Traceable Dynamic Calibration of Force Transducers by Primary Means
Nicholas Vlajic, Akobuije Chijioke
We describe an apparatus for traceable, dynamic calibration of force transducers using harmonic excitation, and report calibration measurements of force transducers using this apparatus. In the apparatus, the force applied to the transducer is produced by the acceleration of an attached mass, and is determined according to Newton's second law, F = m a. The acceleration is measured by primary means, using laser interferometry. The capabilities of this system are demonstrated by performing dynamic calibrations of two shear-web-type force transducers up to a frequency of 2 kHz with an expanded uncertainty of 1.0 % or below. We give an accounting of all significant sources of uncertainty, including a detailed analysis of the effects of dynamic tilting (rocking), which has been identified as a leading source of uncertainty in such harmonic force calibration systems. We further present the application of a model of the transducer and calibration system to determine parameters describing the dynamic behavior of the transducer.