Electromechanical switches are simple, cheap, and widely available (Fig. 1). However, they’re also plagued with a number of disadvantages, including wear with repeated use, and the potential for arcing.
1. Capacitive switch technology brings many advantages, including the ability to operate in a sealed environment. (Source: TI: TIDA-00343: Low-Power Touch Through Glass Reference Design)
The last characteristic can be a serious problem in many industrial applications. In hazardous environments, for example, control switches may be part of explosion-proof controllers. These are housed in sealed metallic enclosures with thick glass windows to display local readout and programming functions. With traditional switch technology, the operator must open the enclosure to change a setting or touch a switch. This may call for special procedures and even require shutting down a process.