displacement when the derivatives share one coordinate and reference. j(t) = da\/dt = d\u00b3x\/dt\u00b3 numerical differentiation amplifies high-frequency noise; report filtering and bandwidth. s12\"><details><summary><span><strong>Jerk<\/strong><\/span><span class=\"vr-state vr-math\">VERIFIED_ENGINEERING_IDENTITY<\/span><\/summary><div class=\"vr-term-body\"><p>Time derivative of acceleration and third time derivative of displacement when the derivatives share one coordinate and reference.<\/p><pre class=\"vr-formula\">j(t) = da\/dt = d\u00b3x\/dt\u00b3<\/pre><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Numerical differentiation amplifies high-frequency noise; report filtering and bandwidth.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S12\">S12<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"J\" data-category=\"Bearings\" data-search=\"journal bearing bearings a plain bearing in which a journal is supported by a sliding interface,commonly with a lubricating film. bearing type,load,clearance,lubricant and dynamic coefficients determine stability; not every journal bearing exhibits oil whirl or oil whip. s5\"><details><summary><span><strong>Journal Bearing<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>A plain bearing in which a journal is supported by a sliding interface,commonly with a lubricating film.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Bearing type,load,clearance,lubricant and dynamic coefficients determine stability; not every journal bearing exhibits oil whirl or oil whip.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S5\">S5<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"K\" data-category=\"Sensors\" data-search=\"keyphasor phase-reference signal sensors a once-per-revolution or otherwise defined shaft-reference signal used for speed,phase or order tracking. pulse geometry,latency,polarity,missing pulses and reference angle must be documented. a phase reference does not itself locate a heavy spot. s3 s4\"><details><summary><span><strong>Keyphasor<\/strong><small>phase-reference signal<\/small><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>A once-per-revolution or otherwise defined shaft-reference signal used for speed,phase or order tracking.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Pulse geometry,latency,polarity,missing pulses and reference angle must be documented. A phase reference does not itself locate a heavy spot.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S3\">S3<\/a>, <a href=\"#source-S4\">S4<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"K\" data-category=\"Statistics\" data-search=\"kurtosis statistics a normalized fourth central moment of a distribution or sampled record. pearson kurtosis for an ideal gaussian distribution is 3; excess kurtosis is pearson kurtosis minus 3. state convention,record length,band and preprocessing. no universal threshold such as 4 diagnoses a particular defect. s12\"><details><summary><span><strong>Kurtosis<\/strong><\/span><span class=\"vr-state vr-math\">VERIFIED_ENGINEERING_IDENTITY<\/span><\/summary><div class=\"vr-term-body\"><p>A normalized fourth central moment of a distribution or sampled record. Pearson kurtosis for an ideal Gaussian distribution is 3; excess kurtosis is Pearson kurtosis minus 3.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> State convention,record length,band and preprocessing. No universal threshold such as 4 diagnoses a particular defect.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S12\">S12<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"L\" data-category=\"Dynamics\" data-search=\"logarithmic decrement \u03b4 dynamics natural logarithm of the ratio of same-direction amplitudes separated by one or more cycles in a decaying response. \u03b4 = (1\/n) ln(x\u2096\/x\u2096\u208a\u2099);  \u03b4 = 2\u03c0\u03b6\/\u221a(1\u2212\u03b6\u00b2) the \u03b6 relation assumes an underdamped linear single-degree-of-freedom system with viscous damping. s12\"><details><summary><span><strong>Logarithmic Decrement<\/strong><small>\u03b4<\/small><\/span><span class=\"vr-state vr-math\">VERIFIED_ENGINEERING_IDENTITY<\/span><\/summary><div class=\"vr-term-body\"><p>Natural logarithm of the ratio of same-direction amplitudes separated by one or more cycles in a decaying response.<\/p><pre class=\"vr-formula\">\u03b4 = (1\/n) ln(x\u2096\/x\u2096\u208a\u2099);  \u03b4 = 2\u03c0\u03b6\/\u221a(1\u2212\u03b6\u00b2)<\/pre><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> The \u03b6 relation assumes an underdamped linear single-degree-of-freedom system with viscous damping.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S12\">S12<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"L\" data-category=\"Diagnostics\" data-search=\"looseness diagnostics loss or variation of an intended mechanical constraint,fit,preload or support condition. harmonics,subharmonics or waveform clipping are possible observations,not standalone proof; inspect the joint and operating condition. s5\"><details><summary><span><strong>Looseness<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>Loss or variation of an intended mechanical constraint,fit,preload or support condition.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Harmonics,subharmonics or waveform clipping are possible observations,not standalone proof; inspect the joint and operating condition.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S5\">S5<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"M\" data-category=\"Diagnostics\" data-search=\"misalignment diagnostics a geometric condition in which intended coupled or supported axes do not meet the applicable offset,angular or positional requirement. axial,radial,1\u00d7 and 2\u00d7 components are non-unique observations. confirm by geometry and machine-specific evidence. s5\"><details><summary><span><strong>Misalignment<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>A geometric condition in which intended coupled or supported axes do not meet the applicable offset,angular or positional requirement.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Axial,radial,1\u00d7 and 2\u00d7 components are non-unique observations. Confirm by geometry and machine-specific evidence.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S5\">S5<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"M\" data-category=\"Modal testing\" data-search=\"modal analysis modal testing identification or calculation of modal properties such as natural frequencies,damping and mode shapes for a stated system and boundary condition. experimental and analytical modal models require validation and uncertainty records. s5\"><details><summary><span><strong>Modal Analysis<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>Identification or calculation of modal properties such as natural frequencies,damping and mode shapes for a stated system and boundary condition.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Experimental and analytical modal models require validation and uncertainty records.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S5\">S5<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"N\" data-category=\"Dynamics\" data-search=\"natural frequency f\u2099 dynamics a modal frequency of free vibration for a specified system and boundary condition. undamped sdof: f\u2099 = (1\/2\u03c0) \u221a(k\/m) real machines have multiple modes and frequency-dependent,boundary-dependent properties; the formula is not a general machine model. s12\"><details><summary><span><strong>Natural Frequency<\/strong><small>f\u2099<\/small><\/span><span class=\"vr-state vr-math\">VERIFIED_ENGINEERING_IDENTITY<\/span><\/summary><div class=\"vr-term-body\"><p>A modal frequency of free vibration for a specified system and boundary condition.<\/p><pre class=\"vr-formula\">Undamped SDOF: f\u2099 = (1\/2\u03c0) \u221a(k\/m)<\/pre><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Real machines have multiple modes and frequency-dependent,boundary-dependent properties; the formula is not a general machine model.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S12\">S12<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"O\" data-category=\"Units\" data-search=\"octave units a frequency ratio of 2:1. fractional-octave bands require stated centre-frequency and band-edge conventions. f\u2082\/f\u2081 = 2 for one octave an octave is a ratio,not an absolute bandwidth or diagnostic criterion. s12\"><details><summary><span><strong>Octave<\/strong><\/span><span class=\"vr-state vr-math\">VERIFIED_ENGINEERING_IDENTITY<\/span><\/summary><div class=\"vr-term-body\"><p>A frequency ratio of 2:1. Fractional-octave bands require stated centre-frequency and band-edge conventions.<\/p><pre class=\"vr-formula\">f\u2082\/f\u2081 = 2 for one octave<\/pre><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> An octave is a ratio,not an absolute bandwidth or diagnostic criterion.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S12\">S12<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"O\" data-category=\"Rotordynamics\" data-search=\"oil whip rotordynamics a fluid-induced rotor instability in which a subsynchronous response can become associated with a rotor mode over a speed range. no universal \u201cabove 2\u00d7 critical speed\u201d rule is published here; verify the rotor-bearing model and operating evidence. s5\"><details><summary><span><strong>Oil Whip<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>A fluid-induced rotor instability in which a subsynchronous response can become associated with a rotor mode over a speed range.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> No universal \u201cabove 2\u00d7 critical speed\u201d rule is published here; verify the rotor-bearing model and operating evidence.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S5\">S5<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"O\" data-category=\"Rotordynamics\" data-search=\"oil whirl rotordynamics a fluid-induced subsynchronous precessional response associated with a fluid-film bearing system. frequency ratio and onset are machine-dependent; do not use a universal 0.42\u20130.48\u00d7 band as a diagnosis. s5\"><details><summary><span><strong>Oil Whirl<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>A fluid-induced subsynchronous precessional response associated with a fluid-film bearing system.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Frequency ratio and onset are machine-dependent; do not use a universal 0.42\u20130.48\u00d7 band as a diagnosis.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S5\">S5<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"O\" data-category=\"Measurement\" data-search=\"orbit measurement the locus of shaft or rotor position in a transverse plane,constructed from two simultaneous displacement channels and their geometry. state whether motion is relative or absolute,probe angles,polarity,filtering,runout compensation and phase reference. shape alone is not a unique fault diagnosis. s3\"><details><summary><span><strong>Orbit<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>The locus of shaft or rotor position in a transverse plane,constructed from two simultaneous displacement channels and their geometry.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> State whether motion is relative or absolute,probe angles,polarity,filtering,runout compensation and phase reference. Shape alone is not a unique fault diagnosis.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S3\">S3<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"O\" data-category=\"Measurement\" data-search=\"orbit plot measurement a display of one transverse displacement channel against another to show a shaft or rotor locus. see orbit. probe geometry,relative\/absolute reference,filter,runout compensation and direction convention are essential. s3\"><details><summary><span><strong>Orbit Plot<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>A display of one transverse displacement channel against another to show a shaft or rotor locus.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> See Orbit. Probe geometry,relative\/absolute reference,filter,runout compensation and direction convention are essential.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S3\">S3<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"O\" data-category=\"Signal processing\" data-search=\"orders signal processing frequency normalized by a rotational reference. order k means f = k f\u1d63 at that operating instant. order k = f\/f\u1d63 the order number is dimensionless; its frequency in hertz changes with rotational speed. s4 s12\"><details><summary><span><strong>Orders<\/strong><\/span><span class=\"vr-state vr-math\">VERIFIED_ENGINEERING_IDENTITY<\/span><\/summary><div class=\"vr-term-body\"><p>Frequency normalized by a rotational reference. Order k means f = k f\u1d63 at that operating instant.<\/p><pre class=\"vr-formula\">order k = f\/f\u1d63<\/pre><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> The order number is dimensionless; its frequency in hertz changes with rotational speed.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S4\">S4<\/a>, <a href=\"#source-S12\">S12<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"O\" data-category=\"Measurement\" data-search=\"overall level measurement an aggregate signal magnitude over a stated measurement chain and frequency band. state quantity,descriptor,band,filter,point,direction and operating state. it is not universally velocity rms or 10\u20131000 hz. s3 s6\"><details><summary><span><strong>Overall Level<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>An aggregate signal magnitude over a stated measurement chain and frequency band.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> State quantity,descriptor,band,filter,point,direction and operating state. It is not universally velocity RMS or 10\u20131000 Hz.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S3\">S3<\/a>, <a href=\"#source-S6\">S6<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"P\" data-category=\"Statistics\" data-search=\"peak pk statistics a stated extreme of a record:positive peak,negative peak or maximum absolute peak must be distinguished. zero-mean sine: xpeak = \u221a2 xrms the \u221a2 relation is not valid for arbitrary waveform peaks. s10 s12\"><details><summary><span><strong>Peak<\/strong><small>Pk<\/small><\/span><span class=\"vr-state vr-math\">VERIFIED_ENGINEERING_IDENTITY<\/span><\/summary><div class=\"vr-term-body\"><p>A stated extreme of a record:positive peak,negative peak or maximum absolute peak must be distinguished.<\/p><pre class=\"vr-formula\">Zero-mean sine: Xpeak = \u221a2 XRMS<\/pre><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> The \u221a2 relation is not valid for arbitrary waveform peaks.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S10\">S10<\/a>, <a href=\"#source-S12\">S12<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"P\" data-category=\"Statistics\" data-search=\"peak-to-peak pk\u2013pk statistics difference between the maximum and minimum values in a stated record. xpk-pk = xmax \u2212 xmin it equals twice the absolute peak only for a waveform symmetric about the stated reference. s10 s12\"><details><summary><span><strong>Peak-to-Peak<\/strong><small>Pk\u2013Pk<\/small><\/span><span class=\"vr-state vr-math\">VERIFIED_ENGINEERING_IDENTITY<\/span><\/summary><div class=\"vr-term-body\"><p>Difference between the maximum and minimum values in a stated record.<\/p><pre class=\"vr-formula\">Xpk-pk = xmax \u2212 xmin<\/pre><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> It equals twice the absolute peak only for a waveform symmetric about the stated reference.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S10\">S10<\/a>, <a href=\"#source-S12\">S12<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"P\" data-category=\"Signal processing\" data-search=\"phase \u03c6 signal processing angular or time relationship between components at a stated frequency and a stated reference. reference location,polarity,rotation convention,filter and time synchronization are required. phase does not directly equal a rotor heavy-spot angle. s4 s10\"><details><summary><span><strong>Phase<\/strong><small>\u03c6<\/small><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>Angular or time relationship between components at a stated frequency and a stated reference.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Reference location,polarity,rotation convention,filter and time synchronization are required. Phase does not directly equal a rotor heavy-spot angle.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S4\">S4<\/a>, <a href=\"#source-S10\">S10<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"P\" data-category=\"Sensors\" data-search=\"proximity probe sensors a non-contact displacement transducer system,often eddy-current,used to measure probe-to-target gap and dynamic relative motion. sensitivity,linear range,target material,cable\/driver combination and installation are system-specific. no universal api 670 sensitivity is asserted. s3\"><details><summary><span><strong>Proximity Probe<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>A non-contact displacement transducer system,often eddy-current,used to measure probe-to-target gap and dynamic relative motion.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Sensitivity,linear range,target material,cable\/driver combination and installation are system-specific. No universal API 670 sensitivity is asserted.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S3\">S3<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"R\" data-category=\"Measurement\" data-search=\"radial measurement a direction perpendicular to a defined shaft or rotation axis. horizontal and vertical are installation coordinates,not universal fault labels; record probe angle and positive direction. s3\"><details><summary><span><strong>Radial<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>A direction perpendicular to a defined shaft or rotation axis.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Horizontal and vertical are installation coordinates,not universal fault labels; record probe angle and positive direction.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S3\">S3<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"R\" data-category=\"Dynamics\" data-search=\"resonance dynamics a condition in which forcing near a modal frequency produces a response strongly influenced by that mode. amplification and phase depend on damping,forcing,nonlinearity and boundary conditions; frequency coincidence alone is not a complete assessment. s12\"><details><summary><span><strong>Resonance<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>A condition in which forcing near a modal frequency produces a response strongly influenced by that mode.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Amplification and phase depend on damping,forcing,nonlinearity and boundary conditions; frequency coincidence alone is not a complete assessment.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S12\">S12<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"R\" data-category=\"Statistics\" data-search=\"rms root mean square statistics square root of the mean of squared values over a stated record or interval. xrms = \u221a[(1\/(t\u2082\u2212t\u2081)) \u222b\u209c\u2081\u1d57\u2082 x\u00b2(t) dt] for a zero-mean sine xrms = xpeak\/\u221a2. rms is not by itself \u201cenergy content\u201d or a universal severity measure. s10 s12\"><details><summary><span><strong>RMS<\/strong><small>root mean square<\/small><\/span><span class=\"vr-state vr-math\">VERIFIED_ENGINEERING_IDENTITY<\/span><\/summary><div class=\"vr-term-body\"><p>Square root of the mean of squared values over a stated record or interval.<\/p><pre class=\"vr-formula\">xRMS = \u221a[(1\/(t\u2082\u2212t\u2081)) \u222b\u209c\u2081\u1d57\u2082 x\u00b2(t) dt]<\/pre><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> For a zero-mean sine XRMS = Xpeak\/\u221a2. RMS is not by itself \u201cenergy content\u201d or a universal severity measure.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S10\">S10<\/a>, <a href=\"#source-S12\">S12<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"R\" data-category=\"Rotating machinery\" data-search=\"rotor rotating machinery the rotating assembly or component considered in a machine model or balancing procedure. define what is included in the rotor and its service\/boundary conditions. s7\"><details><summary><span><strong>Rotor<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>The rotating assembly or component considered in a machine model or balancing procedure.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Define what is included in the rotor and its service\/boundary conditions.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S7\">S7<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"R\" data-category=\"Units\" data-search=\"rpm revolutions per minute units rotational rate expressed as revolutions per minute. 1\u00d7 rotational frequency f\u1d63[hz] = rpm\/60 only a one-cycle-per-revolution component equals rpm in cpm; other orders and event counts differ. s12\"><details><summary><span><strong>RPM<\/strong><small>revolutions per minute<\/small><\/span><span class=\"vr-state vr-math\">VERIFIED_ENGINEERING_IDENTITY<\/span><\/summary><div class=\"vr-term-body\"><p>Rotational rate expressed as revolutions per minute.<\/p><pre class=\"vr-formula\">1\u00d7 rotational frequency f\u1d63[Hz] = RPM\/60<\/pre><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Only a one-cycle-per-revolution component equals RPM in CPM; other orders and event counts differ.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S12\">S12<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"R\" data-category=\"Measurement\" data-search=\"runout measurement apparent variation associated with target geometry,shaft motion,target electrical properties or the measurement system as the shaft turns. mechanical and electrical runout require a defined measurement and compensation procedure. do not blindly subtract a tir value from dynamic vibration. s3\"><details><summary><span><strong>Runout<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>Apparent variation associated with target geometry,shaft motion,target electrical properties or the measurement system as the shaft turns.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Mechanical and electrical runout require a defined measurement and compensation procedure. Do not blindly subtract a TIR value from dynamic vibration.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S3\">S3<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"S\" data-category=\"Rotating machinery\" data-search=\"shaft rotating machinery a rotating member used to transmit torque or support rotating components. straightness,surface,material,loading,boundary conditions and cracks require their own measurements; vibration alone does not define shaft condition. s7\"><details><summary><span><strong>Shaft<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>A rotating member used to transmit torque or support rotating components.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Straightness,surface,material,loading,boundary conditions and cracks require their own measurements; vibration alone does not define shaft condition.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S7\">S7<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"S\" data-category=\"Signal processing\" data-search=\"sideband signal processing a component adjacent to a carrier or principal component,with spacing associated with modulation or another periodic process. state carrier,spacing,orders and operating condition. sidebands are not unique proof of gear,bearing or electrical damage. s4\"><details><summary><span><strong>Sideband<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>A component adjacent to a carrier or principal component,with spacing associated with modulation or another periodic process.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> State carrier,spacing,orders and operating condition. Sidebands are not unique proof of gear,bearing or electrical damage.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S4\">S4<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"S\" data-category=\"Signal processing\" data-search=\"spectrum signal processing a representation of signal magnitude,phase or power-related quantity versus frequency. state transform,scaling,units,window,record length,averaging,bandwidth and frequency resolution. s4\"><details><summary><span><strong>Spectrum<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>A representation of signal magnitude,phase or power-related quantity versus frequency.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> State transform,scaling,units,window,record length,averaging,bandwidth and frequency resolution.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S4\">S4<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"S\" data-category=\"Signal processing\" data-search=\"subharmonic signal processing a component at a rational fraction of a stated fundamental or reference frequency. a subharmonic is a frequency relation,not a unique diagnosis of looseness,whirl,rub or belt behaviour. s4\"><details><summary><span><strong>Subharmonic<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>A component at a rational fraction of a stated fundamental or reference frequency.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> A subharmonic is a frequency relation,not a unique diagnosis of looseness,whirl,rub or belt behaviour.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S4\">S4<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"S\" data-category=\"Signal processing\" data-search=\"synchronous signal processing phase-coherent with a stated rotational reference. some practices use \u201csynchronous\u201d for integer orders; others reserve it for 1\u00d7,so the convention must be stated. do not assume every synchronous component has the same cause. s4\"><details><summary><span><strong>Synchronous<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>Phase-coherent with a stated rotational reference. Some practices use \u201csynchronous\u201d for integer orders; others reserve it for 1\u00d7,so the convention must be stated.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Do not assume every synchronous component has the same cause.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S4\">S4<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"T\" data-category=\"Signal processing\" data-search=\"time waveform signal processing recorded signal value versus time. it is the output of a measurement chain,not automatically the true mechanical motion. state sampling,units,filtering,range and sensor orientation. s4\"><details><summary><span><strong>Time Waveform<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>Recorded signal value versus time.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> It is the output of a measurement chain,not automatically the true mechanical motion. State sampling,units,filtering,range and sensor orientation.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S4\">S4<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"T\" data-category=\"Quantities\" data-search=\"torsional vibration quantities oscillatory variation of angular position,angular velocity or torque about a shaft axis. it requires a suitable torsional measurement or model. ordinary transverse accelerometers and radial proximity probes do not directly measure torsional motion,although coupled responses can occur. s6\"><details><summary><span><strong>Torsional Vibration<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>Oscillatory variation of angular position,angular velocity or torque about a shaft axis.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> It requires a suitable torsional measurement or model. Ordinary transverse accelerometers and radial proximity probes do not directly measure torsional motion,although coupled responses can occur.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S6\">S6<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"T\" data-category=\"Dynamics\" data-search=\"transmissibility dynamics a ratio of response to input under a precisely defined excitation and output convention. base-displacement sdof: |x\/y| = \u221a[(1+(2\u03b6r)\u00b2)\/((1\u2212r\u00b2)\u00b2+(2\u03b6r)\u00b2)], r=f\/f\u2099 the previous page omitted the numerator. force,base-motion,relative-motion and acceleration transmissibilities use different definitions. s12\"><details><summary><span><strong>Transmissibility<\/strong><\/span><span class=\"vr-state vr-math\">VERIFIED_ENGINEERING_IDENTITY<\/span><\/summary><div class=\"vr-term-body\"><p>A ratio of response to input under a precisely defined excitation and output convention.<\/p><pre class=\"vr-formula\">Base-displacement SDOF: |X\/Y| = \u221a[(1+(2\u03b6r)\u00b2)\/((1\u2212r\u00b2)\u00b2+(2\u03b6r)\u00b2)], r=f\/f\u2099<\/pre><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> The previous page omitted the numerator. Force,base-motion,relative-motion and acceleration transmissibilities use different definitions.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S12\">S12<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"T\" data-category=\"Condition monitoring\" data-search=\"trend condition monitoring a time-ordered series of comparable measurements used to examine change. comparable point,direction,sensor,band,load,speed and processing are required. a trend change is evidence for review,not an automatic failure forecast. s3 s5\"><details><summary><span><strong>Trend<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>A time-ordered series of comparable measurements used to examine change.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Comparable point,direction,sensor,band,load,speed and processing are required. A trend change is evidence for review,not an automatic failure forecast.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S3\">S3<\/a>, <a href=\"#source-S5\">S5<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"U\" data-category=\"Balancing\" data-search=\"unbalance balancing a rotor mass-distribution condition for which the principal inertia axis does not coincide with the rotation axis as required by the model. ideal unbalance-force magnitude: f = u\u03c9\u00b2 = m e \u03c9\u00b2 the force identity is an ideal rotating-unbalance model. a measured 1\u00d7 component is not unique proof or a complete balance tolerance. s7 s12\"><details><summary><span><strong>Unbalance<\/strong><\/span><span class=\"vr-state vr-math\">VERIFIED_ENGINEERING_IDENTITY<\/span><\/summary><div class=\"vr-term-body\"><p>A rotor mass-distribution condition for which the principal inertia axis does not coincide with the rotation axis as required by the model.<\/p><pre class=\"vr-formula\">Ideal unbalance-force magnitude: F = U\u03c9\u00b2 = m e \u03c9\u00b2<\/pre><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> The force identity is an ideal rotating-unbalance model. A measured 1\u00d7 component is not unique proof or a complete balance tolerance.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S7\">S7<\/a>, <a href=\"#source-S12\">S12<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"V\" data-category=\"Order analysis\" data-search=\"vane pass frequency vpf order analysis for z equally spaced vanes rotating at f\u1d63 past a fixed reference,the ideal passage frequency. vpf = z f\u1d63 = z\u00b7rpm\/60 unequal spacing,multiple rows,slip or several rotors can require another event model; amplitude is not a standalone condition verdict. s12\"><details><summary><span><strong>Vane Pass Frequency<\/strong><small>VPF<\/small><\/span><span class=\"vr-state vr-math\">VERIFIED_ENGINEERING_IDENTITY<\/span><\/summary><div class=\"vr-term-body\"><p>For Z equally spaced vanes rotating at f\u1d63 past a fixed reference,the ideal passage frequency.<\/p><pre class=\"vr-formula\">VPF = Z f\u1d63 = Z\u00b7RPM\/60<\/pre><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Unequal spacing,multiple rows,slip or several rotors can require another event model; amplitude is not a standalone condition verdict.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S12\">S12<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"V\" data-category=\"Quantities\" data-search=\"velocity v quantities time derivative of displacement in the same coordinate and reference frame. v(t) = dx\/dt velocity rms is used in some applicable machine-evaluation procedures,but is not the universal primary parameter for every iso part or machine. s10 s12\"><details><summary><span><strong>Velocity<\/strong><small>v<\/small><\/span><span class=\"vr-state vr-math\">VERIFIED_ENGINEERING_IDENTITY<\/span><\/summary><div class=\"vr-term-body\"><p>Time derivative of displacement in the same coordinate and reference frame.<\/p><pre class=\"vr-formula\">v(t) = dx\/dt<\/pre><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Velocity RMS is used in some applicable machine-evaluation procedures,but is not the universal primary parameter for every ISO part or machine.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S10\">S10<\/a>, <a href=\"#source-S12\">S12<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"V\" data-category=\"Fundamentals\" data-search=\"vibration fundamentals variation of a mechanical quantity about a reference value,commonly described using displacement,velocity or acceleration versus time or frequency. quantity,reference,axis,descriptor,band and operating condition must accompany a useful record. s1\"><details><summary><span><strong>Vibration<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>Variation of a mechanical quantity about a reference value,commonly described using displacement,velocity or acceleration versus time or frequency.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Quantity,reference,axis,descriptor,band and operating condition must accompany a useful record.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S1\">S1<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"V\" data-category=\"Standards\" data-search=\"vibration severity standards an evaluation outcome obtained by applying stated criteria to a defined machine,measurement quantity,location,direction,band and operating condition. no universal a=new,b=acceptable,c=alert,d=danger mapping or numeric boundary is reproduced. use the exact applicable current standard part and licensed text. s6\"><details><summary><span><strong>Vibration Severity<\/strong><\/span><span class=\"vr-state vr-standard\">VERIFIED_OFFICIAL_STANDARD_RECORD<\/span><\/summary><div class=\"vr-term-body\"><p>An evaluation outcome obtained by applying stated criteria to a defined machine,measurement quantity,location,direction,band and operating condition.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> No universal A=new,B=acceptable,C=alert,D=danger mapping or numeric boundary is reproduced. Use the exact applicable current standard part and licensed text.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S6\">S6<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"W\" data-category=\"Signal processing\" data-search=\"waterfall plot signal processing a sequence of spectra displayed against time,speed or another ordering variable. axes,scales,normalization,window,record spacing and operating history are required for interpretation. s4\"><details><summary><span><strong>Waterfall Plot<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>A sequence of spectra displayed against time,speed or another ordering variable.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Axes,scales,normalization,window,record spacing and operating history are required for interpretation.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S4\">S4<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"W\" data-category=\"Wave mechanics\" data-search=\"wavelength \u03bb wave mechanics spatial period of a propagating wave. \u03bb = c\u209a\/f c\u209a is phase speed for the relevant wave mode and medium; the relation is not a machinery-vibration severity rule. s12\"><details><summary><span><strong>Wavelength<\/strong><small>\u03bb<\/small><\/span><span class=\"vr-state vr-math\">VERIFIED_ENGINEERING_IDENTITY<\/span><\/summary><div class=\"vr-term-body\"><p>Spatial period of a propagating wave.<\/p><pre class=\"vr-formula\">\u03bb = c\u209a\/f<\/pre><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> c\u209a is phase speed for the relevant wave mode and medium; the relation is not a machinery-vibration severity rule.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S12\">S12<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"W\" data-category=\"Rotordynamics\" data-search=\"whirl rotordynamics precessional or orbital motion of a rotor or shaft centre. forward and backward directions are defined relative to shaft rotation and the coordinate convention. state whether the orbit is relative or absolute and how it was filtered and compensated. s5\"><details><summary><span><strong>Whirl<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>Precessional or orbital motion of a rotor or shaft centre. Forward and backward directions are defined relative to shaft rotation and the coordinate convention.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> State whether the orbit is relative or absolute and how it was filtered and compensated.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S5\">S5<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"W\" data-category=\"Signal processing\" data-search=\"window function signal processing a weighting applied to a finite record before a transform to control spectral-leakage behaviour. use the correct name hann (not \u201channing\u201d). window choice trades amplitude,noise bandwidth and frequency separation; there is no universal general-purpose choice. s4\"><details><summary><span><strong>Window Function<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>A weighting applied to a finite record before a transform to control spectral-leakage behaviour.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Use the correct name Hann (not \u201cHanning\u201d). Window choice trades amplitude,noise bandwidth and frequency separation; there is no universal general-purpose choice.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S4\">S4<\/a><\/p><\/div><\/details><\/article>\n<article class=\"vr-term\" data-letter=\"Z\" data-category=\"Statistics\" data-search=\"zero-to-peak statistics excursion from a stated zero or mean reference to one stated extreme. specify polarity or maximum absolute convention. it is not automatically half peak-to-peak for an asymmetric or offset waveform. s10\"><details><summary><span><strong>Zero-to-Peak<\/strong><\/span><span class=\"vr-state vr-editorial\">REVIEWED_EDITORIAL<\/span><\/summary><div class=\"vr-term-body\"><p>Excursion from a stated zero or mean reference to one stated extreme.<\/p><p class=\"vr-scope\"><strong>Scope \/ caution:<\/strong> Specify polarity or maximum absolute convention. It is not automatically half peak-to-peak for an asymmetric or offset waveform.<\/p><p class=\"vr-source\"><strong>Sources:<\/strong> <a href=\"#source-S10\">S10<\/a><\/p><\/div><\/details><\/article><\/div><\/section>\n  <section class=\"vr-section\"><h2>How to read the status labels<\/h2><div class=\"vr-section-in\"><ul><li><strong>VERIFIED_ENGINEERING_IDENTITY:<\/strong> a displayed identity or explicitly scoped model was independently checked; it is not called an ISO formula.<\/li><li><strong>VERIFIED_MANUFACTURER_GUIDE:<\/strong> the bearing equations are supported by the official SKF full-text guide and retain their geometry assumptions.<\/li><li><strong>VERIFIED_OFFICIAL_STANDARD_RECORD:<\/strong> edition,status,replacement and public scope were checked on the standards body&#8217;s official page; closed clauses are not reproduced.<\/li><li><strong>REVIEWED_EDITORIAL:<\/strong> a plain-language explanation reviewed for scope and non-diagnostic wording; it is not a normative quotation.<\/li><\/ul><\/div><\/section>\n  <section class=\"vr-section\"><h2>Standard and source register<\/h2><div class=\"vr-section-in\"><div class=\"vr-table-wrap\"><table><thead><tr><th>ID<\/th><th>Source<\/th><th>Status checked 16 Jul 2026<\/th><th>Supports here<\/th><th>Does not support<\/th><\/tr><\/thead><tbody><tr id=\"source-S1\"><th>S1<\/th><td><a href=\"https:\/\/www.iso.org\/standard\/68734.html\" rel=\"noopener\" target=\"_blank\">ISO 2041:2018, Edition 4<\/a><\/td><td>Published; confirmed 2024; stage 90.93<\/td><td>Official record for the current mechanical-vibration, shock and condition-monitoring vocabulary.<\/td><td>Closed normative definitions are not reproduced.<\/td><\/tr>\n<tr id=\"source-S2\"><th>S2<\/th><td><a href=\"https:\/\/www.iso.org\/standard\/52256.html\" rel=\"noopener\" target=\"_blank\">ISO 13372:2012<\/a><\/td><td>Published; stage 90.93<\/td><td>Official record for condition-monitoring and diagnostics vocabulary.<\/td><td>Closed normative wording requires licensed text.<\/td><\/tr>\n<tr id=\"source-S3\"><th>S3<\/th><td><a href=\"https:\/\/www.iso.org\/standard\/21831.html\" rel=\"noopener\" target=\"_blank\">ISO 13373-1:2002, Edition 1<\/a><\/td><td>Published; confirmed 2024; stage 90.93<\/td><td>Public scope covers measurement methods, parameters, transducers, locations, attachment, operating conditions and signal conditioning.<\/td><td>Does not make generic glossary associations diagnostic rules.<\/td><\/tr>\n<tr id=\"source-S4\"><th>S4<\/th><td><a href=\"https:\/\/www.iso.org\/standard\/68128.html\" rel=\"noopener\" target=\"_blank\">ISO 13373-2:2016, Edition 2<\/a><\/td><td>Published; systematic review; stage 90.20<\/td><td>Public scope covers processing, analysis and presentation techniques in time and frequency domains.<\/td><td>Application-specific procedures and closed clauses are not reproduced.<\/td><\/tr>\n<tr id=\"source-S5\"><th>S5<\/th><td><a href=\"https:\/\/www.iso.org\/standard\/40840.html\" rel=\"noopener\" target=\"_blank\">ISO 13373-3:2015, Edition 1<\/a><\/td><td>Published; confirmed; stage 90.93<\/td><td>Official public record for general vibration-diagnosis procedures.<\/td><td>A symptom is not converted into a one-feature fault verdict.<\/td><\/tr>\n<tr id=\"source-S6\"><th>S6<\/th><td><a href=\"https:\/\/www.iso.org\/standard\/63180.html\" rel=\"noopener\" target=\"_blank\">ISO 20816-1:2016, Edition 1<\/a><\/td><td>Published; stage 90.92; ISO\/FDIS 20816-1 under development<\/td><td>General measurement\/evaluation framework and need to define quantities, methods and limitations.<\/td><td>No machine-specific zone or numeric boundary is reproduced.<\/td><\/tr>\n<tr id=\"source-S7\"><th>S7<\/th><td><a href=\"https:\/\/www.iso.org\/standard\/73726.html\" rel=\"noopener\" target=\"_blank\">ISO 21940-1:2019 and ISO 21940-11:2016 + Amd 1:2022<\/a><\/td><td>Part 1 published\/confirmed 2024; Part 11 published and under review<\/td><td>Current rotor-balancing introduction and rigid-rotor procedures\/tolerance scope.<\/td><td>No closed quality-grade table or tolerance is reproduced.<\/td><\/tr>\n<tr id=\"source-S8\"><th>S8<\/th><td><a href=\"https:\/\/www.iso.org\/standard\/42442.html\" rel=\"noopener\" target=\"_blank\">ISO 19499:2007<\/a><\/td><td>Withdrawn 2019; replaced by ISO 21940-1:2019<\/td><td>Evidence that the former balancing guide was not a vibration glossary and is no longer current.<\/td><td>Not used as a current technical basis.<\/td><\/tr>\n<tr id=\"source-S9\"><th>S9<\/th><td><a href=\"https:\/\/www.skf.com\/binaries\/pub12\/Images\/0901d1968024acef-CM5118-EN-Spectrum-Analysis_tcm_12-113997.pdf\" rel=\"noopener\" target=\"_blank\">SKF Spectrum Analysis, CM5118 EN, printed p. 18<\/a><\/td><td>Official manufacturer full text; relevant page visually checked<\/td><td>Bearing-frequency names, geometry variables and BPFO\/BPFI\/BSF\/FTF equations.<\/td><td>Frequency alignment is supporting evidence, not standalone fault proof.<\/td><\/tr>\n<tr id=\"source-S10\"><th>S10<\/th><td><a href=\"https:\/\/www.bksv.com\/media\/doc\/br0094.pdf\" rel=\"noopener\" target=\"_blank\">Br\u00fcel &amp; Kj\u00e6r, Measuring Vibration, br0094, printed pp. 5\u20137<\/a><\/td><td>Official manufacturer full-text primer; relevant pages visually checked<\/td><td>Amplitude descriptors and single-sine displacement\/velocity\/acceleration relationships.<\/td><td>Historical general discussion is not treated as a current universal ISO limit.<\/td><\/tr>\n<tr id=\"source-S11\"><th>S11<\/th><td><a href=\"https:\/\/www.bipm.org\/en\/si-brochure-9\" rel=\"noopener\" target=\"_blank\">BIPM SI Brochure, 9th edition, version 4.01, Appendix 1 p. 154<\/a><\/td><td>Current official SI brochure at audit date; June 2026<\/td><td>Conventional standard acceleration g\u2099 = 9.80665 m\/s\u00b2.<\/td><td>g\u2099 is not a severity class.<\/td><\/tr>\n<tr id=\"source-S12\"><th>S12<\/th><td>Displayed engineering identities and scoped model derivations<\/td><td>DERIVED \/ GENERAL ENGINEERING \u2014 not an ISO formula<\/td><td>Calculus identities, unit ratios and explicitly named SDOF or ideal kinematic models.<\/td><td>The model assumptions printed beside each equation are part of the formula.<\/td><\/tr><\/tbody><\/table><\/div><p class=\"vr-needs\"><strong>NEEDS_LICENSED_SOURCE:<\/strong> full normative texts of ISO 2041:2018, ISO 13372:2012, applicable ISO 20816 parts, ISO 21940 parts and ISO 13373 diagnostic procedures are not licensed in this audit record. No closed definition,clause,zone boundary,balance grade,tolerance or API 670 requirement is invented. ISO 19499:2007 is withdrawn and was a balancing guide\u2014not a vibration glossary; ISO 21940-1:2019 is its current replacement.<\/p><\/div><\/section>\n  <section class=\"vr-section\"><h2>Key corrections from the former page<\/h2><div class=\"vr-section-in\"><ul><li>Removed \u201cbased on ISO 19499\u201d: that 2007 document was a rotor-balancing guide,was withdrawn in 2019 and was replaced by ISO 21940-1:2019.<\/li><li>Removed universal 10\u20131000 Hz,crest-factor,kurtosis,oil-whirl,HFD and sensor-band thresholds.<\/li><li>Removed A=new\/B=acceptable\/C=alert\/D=danger language and every generic ISO severity implication.<\/li><li>Corrected base-excitation transmissibility by restoring the numerator and naming the SDOF model.<\/li><li>Changed deterministic fault statements to non-unique observations requiring corroboration.<\/li><li>Removed fixed proximity-probe sensitivity,blind runout subtraction and external font\/runtime dependencies.<\/li><\/ul><\/div><\/section>\n  <footer class=\"vr-section\"><div class=\"vr-section-in\">Scientific audit revision: 16 July 2026. English source page; translations follow only after the source is verified.<\/div><\/footer>\n<\/main>\n<script>\n(function(){'use strict';var root=document.getElementById('vbm-vref'),search=document.getElementById('vr-search'),category=document.getElementById('vr-category'),status=document.getElementById('vr-status'),items=Array.prototype.slice.call(root.querySelectorAll('.vr-term')),buttons=Array.prototype.slice.call(root.querySelectorAll('.vr-letter')),letter='';function apply(){var q=search.value.trim().toLowerCase(),cat=category.value,count=0;items.forEach(function(item){var show=(!q||item.getAttribute('data-search').indexOf(q)!==-1)&&(!cat||item.getAttribute('data-category')===cat)&&(!letter||item.getAttribute('data-letter')===letter);item.hidden=!show;if(show)count++});status.textContent=count===87&&!q&&!cat&&!letter?'Showing all 87 reviewed terms.':'Showing '+count+' of 87 reviewed terms.'}search.addEventListener('input',apply);category.addEventListener('change',apply);buttons.forEach(function(button){button.addEventListener('click',function(){letter=button.getAttribute('data-letter');buttons.forEach(function(other){other.setAttribute('aria-pressed',String(other===button))});apply()})});document.getElementById('vr-clear').addEventListener('click',function(){search.value='';category.value='';letter='';buttons.forEach(function(button){button.setAttribute('aria-pressed',String(button.getAttribute('data-letter')===''))});apply();search.focus()})})();\n<\/script>\n\n","protected":false},"excerpt":{"rendered":"<p>Review 87 vibration terms with explicit formula assumptions, source status and non-diagnostic cautions; no universal ISO alarms, fault verdicts or closed standard definitions.<\/p>","protected":false},"featured_media":0,"template":"","meta":{"ai_generated_summary":"","footnotes":""},"categories":[],"tags":[],"class_list":["post-100283","calculator","type-calculator","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/vibromera.eu\/el\/wp-json\/wp\/v2\/calculator\/100283","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/vibromera.eu\/el\/wp-json\/wp\/v2\/calculator"}],"about":[{"href":"https:\/\/vibromera.eu\/el\/wp-json\/wp\/v2\/types\/calculator"}],"version-history":[{"count":4,"href":"https:\/\/vibromera.eu\/el\/wp-json\/wp\/v2\/calculator\/100283\/revisions"}],"predecessor-version":[{"id":102630,"href":"https:\/\/vibromera.eu\/el\/wp-json\/wp\/v2\/calculator\/100283\/revisions\/102630"}],"wp:attachment":[{"href":"https:\/\/vibromera.eu\/el\/wp-json\/wp\/v2\/media?parent=100283"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/vibromera.eu\/el\/wp-json\/wp\/v2\/categories?post=100283"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/vibromera.eu\/el\/wp-json\/wp\/v2\/tags?post=100283"}],"curies":[{"name":"\u03b5\u03c1\u03b3\u03b1\u03c3\u03af\u03b1","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}