An additional membrane which follows the movement of the pressure pin and has no function in normal operation is installed between the sensor and the switching mechanism.
Pressure is applied to the pressure bellows from the outside.
The effective area of the membrane is significantly larger than the area of the pressure bellows. Even with low pressure beneath the membrane caused by a leakage, a sufficiently large force is generated to actuate the microswitch. The sensor switches off to the safe side. In limiter functions it is frequently necessary to retain and lock the shutdown status and to release the lock and switch on the system again only after the causes that led to the safety shutdown have been eliminated. When the value set on the scale is reached, the microswitch switches over and remains in this position.