Capacitive pressure sensor is a kind of pressure sensor that uses capacitance as a sensitive element to convert the measured pressure into a capacitance value change. This kind of pressure sensor generally uses a round metal film or gold-plated film as an electrode of the capacitor, when the film feels the pressure and deforms, the capacitance formed between the film and the fixed electrode changes, and the electrical signal can be output with a certain relationship between the voltage through the measurement circuit.
Capacitive pressure sensor belongs to the polar distance variation capacitive sensor, which can be divided into single capacitive pressure sensor and differential capacitive pressure sensor.
The single-capacitive pressure sensor is composed of a circular film and a fixed electrode. The film deshapes under the action of pressure, thereby changing the capacity of the capacitor, and its sensitivity is roughly proportional to the area and pressure of the film and inversely proportional to the tension of the film and the distance from the film to the fixed electrode. The other type of fixed electrode is concave spherical shape, and the diaphragm is a tensioning plane fixed around the periphery. The diaphragm can be made by the method of plastic gold plating. This type is suitable for measuring low pressure and has high overload capacity. A single capacitive pressure sensor can also be made of a diaphragm with a piston moving pole to measure high pressure. This type reduces the direct compression area of the diaphragm so that a thinner diaphragm can be used to improve sensitivity. It is also integrated with various compensation and protection sections and amplification circuits to improve anti-interference capability. This sensor is suitable for dynamic high pressure measurement and telemetry of aircraft. Single-capacitive pressure sensors are also available in microphone type (i.e. microphone type) and stethoscope type.
The pressure diaphragm electrode of the differential capacitive pressure sensor is located between two fixed electrodes to form two capacitors. Under the action of pressure, the capacity of one capacitor increases and the other decreases accordingly, and the measurement result is output by a differential circuit. Its fixed electrode is made of a gold-plated layer on a concave curved glass surface. The diaphragm is protected from rupture by the concave surface during overload. Differential capacitive pressure sensors have higher sensitivity and better linearity than single-capacitive pressure sensors, but they are more difficult to process (especially to ensure symmetry), and they cannot achieve isolation of the gas or liquid to be measured, so they are not suitable for working in fluids with corrosive or impurities.
Post time: Jun-19-2023