CAPACITIVE LIQUID LEVEL MEASUREMENT WITH DIFFERENTIAL OUT-OF-PHASE CHANNEL DRIVE TO COUNTERACT HUMAN BODY CAPACITANCE

摘要

In described examples, capacitive liquid level measurement uses differential out-of-phase (OoP) channel drive to counteract human body capacitance. A container assembly (10) includes a capacitive sensor (20) with symmetrical CHx and CHy capacitor electrodes (21x, 21y), corresponding in height to a liquid level measurement range. A CHx driver provides a CHx excitation/drive to the CHx electrode (21x), and a CHy driver provides OoP CHy excitation/drive to the CHy electrode (21y) that is substantially 180 degrees out-of-phase with the CHx drive. Capacitance associated with the liquid level (13) is measured by acquiring capacitance measurements through the CHx channel (such as based on capacitive charge transfer), and converting the capacitance measurements to an analog voltage corresponding to liquid-level capacitance (which can then be converted to digital data). The capacitive sensor can be configured with SHLDx/SHLDy shields (23x, 23y) disposed behind, and driven in phase with, respective CHx/CHy electrodes (21x, 21y).