Controlled engineering worksheet

Spectral Frequency Relationship Worksheet

Convert a measured frequency to shaft order and, when you have a documented reference, compare the two numerically. This page does not identify a fault from one peak.

RPM / Hz / CPM / orderSource-controlled referenceNo fault probability

Important diagnostic boundaryA spectral peak at an expected frequency may or may not represent the corresponding fault. Amplitude pattern, harmonics and sidebands, direction, phase, time waveform, operating condition, component geometry, history and other measurements must be considered. A numerical frequency match is not a diagnosis, severity rating, alarm or maintenance instruction.

1. Measurement record

Keep the arithmetic tied to the measurement and machine state that produced it.

Case or report ID

Asset or machine ID

Shaft, train and relevant components

Operating condition and capture time

Measurement quantity and processing

Sensor location and direction

2. Frequency relationship

No engineering values are prefilled. Use the speed measured for the same operating state as the spectrum.

Running speed (r/min)Strict decimal point or comma; no thousands separator or exponent.

Measured peak value

Measured peak unit

Optional comparison mode

Reference label (comparison modes)

Direct reference valueUsed only in direct-reference mode.

Direct reference unit

Integer teeth / blades / vanes countUsed only in count mode; must belong to the identified shaft.

Entered comparison tolerance (Hz)

Tolerance basis

Reference derivation and controlled source

Accountable analyst or procedure reference

3. Evidence gates

The arithmetic is available with incomplete gates, but no diagnostic conclusion is produced.

Speed is contemporaneous. The applicable shaft speed was measured or reliably recorded for this spectrum and its variation is understood. Components and kinematics are identified. Bearing designation/geometry, teeth, blades, ratios, belt data and adjacent sources are recorded as relevant. Measurement definition is adequate. Quantity, amplitude convention, bandwidth, processing, sensor location/direction, mounting and instrument state are documented. The spectrum pattern is reviewed. Fundamental, harmonics, sidebands, amplitudes, broadband content and nearby machinery are considered, not only one peak. History and comparable conditions are reviewed. Baseline, trend and prior readings at consistent load/speed are available or their absence is stated. Additional evidence is reviewed as applicable. Phase, time waveform, orbit, run-up/coast-down, current, envelope, oil, temperature or process evidence is considered. Reference frequency is independently verified. Geometry, shaft relation, source equation and frequency convention were checked outside this page. Diagnosis and action remain separate. Fault, severity, alarm, maintenance and shutdown decisions follow an approved process and competent review.

Ikke beregnet

Running frequency–

Measured peak–

Orden–

Nearest integer relationship–

Reference frequency–

Signed / absolute offset–

Relative difference–

Entered-tolerance comparison–

Evidence gates recorded–

Equations and classification

These are unit conversions and general arithmetic. They are not formulas issued by ISO and they do not encode a diagnostic rule.

f_r [Hz] = n [r/min] / 60

order = f_peak [Hz] / f_r [Hz]

count mode: f_ref [Hz] = z x f_r [Hz], where z is the documented integer count on this shaft

delta_f = f_peak – f_ref; relative difference = |delta_f| / f_ref x 100%

within entered tolerance only when |delta_f| <= T_entered

The equality rule is explicit: an offset exactly equal to the entered tolerance is reported as within that tolerance. The tolerance is not generated by ISO, SKF or this page; it must be justified for the acquisition and speed variability.

A frequency relationship is not a fault identifierEven an exact numerical match does not prove the origin of the peak, the presence of damage, its root cause, severity, remaining life or required action. Conversely, a mismatch does not exclude a fault when speed variation, slip, geometry, resolution, modulation or measurement limitations have not been resolved.

Verified sources and evidence boundary

ID	Kilde	Verified public/full-text support	What this worksheet does not infer
S1	BIPM, SI Brochure, 9th edition, version 4.01 (June 2026)	The current SI brochure defines minute in relation to the second (1 min = 60 s); hertz is the SI unit s^-1.	The RPM-to-Hz conversion is dimensional arithmetic, not an ISO vibration-diagnostic formula.
S2	SKF, Spectrum Analysis – The key features of analyzing spectra, CM5118 EN, pp. 4-6	SKF requires machine/component identification, applicable running speed, measurement type/location, history, spectral context and multi-parameter monitoring; it states that peaks at identified fault frequencies may or may not represent the indicated fault.	No single-peak probability, source ranking, severity or action is produced.
S3	SKF CM5118 EN, pp. 9-16	The worked diagnostic guidance uses amplitude ratios, planes, multiple harmonics and phase; it notes that a bent-shaft signature may look identical to misalignment until phase is considered.	1x, 2x, 3x or 0.5x alone is not labelled unbalance, misalignment, looseness, rub or bent shaft.
S4	SKF CM5118 EN, pp. 18 and 23	Bearing defect calculations require rolling-element count, diameters and contact angle; gear mesh is teeth count times the speed of the shaft carrying that gear.	Any peak above 5x/10x is not automatically a bearing or gear fault; one count is not silently treated as both blades and gear teeth.
S5	ISO 13373-1:2002, Edition 1	Published and confirmed in 2024. Its public scope covers general vibration measurement and data-collection procedures, parameters, transducers, locations, attachment, operating conditions and signal conditioning.	The public record does not validate universal fault-frequency scores or the former web actions. Full normative detail is NEEDS_LICENSED_SOURCE.
S6	ISO 13373-2:2016, Edition 2	Published; under systematic review at the audit date. Its public scope covers processing, presentation and time/frequency-domain analysis, with application-specific and refined diagnostic techniques.	The abstract does not define fixed +/-order tolerances, one-peak probabilities or universal fault actions.
S7	ISO 13373-3:2015, Edition 1	Published and confirmed. The public scope describes a practical structured approach to rotating-machine vibration diagnosis and examples of common faults.	This page does not claim to implement the protected diagnostic procedure. Clause-level requirements are NEEDS_LICENSED_SOURCE.
S8	ISO 20816-1:2016, Edition 1	Published at stage 90.92. Its public scope concerns defined vibration measurements, magnitude and change, operational monitoring, acceptance and operational-limit guidance; ISO lists an expected replacement.	It does not make one frequency order a fault probability. No ISO 20816 limit is embedded here.
S9	ISO/FDIS 20816-1, Edition 2	Under development in the approval phase at stage 50.00; intended to replace ISO 20816-1:2016.	It is not yet a published replacement and is not used as a current diagnostic or numerical criterion.
S10	ISO 10816-1:1995, Edition 1	Withdrawn in 2016 and revised by ISO 20816-1:2016.	It is historical, not an interchangeable current citation and not proof of a fault-source table.

NEEDS_LICENSED_SOURCENo clause, diagnostic decision tree, protected table, tolerance or severity rule is guessed from an ISO abstract. Applying ISO 13373 or machine-specific ISO 20816 criteria requires the legally available complete applicable document, amendments and competent review.

Corrections made in this audit

The fabricated “most likely source” and probability ranking were removed

The old code assigned HIGH/MEDIUM/LOW labels from a single order using undocumented scores. It had no amplitude, phase, direction, trend, uncertainty or machine-specific likelihood model.

Hidden universal matching tolerances were removed

The former +/-0.05, +/-0.08 and expanded three-times tolerances, the greater-than-5x high-frequency rule and fixed +/-3 Hz electrical window had no stated acquisition or source basis. Comparison now requires a user-entered tolerance and its basis.

Bearing, gear and blade relationships are no longer conflated

A high order alone is not a bearing defect or gear problem. Direct bearing references require verified bearing geometry or manufacturer data; count mode is only the transparent z times identified-shaft relationship.

Unsafe diagnostic and maintenance commands were removed

The former output could recommend balancing, immediate alignment, load change, oil change, bearing replacement or an emergency response from one frequency. This worksheet generates none of those decisions.

Withdrawn ISO 10816 and current ISO 20816 are separated

ISO 10816-1:1995 is withdrawn. ISO 20816-1:2016 remains published but is scheduled for revision; neither public record supports a universal frequency-to-fault lookup.

Input handling and traceability were rebuilt

No defaults, presets, automatic calculation, local history, clipboard diagnosis, URL persistence or dynamic HTML are used. Decimal point and comma are supported under a strict grammar; mixed separators, exponents, non-finite values and invalid ranges are rejected, and changed inputs make prior results stale.