Glossary · Pneumatics and hydraulics
Pressure switch
Also known as: Pressure sensor switch
German: Druckschalter
In fluid power and process automation, a pressure switch is a device that changes the state of an electrical contact or output when the pressure of a fluid reaches a set value, often with adjustable switching point and hysteresis.
- Fluid power
In one sentence
A pressure switch changes an electrical output when fluid pressure reaches a set point, often with adjustable hysteresis.
Example
A pressure switch at the machine inlet signals the PLC when supply pressure drops below 5 bar, and the machine stops at the end of the cycle.
How it applies
- Engineering: Pressure switches monitor supply pressure, filter clogging or clamping pressure. Electronic versions with displays and IO-Link are replacing mechanical switches.
- Commissioning: Switching points and hysteresis are set and recorded.
- Operation: Alarm messages from pressure switches tell the operator what to check.
- Documentation: Write alarm texts that name the cause and the check ("Supply pressure below 5 bar: check compressed air supply and FRL unit"). If a pressure switch is part of a safety function, describe that function and its validation separately from standard monitoring.
Pressure switch vs. pressure transmitter
A pressure switch gives a binary signal at a set point. A pressure transmitter gives a continuous measurement, for example 4–20 mA, from which the controller derives limits.