Comparison Protocol
International calibration standards specify the methods and instrumentation used for the primary calibration of vibration transducers. Applying the methods in ISO 16063-16 ensures that the phase and magnitude of sensor sensitivity are measured with high accuracy. This procedure compares the output of the sensor under test with a standard transducer on a shaker table.
The evaluation is valid across a wide frequency range determined by the shaker capabilities.
Sensor Mounting
Physical coupling between the reference transducer and the accelerometer under test affects the high-frequency response. According to ISO 16063-16, the mounting surfaces must be polished and flat to prevent unwanted mechanical resonances. Misalignment of the axes can introduce transverse sensitivity errors into the measurement.
Using a thin layer of grease or a specialized threaded stud ensures rigid coupling.
Uncertainty Calculation
Calculation of the measurement uncertainty requires accounting for multiple environmental and electrical sources of error. In the framework of ISO 16063-16, the uncertainty budget must include the drift of the reference sensor, the noise of the signal conditioner and the transverse motion of the vibration exciter. The standard requires that the total expanded uncertainty remains below specified limits for the calibration to be valid.
This systematic accounting of errors ensures that the calibration certificates are internationally recognized. Laboratories must participate in round-robin testing to verify their uncertainty claims.
Transduction Traceability
Traceability to primary standards is maintained through continuous calibrations of the reference accelerometer. Under ISO 16063-16, the reference is calibrated using laser interferometry. This link guarantees that the measurements trace back to fundamental units of length and time.
