Drives and Controls Magazine

Capacitive switch resists water, dirt and EMC

01 September, 1999

Capacitive switch resists water, dirt and EMC

Capacitive proximity switches have traditionally been vulnerable to the effects of water, dirt and electromagnetic interference, which can adversely affect their performance.

Now, the electrical equipment manufacturer Shurter claims to have overcome these limitations by developing a capacitive switch which adapts to changes in its environment. This ability allows the switch to be used in extreme climates and in tough industrial environments, as well as in areas where vandalism is a problem.

Electronic circuitry in the switch registers the slow changes in performance caused, for example, by an accumulation of dirt particles and water drops, and compensates for these changes.

This ability allows users to exploit the attractions of capacitive switches in applications where they would previously have been considered unsuitable. One of their attractions is that they do not have any vulnerable mechanical parts to fail through damage or wear and tear. In addition, the switches do not suffer from problems of pinched or sticking keys or loose actuators, and their lifetime is said to be many times longer than that of mechanical systems. Finally, because the actuation occurs without pressure, vibrations or strokes do not influence the switches` operation.

Shurter is producing its capacitive switches in three versions: momentary switch; defined pulse; and latching switch. Potential applications include traffic systems, lifts, vending machines, automated ticket machines, money machines, and public information terminals.