On-Off Controller
On-Off Controller
a regulator whose controlling member, upon receiving a signal from a sensor, can only move into one of two extreme positions—on or off. The flow of energy or material to the controlled object may be only maximal or minimal.
The simplest kind of on-off control mechanism is an electromagnetic relay, whose contacts are either open or closed, depending on the signal received from the sensor. On-off controllers are widely used in cases where the operation of equipment requires some control within given limits but does not require a high accuracy of control (for example, the control of electric furnaces, refrigerators, or steam heating and water heating).