What is vibration phase angle?

Phase angle describes the timing relationship between a vibration signal and a reference. It is measured in degrees (0–360°) and indicates where in the rotation cycle the peak vibration occurs. Phase is critical for balancing and diagnosing machine faults.

How do I measure phase angle?

Phase is measured using a tachometer (keyphasor) as a reference, combined with a vibration sensor. The phase angle is the angular difference between the tachometer pulse and the peak of the 1× vibration signal.

What is the vector sum of two vibration signals?

The vector sum combines two vibration signals (each with amplitude and phase) into a single resultant vector. It uses the formula: add the x-components and y-components separately, then calculate the resultant amplitude and phase.

Why is relative phase important in balancing?

In single-plane balancing, the phase shift between the original vibration and the trial-weight run indicates the angular correction needed. A 180° phase shift means the correction weight should be placed opposite to the trial weight.

What does 0° vs 180° phase mean?

0° phase between two measurement points means the points move in the same direction simultaneously (in-phase, common with unbalance). 180° means they move in opposite directions (out-of-phase, typical of misalignment or a rotor operating above its critical speed).

Free Engineering Tool — #018

Vibration Phase Angle Calculator

Calculate relative phase, vector sum, and vector difference of two vibration signals. Enter amplitude and phase for each signal.

Vector SumVector DifferenceRelative Phase

Results

Relative Phase Angle

—

Vector Sum (Amplitude)

—

Vector Sum (Phase)

—

Vector Difference (Amplitude)

—

Vector Difference (Phase)

—

Vector Representation

Each vibration signal is a vector V = A∠φ, with Cartesian components:

Vector Sum & Difference

Relative Phase

The relative phase angle between two signals:

Practical Example

Example — Balancing Run Comparison

Signal 1: 5.2 ∠45° → x₁ = 3.677, y₁ = 3.677

Signal 2: 3.8 ∠200° → x₂ = −3.571, y₂ = −1.300

Vector difference: Δx = 7.248, Δy = 4.977 → |ΔV| = 8.79 ∠34.4°

Relative phase: |200° − 45°| = 155°

ℹ️ Tip: In single-plane balancing, the vector difference between the original run and the trial-weight run represents the effect of the trial weight alone.