Microchip Technology Incorporated
Dual Polarity Mutual Capacitive Liquid Sensing

Abstract:

A level sensing controller includes a signal generator circuit to generate an excitation signal. The controller also includes a connection to route an inverse of the excitation signal to a first polar electrode of a first capacitor. The first polar electrode is coupled to a container to hold liquid. The controller also includes a connection to route the excitation signal to a second polar electrode of a second capacitor. The second positive polar electrode is coupled to the container. The controller also includes a connection to a sense electrode to form the first capacitor with the first polar electrode and to form the second capacitor with the second polar electrode. The controller also includes a measurement circuit configured to measure charge at sensing electrode and determine, based on the measured charge, whether a liquid in the container has reached a level of the second polar electrode.