Dynamic Matching of Acceleration Transducers

Small mismatches between similarly manufactured accelerometers stem from slight differences between their flexural elements, seismic masses and their mountings, as well as variations in damping ratios. This is not detrimental for measuring absolute accelerations, but when it is desired to measure differential accelerations, very large errors may result. This is probably the main reason why transducers for measuring differential acceleration are not generally commercially available. Measuring the differential acceleration between two accelerometers mounted in different locations of an item provides a convenient means of measuring the relative velocity and displacement by single and double integration of the differential acceleration signal. To do this with good accuracy both accelerometers must have identical static and dynamic response characteristics. A method of matching the D.C. and dynamic response characteristics of any number of similarly manufactured piezoresistive acceleration transducers is described. This method is based on electronic compensation networks whereby the combined transfer functions of the transducers and their compensation networks are matched, enabling differential acceleration measurements with good accuracy. In addition to matching the effective transfer functions of the transducers, this method also significantly extends the operating frequency range in both absolute and differential measurements. The line taken is based on a general mathematical model, which was developed for quantifying error sources in differential measurements at large.