High resolution sigma delta modulator for capacitance sensor terminal displacement measurement

摘要

A single plate capacitance sensor includes a sensor capacitor and a reference capacitor that share common plate. A capacitance-to-digital sigma delta modulator provides separate sensor excitation and reference excitation signals to the sensor capacitor and the reference capacitor to provide high resolution detection. Programmable ratio-metric excitation voltages and adaptive excitation voltage sources can be used to enhance modulator performance.

主权项

1. A sensor circuit comprising:
a capacitance sensor that includes a sensor capacitor and a reference capacitor, a sensor plate terminal connected to the sensor capacitor, a reference plate terminal connected to the reference capacitor, and a common plate terminal connected to both the sensor capacitor and the reference capacitor, wherein spacing between the sensor plate terminal and the common plate terminal change in relation to a sensed parameter; and a capacitance-to-digital sigma delta modulator that includes an integrator having an input connected to the common plate terminal and an output, a quantizer connected to the output of the integrator that produces a pulse code modulated output signal, and an excitation signal generator that provides a sensor excitation signal to the sensor plate terminal and a reference excitation signal to the reference plate terminal.