Pressure switch

A pressure switch is a device that operates an electrical contact when a preset fluid pressure is reached. The switch makes an electrical contact on either pressure rise or pressure fall from a certain preset pressure level. Pressure switches are in a wide range of industrial and residential applications like HVAC systems, well pumps, furnaces, etc.

A mechanical pressure switch uses a spring and a diaphragm, or piston, to control at what pressure the micro-switch is triggered. The spring is the opposing force to the inlet pressure and the spring's pretension is adjusted with a set screw or knob. The spring pretension directly correlates to the pressure at which the switch makes an electric contact. When the pressure drops, the switch resets to its original state.

An electronic pressure switch uses an electrical pressure sensor to measure the change in inlet pressure. They have digital displays to set up the switching function. The switch point can be manufacturer set or can be programmed on-site according to the application requirements. Switch point, output signals, hysteresis, delay time, etc. are some functions that can be adjusted by the user according to the requirements.