Working principle of capacitive pressure transmitter

Introduction to capacitive pressure sensors: The continuous development of science and technology has greatly enriched the types of pressure measurement products. Now, the sensitive principles of pressure sensors include not only capacitive, piezoresistive, metal strain, Hall, vibrating cylinder, etc. However, capacitive, piezoresistive and metal strain sensors are still the most common. Metal strain gauge pressure sensor is a kind of piezocapacitance pressure sensor with a long history. Introduction: The continuous development of science and technology has greatly enriched the types of pressure measurement products. Now, the sensitive principles of pressure sensors include not only capacitive, piezoresistive, Metal strain type, Hall type, vibrating cylinder type, etc., but still capacitive, piezoresistive and metal strain type sensors are the most common. Metal strain gauge pressure sensor is a kind of pressure sensor with a long history, but due to its shortcomings such as hysteresis, creep and poor temperature performance, its application is greatly restricted. Piezoresistive sensor is a new type of sensor manufactured by using semiconductor piezoresistive effect. It has the characteristics of convenient manufacturing and low cost. However, because the semiconductor material is extremely sensitive to temperature, its performance is greatly affected by temperature, and the consistency of the product Poor. The capacitive sensor is the most widely used pressure sensor, and its principle is very simple. The capacitance value of an infinite parallel plate capacitor can be expressed as: Cu003d ε s/d (ε is the dielectric constant of the medium between the parallel plates, d is the distance between the plates, and s is the coverage area of u200bu200bthe plates) change one of them Parameter, you can change the capacitance. Due to the simple structure, almost all capacitive pressure sensors adopt the method of changing the gap to obtain variable capacitance. The initial capacitance value of a capacitive sensor is small, generally tens of picofarads. It is extremely susceptible to the influence of wire capacitance and the distributed capacitance of the circuit, so advanced electronic circuits must be used to detect small changes in capacitance. It can be said that a good capacitive sensor should be a perfect combination of variable capacitance design and signal processing circuit.