Pneumatic Sensors and Switches

Pressure switches monitor or control pressure in a pneumatic system. The category covers mechanical and electronic pressure switches, vacuum switches and differential-pressure switches that operate an electrical contact when a set value is reached.

A mechanical pressure switch converts a pressure measurement into movement of an electrical contact, such as a microswitch, without requiring its own power supply. An electronic pressure switch measures through a pressure sensor, requires power and may display the current pressure.

Pressure switches are used for pressure monitoring and control in systems, pressure vessels and pipework. They can monitor an upper or lower limit and often form part of a safety measure. Versions with a safety diaphragm or a manual-reset limiter are available for steam and hot-water boilers.

First choose between pressure, vacuum or differential pressure and define the required switching point. Check the setting range, fixed or adjustable switching differential and maximum allowable pressure. Then match the materials and process connection to the medium, and assess the electrical connection, ingress-protection class and any required explosion-protected version or approval.

Key attributes are setting range, switching pressure, switching differential, maximum pressure, medium compatibility, process connection, electrical connection, ingress-protection class and available explosion-protected or approved version.

FAQ

A mechanical pressure switch operates an electrical contact by converting the pressure mechanically and does not need its own power supply. An electronic pressure switch uses a pressure sensor and power supply, provides a switching contact and may display the current pressure.

Switching differential, also called dead band or switching hysteresis, is the pressure difference between switching on and off. A fixed differential prevents the contact from switching back too quickly. Pressure control may use a switch with a limited adjustable differential.

Define the required switching pressure first. The switching point should preferably be between 20% and 80% of the setting range and is specified at rising pressure. Also verify that the maximum allowable pressure exceeds the highest process pressure.

Select a vacuum switch when the switching point lies in a vacuum range. Use a differential-pressure switch when the difference between two pressures determines the switching action. For either type, match the range, differential, maximum pressure and process connection to the system.