How to Calibrate a Vibration Meter

mechanical

Vibration meters measure acceleration, velocity, and displacement of machine vibrations for predictive maintenance and condition monitoring. Calibration verifies sensor sensitivity and frequency response using a reference vibration exciter. Accurate vibration measurement is essential for detecting bearing failures, imbalance, and misalignment before catastrophic equipment damage occurs.

Required Reference Standards

  • ISO 16063-21 - Vibration calibration by comparison
  • ISO 5348 - Accelerometer mounting
  • Reference vibration exciter with calibrated accelerometer

Calibration Procedure

  1. 1

    Visual and Connector Inspection

    Inspect the accelerometer sensor for damage, cable integrity, and connector condition. Verify the meter display functions correctly, battery is adequate, and all measurement modes (acceleration, velocity, displacement) are selectable.

  2. 2

    Sensor Mounting on Exciter

    Mount the accelerometer on the reference vibration exciter alongside the reference accelerometer using appropriate mounting method (stud, wax, or magnetic). Ensure both sensors are securely attached with consistent coupling.

  3. 3

    Sensitivity Verification at Reference Frequency

    Apply a known vibration level at the reference frequency (typically 159.2 Hz for 1000 rad/s) and compare the meter reading to the reference accelerometer output. This verifies the basic sensitivity (mV/g or mV/ms²).

  4. 4

    Frequency Response Check

    Test at a minimum of five frequencies spanning the meter's specified bandwidth (e.g., 10 Hz, 100 Hz, 1 kHz, 5 kHz, 10 kHz). Record the meter reading and reference value at each frequency to verify flat frequency response.

  5. 5

    Multi-Level Amplitude Check

    At the reference frequency, verify linearity by testing at three vibration levels (low, mid, high) within the measurement range. Calculate the sensitivity error at each level.

  6. 6

    Documentation

    Record all data including sensitivity values, frequency response deviations, and amplitude linearity. Issue the calibration certificate with measurement uncertainty and apply the calibration label.

Acceptance Criteria

Sensitivity error at the reference frequency must not exceed ±5% of the stated value. Frequency response must be within ±1 dB across the specified bandwidth. Amplitude linearity must be within ±3% across the measurement range.

Typical Calibration Interval

12 months

FAQ

Why is 159.2 Hz used as the reference calibration frequency?

The frequency 159.2 Hz corresponds to 1000 rad/s angular frequency, which simplifies the mathematical relationship between acceleration, velocity, and displacement. At this frequency, 1 g of acceleration equals approximately 9.81 m/s² and the velocity and displacement values are convenient round numbers.

How does mounting method affect vibration measurement accuracy?

The mounting method determines the usable frequency range. Stud mounting provides the widest bandwidth (up to the sensor's resonance). Adhesive and magnetic mounts reduce the effective bandwidth due to compliance in the mounting interface. Calibration should use the same mounting method as field measurements.

Can I field-verify a vibration meter without a calibration lab?

Portable vibration calibrators (hand-held exciters providing a known vibration level at a reference frequency) enable field verification of vibration meters. This checks basic sensitivity but not full frequency response. A full laboratory calibration is still required at the specified interval.

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