Piston-type differential pressure gauges are available with one or two hermetically sealed leaf switches. The switches are adjustable within a defined percentage of the full scale of the meter and are available in SPDT and SPST, normally open or normally closed configurations for various load / power classifications.

Operation principle:

The differential pressure p1 and p2 are given in the ports HP and LP and in the chambers of measurement media separated by magnetic piston under pressure resp. Magnetic piston and separation diaphragm.

The pressure difference causes an axial movement (measurement path) of the piston supported by a measuring range spring and indicates the respective DP value.

A magnetic ring mounted on the gauge of the instrument follows the movement of the magnets on the piston, so that each position of the piston fits a defined position of the gauge.

This design guarantees the complete mechanical separation of the measuring system and the box and eliminates external leaks.

The above figure also has an additional blade switch that is useful for taking a contact output for a required DP value.