These devices are suitable for use cases involving shocks at the installation location, in contaminated media, and for mobile operation in any location. The use of a pitot tube enables even lower flows to be monitored. The flexible bellows seal prevents the function from being affected by metal chips, which are to be anticipated during lubricating oil checks on gear units.
In the chamber upstream of the tube, the medium, which enters in the arrow direction, generates a stagnation pressure that moves the diaphragm system in the direction of flow. This movement actuates the switch contact by means of a bellows-sealed lever; the switch point for type 776 is fixed, and that for type 778 is fixed or adjustable.