Differential Capacitive Transducers

Transducers with greater sensitivity and immunity to changes in other variables can be obtained by way of differential design, much like the concept behind the LVDT (Linear Variable Differential Transformer). Here’s the design of the differential capacitive transducer circuit;

Capacitive transducers provide relatively small capacitances for a measurement circuit to operate with, typically in the picofarad range. Because of this, high power supply frequencies (in the megahertz range!) are usually required to reduce these capacitive reactance to reasonable levels. Given the small capacitances provided by typical capacitive transducers, stray capacitances have the potential of being major sources of measurement error.