A strain gage is a sensitive device that converts the strain change on the device under test into an electrical signal. It is one of the main components of a piezoresistive strain sensor. The most widely used resistance strain gauges are metal resistance strain gauges and semiconductor strain gauges. The metal resistance strain gauge has two kinds of filament strain gauges and metal foil strain gauges. Usually, the strain gauge is tightly bonded to the mechanical strain matrix by a special adhesive. When the stress changes due to the force of the substrate, the strain gauges are also deformed together, so that the resistance of the strain gauge is changed, thereby The voltage applied to the resistor changes. The strain gauges typically have a small change in resistance when stressed. Typically, such strain gauges form a strain bridge and are amplified by a subsequent instrumentation amplifier and transmitted to the processing circuit (usually A/D conversion). And CPU) display or actuator.

It consists of a base material, a metal strained wire or a strained foil, an insulating protective sheet, and a lead wire. Depending on the application, the resistance of the strain gauge can be designed by the designer, but the range of resistance should be noted: the resistance is too small, the required drive current is too large, and the heat of the strain gauge causes the temperature to be too high. Used in different environments, the resistance value of the strain gauge is changed too much, the output zero drift is obvious, and the zero adjustment circuit is too complicated. The resistance is too large, the impedance is too high, and the ability to resist external electromagnetic interference is poor. Generally, it is about tens of euros to several tens of kiloohms.

Resistance strain gauge sensors have two applications:

It is used as a sensitive component for direct measurement of the strain of the test piece; the other is used as a conversion component, and the sensor is constructed by an elastic component for indirect measurement of any other physical quantity that can be converted into strain of the elastic component. The strain gauge used as the sensor should have higher requirements, especially the nonlinear error is less <0.05%~0.1%F.S.

Resistance strain gauge sensors have the following application features:

(1) Wide application and measurement range. Various strain sensors can be made with strain gauges. For example, the load cell can measure 10-1~107N, the pressure sensor can measure 103~10Pa, and the acceleration sensor can measure 103m/s2.

(2) Resolution (1με) and high sensitivity, especially with semiconductor strain gauges, sensitivity up to tens of mV/V; high precision (generally up to 1% to 3% FS, high precision up to 0.1% to 0.01% FS ).

(3) The structure is light and small, and has little influence on the test piece; it has strong adaptability to complex environments, and it is easy to implement isolation or compensation for environmental interference, so that it can be in special environments such as high and low temperature, high pressure, high speed, strong magnetic field and nuclear radiation. Use; good frequency response.

(4) Commercialization, convenient selection and use, and easy to achieve long-distance, automated measurement.

Therefore, although there are many types of sensors at present, high-precision sensors are still most commonly used in strain gauge applications. It is widely used in automatic measurement and control or scientific experiments in the departments of machinery, metallurgy, petroleum, construction, transportation, water conservancy and aerospace. In recent years, it has also been developed and applied in the fields of biology, medicine, sports and commerce.