There are many types of electrical interference in the industrial production process automation system. The industrial field instrument should be designed to consider the interference treatment of each electrical port. Here, the isolation sensor is recommended for the signal anti-interference treatment of the analog signal input and output port of the industrial instrument. The solution for bus interference transceivers is recommended for the anti-jamming processing of communication bus interfaces for industrial meters. A variety of automated instruments, computers and corresponding actuators are used for production process monitoring and control. The signals in the process have small signals ranging from weak to millivolts, large signals with tens of volts, and even signals up to several thousand volts and hundreds of amps. In terms of frequency, there are DC low frequency ranges and high frequency/pulse spikes. Mutual interference between equipment and instrumentation has become a problem that must be solved in system debugging. In addition to electromagnetic shielding, solving the "ground" of various equipment meters, that is, the potential difference of the signal reference point, will become an important issue. Because the signals of different devices and meters are to be transmitted and transmitted to each other, there is a problem of signal reference points. In other words, for the complete transmission of the signal, the ideal situation is that the signals of all equipment meters have a common reference point, that is, the potential difference between the reference points of all equipment instrument signals is "zero." However, in the actual environment, this is almost impossible. In addition to the voltage drop caused by the wiring resistance between the "ground" of each equipment meter, there are still various equipment instruments that are subject to different interferences in different environments. And the wire contacts are subjected to wind and rain, resulting in a drop in the quality of the joints, and so on, resulting in a difference between the "grounds". In the industrial production process control system, the industrial field instrument needs to monitor the electrical signal transmitted by the front-end sensor, and also needs to transmit the processed signal to the control center host. In order to ensure the reliability and stability of the signal transmission, it is necessary to consider the signal port. Isolation processing to eliminate the ground potential difference after the instrument is connected to the system. The industrial field instrument is used in the industrial production process control system, and its function is to sample the field sensor signal, calculate the sampled value according to the preset algorithm, obtain the value of the actual physical quantity monitored, and pass the actual physical state of the field through the communication bus or The 4~20mA current signal is output to the main control center. Its general system composition diagram is shown below. figure 1 As can be seen from the above figure, the sensor signal is input to the industrial instrument, firstly the EMC protection circuit. Due to the complicated electrical environment of the industrial site, there are strong electrical equipment (such as high-power motor) and high-frequency switching equipment (such as frequency converter). When the device starts and stops, it will generate large surges and spikes. This kind of interference contains relatively large energy. It absorbs such interference through EMC protection devices such as varistor and TVS tube to protect the latter stage. The circuit will not be damaged by such interference. The sensor signal is input into the isolation amplifier of the input terminal through the EMC protection circuit to isolate and condition the signal. The signal isolation can ensure that the internal circuit of the instrument and the external sensor form a ground line block, eliminating common mode interference, thereby eliminating the ground line caused by the ground potential difference. Circulation, on the one hand, ensures that the sampling accuracy of the sensor signal is not affected by interference. On the one hand, it can protect the internal MCU system from damage caused by large common-mode voltage; signal conditioning, signal type conversion and signal amplification The signal is linearly amplified to meet the signal type and range of the ADC sampling, ensuring that the conditioned signal range matches the ADC signal input range, thereby ensuring the ADC sampling accuracy. The MCU performs digital calculation on the sensor signal digitally quantized by the ADC, and obtains the actual condition of the physical quantity of the field after a series of operations such as digital filtering and linearization operation, and then outputs it to the display panel, and simultaneously obtains the physical quantity of the field according to the linear ratio. Output to the DAC circuit, the DAC circuit output voltage signal, in order to form a 4~20mA current signal, it is also necessary to isolate the voltage signal into a 4~20mA current signal output through an isolation amplifier at the output end. Of course, the signal output also needs to design EMC protection circuit. Industrial intelligent meters generally have communication interfaces. At present, there are common 485 communication interfaces, CAN communication interfaces, which can directly upload the physical quantity of the field through the communication bus, and can also complete the parameter setting and instrument operation through the bus interface. Status inquiry, self-calibration of the instrument, etc. 485 communication and CAN communication use differential signal communication, which has strong anti-interference ability, but the common interface input voltage range that communication interface IC can withstand is limited, especially 485 interface IC, generally at -7V~+ Between 12V, in long-distance communication, the common mode interference formed by the ground potential difference is likely to cause damage to the communication interface IC, so the communication interface must also be isolated to improve system reliability. 4G Module,4G Router Module,4G Wifi Module,4G Lte Wifi Module Shenzhen MovingComm Technology Co., Ltd. , https://www.movingcommiot.com