How does a pressure switch work?
Function description for normally open (NO): Pressure is applied to the diaphragm / pistons through the pressure connector. If the generated pressure force is greater than the pre-tensioned force of the pressure spring, the plunger moves towards the counter-contact, carrying along the contact disc, and closes the circuit. The switch opens again when the pressure is reduced by the hysteresis value. Function description for normally closed (NC): Engaging happens in the reverse order. The adjustment screw enables the switching point to be changed within the adjustment range.
The micro switch of a change-over contact system (snap-action) offers both, a NC and a NO contact. The swivel contact is activated by the plunger. The circuit is closed by the NC as long as no pressure is applied. When the applied pressure exceeds the set switching point, the swivel contact changes over and closes the circuit via the NO.