SAR — Snap Acting Relay
The Snap Acting Relay (model SAR) is narrow-band pneumatic controller with an adjustable setpoint.
Pressure in the input chamber opposes the load on the adjusting spring. Whenever this input pressure exceeds the spring setting, the input signal seat will be closed and the open supply seat will allow full supply pressure to pass directly to the output. Conversely, whenever the input pressure is below the spring setting, the supply seat will be closed and the signal seat will be open. The output, in this case, will be equal to the signal.
Generally used for input signal of pneumatic controlled positioner.
