Sensor interface for multimodal evaluation of capacitive sensors

Abstract

Capacitive proximity sensing can be done in different modes. The single ended mode usually offers a higher signal to noise ratio (SNR) and-in conjunction with active guarding-high robustness. However, it can be blind for objects with low permittivity close to the sensor surface. The differential mode usually has a worse SNR but has the capability to detect objects in situations where the single ended mode is blind. Thus, we propose a measurement circuitry to combine both modes. It is compared to state of the art sensors and the benefits of this approach are demonstrated by means of experimental investigations. © 2013 Published under licence by IOP Publishing Ltd.