Devices that close or open electrical contacts in the event of pressure load (DIN ISO 1219-1). They are generally used if an electrical switching command or status signal should be issued when a set (pre-selected) pressure value is reached and exceeded, to trigger an immediately following work cycle (actuation of an electromagnetic directional valve) or to end a cycle sequence (deactivation of the pump motor, neutral position of an electromagnetic directional valve).
They are responsible for:
- Signalling specific pressure values,
- Initiating control and regulation processes.
Pressure switches can contain pistons, diaphragms or corrugated tubes as the pressure transmitting element. Although the two latter elements are absolutely free of leaks, they are only suitable for low pressures. Piston switches can also be designed for high pressures, but due to the sealing friction they have a hysteresis .
Schematic diagram of a pressure switch
In the case of an electro-mechanical pressure switch, a moving, sealed piston actuates an electrical switch. An electronic pressure switch operates according to the principle of strain gauges, which are switched in a full bridge. The sensor elements are mostly applied on a welded stainless steel diaphragm, are produced using thick-film technology (screen-printing process) and are temperature-compensated. The adjustment and evaluation of the measuring signal is mostly carried out by analogue electronics.