A differential pressure manometer detects the difference between two pressures. The measuring element, e.g. a Bourdon tube, is connected to two chambers, each of which contains one of the two media to be compared. If the pressures in both chambers are equal, the differential pressure manometer will show no signal. Only if the two pressures differ from each other will the measuring element move, and with it the pointer showing the absolute value of the pressure difference.
The differential pressure manometer can be equipped additionally with a switch function to trigger an action in high overload application for example. A differential pressure manometer with switch function or electrical contact device controls pre-selectable minimum and/or maximum pressure values and initiates an action once the value is reached. Usually differential pressure manometer for these kind of applications are in robust design to withstand use in tough environments (Dust, vibrations, high temperatures etc.) or as safety version per EN 837-1 S3.