In the field of industrial automation control, capacitive pressure transmitters are key equipment for measuring pressure parameters. They can convert the sensed pressure signal into a standard electrical signal output for subsequent monitoring, control, and analysis. So, what are the components of a capacitive pressure transmitter?

　　1. Sensitive components - capacitor film box

The capacitive membrane box is the core sensitive component of a capacitive pressure transmitter, consisting of two movable electrodes and one fixed electrode, with an insulating medium filled in between. When the measured pressure is applied to the membrane box, the membrane box will undergo elastic deformation, causing a change in the distance between the two movable electrodes and the fixed electrode. According to the calculation formula of capacitance C=ε S/d (where C is the capacitance, ε is the dielectric constant, S is the electrode area, and d is the electrode spacing), changing the electrode spacing will cause a change in the capacitance value. There is a certain functional relationship between the capacitance change and the measured pressure, thus achieving the conversion of pressure signal to capacitance signal.

　　2. Measure the circuit

The main function of the measurement circuit is to convert the small capacitance changes generated by the capacitive film box into electrical signals that are easy to measure and transmit. It usually includes parts such as oscillation circuit, demodulation circuit, and amplification circuit. The oscillation circuit generates a high-frequency alternating signal, which is applied to the capacitor film box, making the capacitor film box a variable capacitor and participating in the oscillation circuit. When the capacitance value changes, the frequency or amplitude of the oscillating circuit will also change accordingly. The demodulation circuit is responsible for extracting information related to capacitance changes from the oscillating signal and converting it into a DC signal or a low-frequency AC signal. The amplification circuit amplifies the demodulated signal to improve its strength and stability for subsequent output and processing.

　　3. Conversion circuit and output circuit

The conversion circuit further converts the signal output by the measurement circuit into a standard electrical signal, such as a 4-20mA DC current signal or a 1-5V DC voltage signal. These standard signals have good linearity and anti-interference ability, making them easy to connect and communicate with various display instruments, recorders, controllers, and other devices. The output circuit is responsible for outputting the converted standard signal to external devices, and can also provide some protection functions, such as overvoltage protection, overcurrent protection, etc., to ensure the safety and reliability of signal transmission.

The capacitive pressure transmitter consists of a capacitive diaphragm box, a measurement circuit, a conversion circuit, and an output circuit. The various parts cooperate with each other to achieve accurate measurement and conversion of pressure signals, providing important technical support for industrial automation control.