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Connection method of displacement sensor and PLC control system
The linear displacement sensor based on potentiometer principle is a linear displacement sensor with sliding rheostat structure. The sensor can supply 5V or 10V power, output 0-5V, 0-10V voltage signal, or 12-24V power supply. It is equipped with transmission module to output 0-5V, 0-10V, 4-20mA analog signal, which is convenient to connect with PLC control system for processing and calculation.
The common wiring methods of displacement sensor are: two wire system, three wire system and four wire system. The displacement sensor with 4-20mA current signal can adopt two-wire wiring method. The power supply, sensor and analog input module are connected in series. Only two wires are needed for power supply and signal connection between the sensor and PLC, which are both power lines and signal lines. Because the starting current of the two-wire signal displacement sensor is 4mA, it provides the static working current for the sensor. At the same time, the electrical zero point of the acquisition system is 4mA, which does not coincide with the mechanical zero point, which is conducive to identify circuit faults such as power failure and short circuit. The two-wire system is also convenient for the use of safety barriers, which is conducive to safety and explosion-proof.
The three wire connection method can be used for the displacement sensor with voltage signal and 4-20mA current signal. The positive end of the power supply uses a wire, the positive end of the signal output uses a wire, and the negative end of the power supply and the negative end of the signal share a wire.
The four wire connection method can also be used for the displacement sensor with voltage signal and 4-20mA current signal. Due to the popularity and application of 4-20mA DC (1-5V DC) signal system, in order to facilitate the connection in the control system application, it is required that the signal should be unified. Therefore, some measurement and control instruments should adopt the output of 4-20mA However, due to the complex conversion circuit and high power consumption, it is difficult to fully meet the design requirements of two-wire transmitter, so the four wire connection method with external power supply can only be used. Two wires of four wire displacement sensor are responsible for power supply, and the other two wires are responsible for signal transmission.
For users, the sensor selection should be based on the PLC
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