{"id":192,"date":"2025-10-31T00:25:51","date_gmt":"2025-10-31T00:25:51","guid":{"rendered":"https:\/\/vibromera.eu\/glossary\/phase\/"},"modified":"2026-05-23T22:37:52","modified_gmt":"2026-05-23T22:37:52","slug":"phase","status":"publish","type":"glossary","link":"https:\/\/vibromera.eu\/yo\/glossary\/phase\/","title":{"rendered":"What is Phase in Vibration Analysis?"},"content":{"rendered":"

Understanding Phase in Vibration Analysis<\/h1>\n\t\t
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\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\tPortable balancer & Vibration analyzer Balanset-1A<\/a>\n\n\t\t\t\t\t\t\t\t<\/h4>\n\n\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t
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€<\/span>1,975.00<\/span> + VAT (if applicable)<\/h4><\/div>\n\t\t\t\t\t\t\t\t\t
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\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\tVibration sensor<\/a>\n\n\t\t\t\t\t\t\t\t<\/h4>\n\n\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t
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€<\/span>90.00<\/span> + VAT (if applicable)<\/h4><\/div>\n\t\t\t\t\t\t\t\t\t
\n\t\t\t\t\t\t\t\t\t\t<\/i><\/a>\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/a>Add to cart<\/a>\t\n\t\t\t<\/span>\n\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t\t\t
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\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\tOptical Sensor (Laser Tachometer)<\/a>\n\n\t\t\t\t\t\t\t\t<\/h4>\n\n\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t
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€<\/span>124.00<\/span> + VAT (if applicable)<\/h4><\/div>\n\t\t\t\t\t\t\t\t\t
\n\t\t\t\t\t\t\t\t\t\t<\/i><\/a>\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/a>Add to cart<\/a>\t\n\t\t\t<\/span>\n\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t\t\t
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€<\/span>6,803.00<\/span> + VAT (if applicable)<\/h4><\/div>\n\t\t\t\t\t\t\t\t\t
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\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\tReflective tape<\/a>\n\n\t\t\t\t\t\t\t\t<\/h4>\n\n\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t
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€<\/span>10.00<\/span> + VAT (if applicable)<\/h4><\/div>\n\t\t\t\t\t\t\t\t\t
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\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\tDynamic balancer \u201cBalanset-1A\u201d OEM<\/a>\n\n\t\t\t\t\t\t\t\t<\/h4>\n\n\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t
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€<\/span>1,735.00<\/span> + VAT (if applicable)<\/h4><\/div>\n\t\t\t\t\t\t\t\t\t
\n\t\t\t\t\t\t\t\t\t\t<\/i><\/a>\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/a>Add to cart<\/a>\t\n\t\t\t<\/span>\n\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/section>\n\t\t\n

Phase<\/strong> describes the timing relationship between two signals or, more usefully in rotating-machinery work, the timing of a vibration<\/a> signal relative to a fixed reference mark on the rotating shaft. It answers the question of where<\/em> in the rotation the vibration is happening, and it is normally measured in degrees from 0\u00b0 to 360\u00b0, one full revolution of the shaft. If amplitude<\/a> tells you how much<\/em> a machine is vibrating and frequency<\/a> tells you how fast<\/em>, phase tells you how it is moving<\/em> \u2014 which is precisely what separates faults that share the same frequency.<\/p>\n

That last point is the heart of why phase matters. Unbalance<\/a>, misalignment<\/a>, a bent shaft<\/a> and looseness<\/a> can all raise the 1\u00d7 running-speed<\/a> peak; phase is often the only way to tell them apart without dismantling the machine.<\/p>\n

1. How Phase Is Measured<\/h2>\n

Two signals are needed to read phase:<\/p>\n

    \n
  1. A vibration signal<\/strong> \u2014 the primary measurement from an accelerometer<\/a> or proximity probe<\/a> watching the machine’s motion.<\/li>\n
  2. A reference signal<\/strong> \u2014 a once-per-revolution timing pulse from a tachometer<\/a>, aimed at a strip of reflective tape<\/a> or a keyway so that it fires a clean pulse each time the mark passes the sensor. Functionally this is the same role played by a permanently installed Keyphasor<\/a>.<\/li>\n<\/ol>\n

    The vibration analyser<\/a> then measures the time delay between the reference pulse and the first positive peak of the vibration signal at a chosen frequency \u2014 usually 1\u00d7 running speed \u2014 and converts that delay into an angle. A reading of 90\u00b0, for instance, means the vibration peak arrives one-quarter of a revolution after the reference mark passes the tachometer. Because the result is tied to a specific frequency, phase is most often quoted alongside the 1\u00d7 component; the same idea, generalised across the spectrum, is what makes the phase angle<\/a> a building block of plots such as the Bode<\/a> and Nyquist<\/a> diagrams.<\/p>\n

    2. The Diagnostic Power of Phase<\/h2>\n

    Phase is far more than a number. By comparing readings taken at different points on a machine, in the same measurement direction, an analyst can confirm or eliminate specific diagnoses with high confidence. The recurring theme is the comparison of two locations: if they move together<\/em> the picture points one way; if they move in opposition<\/em> it points to another. The sub-sections below cover the classic patterns.<\/p>\n

    Confirming unbalance<\/h3>\n

    Pure unbalance gives similar phase readings \u2014 typically within about \u00b130\u00b0 \u2014 when measured in the same radial direction (say, horizontal) at both bearings of a rotor. The whole rotor is being pulled in one direction at one instant by the heavy spot, so the two ends march in step. Comparing horizontal and vertical readings at one bearing adds another clue: genuine unbalance tends to show a roughly 90\u00b0 difference between them.<\/p>\n

    Diagnosing misalignment<\/h3>\n

    Phase is one of the most definitive ways to confirm shaft misalignment<\/a>. Take axial phase readings on either side of a coupling<\/a>: a 180\u00b0 phase shift (\u00b130\u00b0) across it is the textbook signature of angular misalignment, showing that as one shaft moves axially out, the other moves in \u2014 a pivoting, see-saw motion at the coupling.<\/p>\n

    Distinguishing unbalance from a bent shaft<\/h3>\n

    Both unbalance and a bent shaft<\/a> raise 1\u00d7 vibration, yet phase tells them apart. Axial phase readings taken at the two ends of the same motor or pump shaft that differ by about 180\u00b0 indicate a bow: the ends move in opposite axial directions as the bend rotates.<\/p>\n

    Identifying looseness or a cracked foundation<\/h3>\n

    When phase readings are erratic, unstable or non-repeatable, mechanical looseness<\/a> is the usual suspect. A marked change in phase as the probe is moved from a machine foot to its baseplate, or from the baseplate to the foundation, points to a loose anchor bolt or a cracked foundation \u2014 and hints at inadequate foundation stiffness<\/a>.<\/p>\n

    Confirming resonance<\/h3>\n

    As a machine runs up or coasts through a critical speed<\/a>, the 1\u00d7 phase makes a characteristic 90\u00b0 shift exactly at the resonance<\/a> peak and a full 180\u00b0 shift across the whole resonance region. Watching for that swing \u2014 easily captured during a coastdown<\/a> \u2014 is a definitive way to confirm a resonance rather than a forcing problem.<\/p>\n

    3. A Quick Reference for Phase Patterns<\/h2>\n\n\n\n\n\n\n\n
    Observation<\/th>\nLikely diagnosis<\/th>\n<\/tr>\n
    Both bearings in phase, same radial direction<\/td>\nUnbalance<\/td>\n<\/tr>\n
    \u2248180\u00b0 across the coupling, axial<\/td>\nAngular misalignment<\/td>\n<\/tr>\n
    \u2248180\u00b0 across the two ends of one shaft, axial<\/td>\nBent \/ bowed shaft<\/td>\n<\/tr>\n
    Erratic, non-repeatable phase<\/td>\nMechanical looseness<\/td>\n<\/tr>\n
    90\u00b0 shift at peak, 180\u00b0 through the region<\/td>\nResonance \/ critical speed<\/td>\n<\/tr>\n<\/table>\n

    These rules are guides, not guarantees: confirm with amplitude, spectrum shape and harmonic<\/a> content before committing to a repair.<\/p>\n

    4. Phase as the Key to Balancing<\/h2>\n

    Phase is indispensable for rotor balancing<\/a>. The 1\u00d7 phase reading points directly to the angular location of the heavy spot relative to the reference mark, telling the technician exactly where to add or remove a correction weight<\/a>. In practice the analyser records amplitude and phase before a trial weight<\/a> is fitted, again afterwards, and uses the change to compute the influence coefficients<\/a> that yield the final correction. A portable two-channel instrument such as the Balanset-1A<\/a> performs this amplitude-and-phase measurement in the machine’s own bearings at operating speed, then verifies the residual unbalance<\/a> once the weights are in place. For working out the angular split when a correction must be shared between weights, our Vibration Phase Angle Calculator<\/a> handles the vector geometry.<\/p>\n

    5. Why Phase Completes the Picture<\/h2>\n

    Without phase, a vibration analyst sees only part of the story \u2014 magnitudes and frequencies, but no sense of how the structure actually deforms through each turn. Phase supplies that missing context, converting a list of peaks into a clear statement of motion and lifting diagnostic confidence dramatically. It is the difference between knowing that a machine vibrates and knowing why. For that reason, phase belongs in every serious diagnosis and is the non-negotiable foundation of field balancing<\/a>.<\/p>\n

    \n

    \u2190 Back to Main Index<\/a><\/p>","protected":false},"excerpt":{"rendered":"

    A guide to phase analysis in vibration monitoring. Learn what phase is, how it is measured using a tachometer, and its critical role in diagnosing faults like unbalance and misalignment.<\/p>","protected":false},"featured_media":0,"template":"","meta":{"ai_generated_summary":"","footnotes":""},"categories":[114,109],"tags":[],"class_list":["post-192","glossary","type-glossary","status-publish","hentry","category-analysis","category-glossary"],"_links":{"self":[{"href":"https:\/\/vibromera.eu\/yo\/wp-json\/wp\/v2\/glossary\/192","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/vibromera.eu\/yo\/wp-json\/wp\/v2\/glossary"}],"about":[{"href":"https:\/\/vibromera.eu\/yo\/wp-json\/wp\/v2\/types\/glossary"}],"version-history":[{"count":1,"href":"https:\/\/vibromera.eu\/yo\/wp-json\/wp\/v2\/glossary\/192\/revisions"}],"predecessor-version":[{"id":101296,"href":"https:\/\/vibromera.eu\/yo\/wp-json\/wp\/v2\/glossary\/192\/revisions\/101296"}],"wp:attachment":[{"href":"https:\/\/vibromera.eu\/yo\/wp-json\/wp\/v2\/media?parent=192"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/vibromera.eu\/yo\/wp-json\/wp\/v2\/categories?post=192"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/vibromera.eu\/yo\/wp-json\/wp\/v2\/tags?post=192"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}