1 Introduction

Proximity detection applications that use capacitive sensing have common system challenges which include sensitivity, responsiveness, and power. For example, high sensitivity and a large sensing range are related to the sensor size (SNOA940). A larger sensor size achieves higher sensitivity but more external noise couples into the system, which degrades the signal-to-noise ratio (SNR). An SNR of 6 dB or more produces solid results when processed with the proper algorithms. These tradeoffs are examined in more detail further in this application note. In end-equipment such as automotive applications, white goods, and personal electronics, the capacitive measurements can be affected by whether or not there are nearby grounded objects adjacent to the device. In the following sections this phenomenon, referred to as a ground shift, is further illustrated under the testing conditions that use various ground configurations. These ground configurations are summarized in the following analytical models.