The working principle of the strain gauge in a vacuum pressure switch

Vacuum pressure switches usually do not rely on strain gauges to achieve pressure detection. Their core principle is to trigger the microswitch through mechanical deformation elements such as diaphragms and bellows, rather than the resistance change of the strain gauge. However, some specially designed vacuum pressure sensors may integrate strain gauge technology, and their working principle is as follows:

A strain gauge is a sensitive component whose resistance changes with mechanical deformation. Its working principle is based on the piezoresistive effect of metals or semiconductors. When the strain gauge is subjected to pressure, its geometric dimensions (length, cross-sectional area) and resistivity change, resulting in a alteration of the resistance value. In vacuum pressure detection, strain gauges may be adhered to elastic diaphragms or beam structures. When the vacuum pressure changes and causes the diaphragm to deform, the strain gauge deforms accordingly, and the resistance value changes accordingly. The resistance changes are converted into voltage or current signals for output through circuits such as Wheatstone Bridges, thereby achieving the measurement of vacuum pressure.

However, it should be noted that traditional vacuum pressure switches mainly operate by triggering microswitches through mechanical deformation. When the vacuum pressure within the system is higher or lower than the set pressure, the pressure sensor (such as diaphragm, bellows, etc.) deforms. Through mechanical structures (such as balustrade springs), the microswitch is activated, and an electrical signal is output to control the start and stop of the equipment. This mechanical structure features high reliability and fast response speed, and is suitable for working conditions such as frequent starts and stops.

Strain gauge technology is more widely applied in high-precision pressure sensors. These sensors precisely sense pressure by measuring the resistance changes of strain gauges, but they are costly and structurally complex, and are usually not the mainstream technology for vacuum pressure switches. Therefore, when discussing the working principle of vacuum pressure switches, the differences between them and traditional strain gauge pressure sensors should be distinguished.