How does a pressure switch operate?

• A. It detects pressure difference
• B. It changes color of housing
• C. When pressure reaches the setpoint it makes or breaks a contact
• D. It measures temperature

Answer: (C)

A pressure switch senses the pressure in a system and uses that signal to actuate electrical contacts when the pressure reaches a preset value. The sensing element, typically a diaphragm, bellows, or piston, deflects as pressure changes; that movement moves a linkage or lever that opens or closes the electrical contacts. The setpoint can be adjustable or fixed, and the switch can be normally open or normally closed, so it can either start or stop a circuit at the chosen pressure. This is what lets the device control equipment (like a pump or compressor) automatically based on pressure, rather than just indicating pressure or measuring temperature.