The differential pressure transmitter is a remote pressure measuring instrument that converts the pressure difference into a DC standard signal, widely used in industrial production and scientific research, and is a hardware for obtaining, processing, and transmitting various kinds of information. With the continuous improvement of the level of enterprise automation, its application is more and more extensive, and more and more problems are encountered in production. According to the author's many years of practical experience, in order to properly install, use, and maintain the differential pressure sensor, it is necessary to understand its working principle, and determine how it performs data collection and common troubleshooting methods. 1. Working principle and monitoring system 1.1 Working principle The differential pressure from the double-sided pressure pipe acts directly on the diaphragms of the transmitter's sensors. It is conducted to the measuring element through the sealing fluid in the diaphragm. The measuring element converts the measured differential pressure signal to correspond to it. The electrical signal is passed to the converter and processed through amplification into a standard electrical signal output. Several differential pressure transmitter application measurement methods: (1) combined with the throttling element, use the differential pressure value generated before and after the throttling element to measure the liquid flow; (2) use the pressure difference of the liquid's own gravity to measure the liquid The height; (3) direct measurement of the pressure difference between the different pipes and tanks. 1.2 Monitoring System Through the pressure device, the pressure signal is introduced into the differential pressure transmitter, and the differential pressure transmitter converts the signal into an electrical signal output of 0-5V or 4mA-20mA, and is converted into a digital signal output by the A/D conversion module. The A/D conversion module adopts Beijing Dingsheng Lichuang R8017. The digital signal output by R8017 is converted into a computer-recognizable signal by the data communication module R8520 and input into the computer. The specific hardware structure is shown in Figure 1. The R8017 is an 8-channel analog acquisition module. The input is a 0-5V DC voltage or a 4mA-20mA DC current signal. The R8520 module uses 9-pin data cable and serial port communication for RS232/RS485 conversion module and computer connection. Set the address of each module, read the data for each channel of each module, and processed by computer software to obtain monitoring data. 2, troubleshooting Differential pressure transmitters often have some faults in the measurement process. The timely determination, analysis and processing of faults are crucial to the equipment being used. To a certain extent, it affects the normal production and even jeopardizes production safety. According to the author's years of practical experience, summed up some common fault determination analysis and solution. 2.1 Line failure When the value displayed on the computer is abnormal, first open the differential pressure transmitter's junction box and check whether the line is virtual, short or disconnected. You can determine the fault by measuring the power supply, measuring resistance, and shaking insulation. deal with. 2.2 Acquisition Module or Differential Pressure Sensor Failure When troubleshooting the line, it depends on whether the acquisition module or differential pressure sensor is faulty. Use a multimeter to check whether the differential pressure transmitter working power is normal, and at the same time, measure whether the output voltage of the differential pressure transmitter is within 4mA to 20mA (if the output voltage value is, whether the measurement is in the range of 0-5V), and confirm whether the output value is normal. If there is no output value, the differential pressure transmitter is damaged and the differential pressure transmitter needs to be replaced. If the on-site measured value conversion matches the actual experience value, there will be no problem with the field instrument and the measuring point, the module is damaged, and the module needs to be replaced. When the on-site measured value conversion is the same as the computer display value, there is a problem with the pressure tube or differential pressure transmitter. 2.3 Pressure tube failure (1) Pressure tube clogging In the actual production and use and maintenance, due to the timeliness of the discharge, or the medium is dirty, sticky, or with particles, powders, etc., it takes a long time, and some will solidify, causing the pressure tube to be clogged and the measurement cannot be performed normally. Therefore, in order to ensure the normal operation of the transmitter, it is necessary to periodically try to clear the pressure tube. (2) Leakage of the pressure pipe Due to the relatively large number of accessories such as differential pressure transmitter contacts and globe valves, leakage points increase and maintenance workload increases. Therefore, it is necessary to reasonably do a good job of anti-corrosion of the pressure pipe and reduce the appearance of trachoma in the pressure pipe. The joints of the pressure pipe should be tightened to prevent loosening. (3) Pressure effusion Because the pressure of the gas flow is not taken or the installation of the pressure tube is not in compliance with the requirements, the phenomenon of liquid accumulation inside the pressure tube is often caused. The appearance of this phenomenon will often result in inaccurate measurements. If the transmitter has a small range, it may even cause some fluctuation in the output of the transmitter. Some literatures have pointed out that the correct installation of the pressure tube should be continuous with the gradient with the level not less than 1:12, there is a height difference between the measurement point and the installation point, and the pressure taking point should be perpendicular to the wall of the device under test. In order to make the measurement more accurate, a number of pressure measuring heads can be set. All the pressure measuring heads are connected together to form a pressure equalizing pipe, which is then led out through the pressure guiding pipe. A discharge valve is arranged at the lowest point of the pressure equalizing pipe. In addition, during the actual production and use of the site, there will also be problems such as the heat-supply of the pressure pipe and the reverse of the pressure pipe. 2.4 frequency conversion interference In the process of field installation and wiring, signals bundled together or walk the same multi-core cable, the signal will be disturbed, especially the signal line and the power line with a long pipeline in the interference. In this case, the differential pressure transmitter will appear on the scene without communication, or even misinformation. Therefore, during the installation process, similar misoperations should be avoided, and the distance between the instrument cable and the power cable tray should be increased. 2.5 Electrical Signal Transmission Failure Because there are certain differences in the level of installation, use, and maintenance personnel, in order to save manpower, material resources, financial resources or consider other factors, the differential pressure transmitter is often placed in the vicinity of the device under test, causing the transmission distance of the electrical signal is too far, making There are interference and attenuation phenomena in the electrical signals. Therefore, it is necessary to appropriately increase the cross-sectional area of ​​the cable to solve this problem. 3ã€Conclusion The working principle and parameter monitoring system of the differential pressure transmitter were discussed above, and the common faults in the production process were analyzed. The on-site installation, maintenance, and use of personnel can only eliminate the occurrence of faults and improve the quality of maintenance from the roots if they have mastered the above knowledge. Pulley Conveyor Pulley,Belt Pulley,Conveyor Belt Pulley,Drive Belt Idler Pulley SHIJIAZHUANG VITURE IMPORT AND EXPORT TRADING CO.,LTD ,