SCH - Mechanical Pressure Switches

Mode of Operation

The pressure applied in the sensor housing (1) acts on the measuring bellows (2).

Pressure changes lead to movements of the measuring bellows (2) which are transferred through a pressure pin (4) to the switching rocker (5). The switching rocker is supported on hardened pivot points (6).

As the pressure increases the switching rocker (5) moves upwards and operates the micro-switch (7). The spring (8), the initial stress of which can be changed by the setting screw (9) (switching point setting), acts as opposing force. The travelling nut (10) is moved by turning the setpoint spindle, and the initial stress of the spring (8) is changed. The screw (11) serves for the internal adjustment of the micro switch. The counterpressure spring (12) ensures stable switching behaviour, even for low setting values.

• 1 = pressure connection
• 2 = measuring bellows
• 3 = sensor housing
• 4 = pressure pin
• 5 = switching rocker
• 6 = pivot points
• 7 = microswitch or other switching elements
• 8 = setpoint spring
• 9 = setting spindle (switching point setting)
• 10 = travelling nut (switching point indicator)
• 11 = adjusting screw for microswitch
• 12 = counterpressure spring

Pressure Sensors

With few exceptions in the low pressure range, all pressure sensors are equipped with measuring bellows, partly made of a copper alloy but mostly in high stainless steel quality (1.4571). In comparison with the permissible values, the measuring bellows are subject to low loads and move only slightly. This results in long service life with low switching point drift and high overpressure safety. The movement of the measuring bellows is also restricted by an international stop so that the forces resulting from the overpressure cannot be transmitted to the switching mechanism.

The parts of the sensor in contact with the medium are welded together without additional materials and the sensors contain no seals. Cu bellows which are used for low pressure ranges are soldered to the sensor housing. The sensor housing and all parts in the unit in contact with the medium can also be manufactured completely in stainless steel 1.4571 (series DNS). The individual data sheets contain exact data on materials.

Pressure Connection

The pressure connection is designed in accordance with DIN 16288 for all pressure switches (pressure gauge connection G ½ A). They can also be connected optionally to the interna thread G ¼ in accordance with ISO 228 Part 1. Max. screwdown depth on the internal thread G ¼ = 9 mm. Differential pressure switches have two pressure connections (max. and min.) and must be connected to one internal thread G ¼ each.