Characteristics and Temperature Error of Semiconductor Strain Gauge

Semiconductor strain gauge is a sensitive element made of the piezoresistive effect of semiconductor single crystal silicon, also known as semiconductor strain gauge. The piezoresistive effect is a phenomenon in which the resistivity of a semiconductor crystal material changes when it is deformed by a force in a certain direction. The semiconductor strain gauge needs to be pasted on the test piece to measure the strain of the test piece or pasted on the elastic sensitive element to indirectly feel the measured external force. Mechanical quantities such as stress, strain, pressure, torque, acceleration, etc. of various objects can be measured by using elastic sensing elements of different configurations. Compared with resistance strain gauges, semiconductor strain gauges have the advantages of high sensitivity coefficient (about 50 to 100 times higher), small mechanical hysteresis, small size, and low power consumption.

1. Characteristics of semiconductor strain gauges

When the semiconductor material is subjected to stress, the resistance value will change, and the resistance value change is mainly caused by the dimensional change and the resistivity change. The relative change is primarily determined by the relative change in resistivity. The sensitivity of the semiconductor strain gauge is very high, but its resistance temperature coefficient is large, and the sensitivity also changes with the temperature change, which is prone to thermal zero drift and thermal sensitivity drift.

2. Reasons for temperature errors of semiconductor strain gauges

Under the condition that the strain gauge is not stressed, when the working environment temperature changes, the relative change of resistance will also be caused. The measurement circuit (usually using a Wheatstone bridge) has an output, which produces a temperature error, and the semiconductor strain gauge produces a temperature error. The main reasons are as follows:

(1) The influence of the temperature coefficient of resistance.

(2) The influence of different linear expansion coefficients of specimen material and strained material. When the strain gauge is used, it should be pasted on the specimen. If the linear expansion coefficient of the specimen material and the strain gauge material are different, the strain gauge will produce additional deformation and additional resistance when the ambient temperature changes. When measuring the strain with a semiconductor strain gauge, a bridge circuit is generally used. Initially, the bridge is in a balanced state (ie zero point). When the temperature changes, due to the existence of the temperature coefficient of resistance of the strain gauge and the linear expansion coefficient of the strain gauge and the specimen Different, the resistance of the strain gauge changes, the bridge deviates from the equilibrium state, and there is an output without feeling the strain, which is called thermal zero drift. When the temperature changes, the false strain caused by the temperature change should be compensated.

(3) The effect of temperature on the sensitivity of semiconductor strain gauges.