The performance difference between diffusion and pump suction gas detectors
The detection principle of the diffusion type and the pump suction gas detector is basically the same. The sample gas is detected by the sensor of the instrument, and then the corresponding value is displayed on the screen after being amplified and sorted by the circuit. Catalytic combustion sensors are commonly used for flammable gases, and electrochemical sensors are commonly used for toxic gases. The difference between the diffusion type and the pump suction type is the sampling method.
Diffusion gas detector is to detect the gas in the area to be detected and slowly flow the sample gas into the instrument with the free flow of air, and it needs to be placed on site. This method is affected by the detection environment, such as ambient temperature, wind speed, etc., and is not suitable for air sources with low pressure. The advantage of the diffusion gas detector is that the cost is lower than that of the pump suction type.
The pump-suction gas detector is equipped with a gas sampling pump. The working method is that the power supply drives the gas sampling pump to extract and sample the gas in the area to be measured, and then send the sample gas into the instrument for detection. The pump-suction gas detector is characterized by fast detection speed, long-distance measurement of dangerous areas, and maintenance of personnel safety. It is suitable for occasions where the gas detector cannot be placed on site, and where there are special requirements for response speed and pressure difference.
The gas sampling pump is an important running part of the pump-suction gas detector, which is directly related to the life and reliability of the instrument. Gas detectors generally use small and micro volumetric gas pumps. During the design, the micro air pump is selected according to the requirements of flow rate, pressure, power, isolation from the sample, no leakage, light weight, low noise, electromagnetic compatibility, and service life. At present, there are many low-end gas sampling pump manufacturers in China, and the low-end market is almost occupied by domestic products. The high-end gas sampling pumps are dominated by imported KNF, Thamos and domestic "Qihai" brands.
From a technical and economic point of view, it is best to match the life of each part of the detector. Generally, in portable instruments, the lifespan of LEL sensors is longer, generally about three years; the lifespan of photoionization detectors is four years or longer; the lifespan of electrochemical specific gas sensors is relatively short, generally between one year and Two years; the life span of the oxygen sensor is the shortest, about one year. The life of the electrochemical sensor depends on the dryness of the electrolyte, so if it is not used for a long time, sealing it in a lower temperature environment can prolong its service life. The fixed instrument is relatively larger in size, and the life of the sensor is longer. There are many models of gas sampling pumps, and the service life of products from different manufacturers is also quite different. Some domestic manufacturers lack technical input, and the design and material selection of the micro pumps they manufacture are poor, with short service life and many failures. Even if the requirements such as flow pressure and other requirements are temporarily met, reliability cannot be guaranteed, and some even simply imitate foreign pumps in appearance. The domestic Qihai brand miniature gas sampling pump is of good quality. Life and reliability are at the leading level in China. The service life and reliability of its adjustable-speed pumps equipped with brushless motors can compete with well-known international brands.
