Pressure switches with bourdon tubes are pieces of equipment with safety functions as set down in the Pressure Equipment Directive (PED). They are suitable for protecting the pressure device should the pressure rise above, or drop below, the approved boundary limits. They come under the remit of PED 1G Category IV and have been subjected to an EC type-examination. The requirements of Approval Certificate Pressure 100 from the German Technical Inspection Authority (VdTÜV) are met. These pressure measuring de- vices may only be operated with the electrical evaluation units set out below, and within the area of application of this certificate and the VdTÜV component identification number. The pressure switch is composed of the pressure measuring device and electrical evaluation unit. Because of its robust design, it is suitable for use in tough environments