| Real-time and effective detection of volatile organic compounds(VOC)in the air is of great significance to production and life.In the military field,detecting the fuel leakage of satellites and missiles;in the civilian field,real-time monitoring of the leakage of chemical raw materials and the excess of harmful substances in the air requires high-precision detectors for detection.Photo Ionization Detector(PID)has become the mainstream detector for convenient VOC gas detection in various fields based on its advantages such as wide measurement range,high measurement accuracy(ppb level)and convenience,and it has also become one of the current hot research topics.This paper starts with the development of PID at home and abroad,summarizes the gap between domestically produced PID and foreign countries,takes the photoionization theory as the starting point,and uses the working principle of PID as a means to deeply analyze the related materials,including electrode materials,circuit structure,etc.The influence of parameters on detector performance.Based on the above analysis,a miniaturized,convenient and long-term stable use solution is proposed.The details are as follows:(1)Aiming at the problem of PID life and long-term use instability,the paper first establishes a life prediction model to conduct corrosion experiments on four corrosion-resistant materials,and selects the most stable material as the electrode material of the PID,which can prolong the service life of the detector.(2)The circuit is modularized,and the UV lamp driving circuit module is designed to be packaged separately.Only the UV lamp transparent window is close to the ionization chamber to reduce the interference of the generated magnetic field on the weak current detection module;design the voltage demodulation circuit module And humidity detection module,the purpose is to accurately grasp the PID response to isobutylene and the impact of environmental factors on its performance when the detector is calibrated;the special shell structure is designed to keep more gases to be detected in the ionization chamber,and at the same time,It is easy to disassemble when cleaning the UV lamp.(3)Establish a special calibration system to eliminate the interference of temperature and humidity on PID calibration.Use the calibrated PID to test the acetone and calculate its response coefficient(RF),and verify the universality of PID by comparing the standard response coefficient.Through the detection of PID initial values in different temperature and humidity environments,the best use environment for the PID designed in this paper is determined.After the above efforts,the corrosion performance comparison of PID electrode material,circuit design and production,structural design and production,and sensor calibration test have finally been completed.The test results show that PID has good repeatability,hysteresis and long-term stability.The best use environment of PID.It provides a feasible scheme for the domestic batch production of PID. |
