① The sensitivity coefficient of piezoresistive sensors is 50-100 times greater than that of metal strain sensors. Sometimes the output of a piezoresistive sensor can be measured directly without an amplifier.
② Because it is processed by integrated circuit technology, the structure size is small and the weight is light.
③ High pressure resolution, it can detect small pressure as small as blood pressure.
④ Good frequency response, it can measure pulsating pressure of tens of kHz.
⑤ Since the force-sensitive element and detection element of the sensor are made on the same silicon chip, it works reliably, has high comprehensive accuracy, and has a long service life.
⑥ Because the semiconductor material is made of silicon, the sensor is more sensitive to temperature. If temperature compensation is not used, the temperature error is large.
There are two types of piezoresistive sensors: one is to use a bulk material of a semiconductor material to make a paste-type strain gauge to form a semiconductor strain sensor; the other is to use a semiconductor material to make a diffused resistor using an integrated circuit process , Forming a sensitive element, is called a diffused piezoresistive sensor.
The piezoresistive sensor is greatly affected by temperature, and it will produce zero drift and sensitivity drift, which will cause temperature error.
In the piezoresistive sensor, the temperature coefficient of the diffusion resistance is large, and the resistance value changes with temperature, which causes the zero drift of the sensor.
The temperature drift of the sensor sensitivity is caused by the piezoresistance coefficient changing with temperature. When the temperature rises, the piezoresistance coefficient becomes smaller, and the sensitivity of the sensor decreases, otherwise, the sensitivity increases.
Zero temperature drift can generally be compensated by series and parallel resistors.
Sensitivity temperature drift is compensated by connecting a diode in series with the power circuit of the bridge.
In addition, the piezoresistive sensor can also connect four diffusion resistors into a full bridge. In order to reduce the effect of temperature, a constant current source can be used to supply power.
It can be seen that the output of the bridge is directly proportional to the change in resistance, that is, proportional to the measurement, and also proportional to the power supply current. The output voltage is related to the size and accuracy of the constant current source current, but has nothing to do with temperature. Good temperature compensation.