Film strain gauges, varistors and ceramic measuring cells Measuring principle

There are three methods of pressure measurement: film strain gauges, varistor and ceramic measuring cells.

Film strain gauge

As a resistive sensing element, the film Wheatstone bridge is directly connected to the stainless steel diaphragm. The action of the external pressure bends the diaphragm, which changes the resistance of the Wheatstone bridge. The change in resistance is in turn converted to a signal proportional to the pressure.
This method allows for the accurate measurement of high burst pressures and even for shock or vibration environments.

Varistor sensor

The varistor sensor is protected by hydraulic oil and the stainless steel diaphragm isolates the sensor from the media. The action of the external pressure causes the diaphragm to bend, resulting in a change in the pressure of the hydraulic oil. At this point, the sensor emits a signal proportional to the pressure, which in turn is converted to an output signal of 4-20 mA.
This sensor is suitable for low pressure measurements.

Ceramic measuring battery

Unlike film strain gauges, the Wheatstone bridge is directly connected to the ceramic diaphragm. The external pressure causes the diaphragm to bend, thereby changing the resistance of the Wheatstone bridge, which in turn translates into a signal proportional to the pressure.

Ceramics have a high chemical resistance and are suitable for corrosive media. The measurement range is higher than that of the film strain gauge, but the precision is not as good as the film strain gauge.