Frequency Domain
Metrological verification establishes the performance envelope of electrodynamic shaker calibration by subjecting the armature to controlled sinusoidal sweeps across a specified acceleration spectrum. Accelerometer standards mounted on the slip table compare voltage outputs against known reference transducers to quantify frequency response anomalies. Harmonic distortion accumulates in the magnetic coil circuit as thermal dissipation alters copper wire resistance during protracted sweeps.
Resonant peaks within the fixture mounting assembly introduce systematic errors if mass loading exceeds the static overturning moment specified by the armature manufacturer.
Traceable Uncertainty
Transducer sensitivity coefficients derive from laser interferometry primary standards maintained by national measurement institutes. Secondary reference accelerometers transfer this traceability down the calibration chain to the field accelerometer arrays bolted onto the vibration table. Phase lag measurements between the reference signal and the device under test require high sampling rates to resolve timing jitter within the digital signal processor.
Random errors arising from thermal noise in the charge amplifier contribute to the combined standard uncertainty reported in the calibration certificate.
Transverse Motion
Off-axis cross-talk evaluation verifies the directional restraint of the armature guidance bearings during high-g testing. Radial velocity components degrade the purity of the linear motion by introducing parasitic bending moments into the test specimen. Laser vibrometers measure lateral displacement at multiple points across the shaker head to isolate cross-axis acceleration ratios from the primary vector.
Bearing wear increases mechanical clearance over operational hours and raises transverse motion beyond the tolerance limits defined in ISO standards.
Armature Resonance
Structural integrity checks identify high-frequency modal frequencies where the shaker table deforms rather than moves as a rigid body. Modal analysis reveals nodal lines across the magnesium or beryllium armature surface during swept sine excitation. Damping material degradation inside the cooling blower housing changes the acoustic noise floor and alters the low-frequency background acceleration profile.
Transducer mounting torque relaxation during high acceleration testing shifts the local resonance frequency of the sensor installation and invalidates the upper bound of the usable frequency range.
