Study On Dynamic Response Characteristics Test Method And System Of Micro Rapid Humidity Sensors

As the Intelligence develops,the fields,such as transportation,health care,building,environment,meteorology,industry and so on,require that the humidity measurement and control is more precise.As the key element,not only the static humidity characteristics of the sensor are good,but also the dynamic characteristic is fast.Recently,as the development of industrial production level and the deep study on the humidity sensor,the static characteristics of the humidity sensor have been improved greatly,but their dynamic characteristic can not meet the requirements of some fields,such as fuel vehicles,respiratory diseases care and so on,due to the slow improvement of the dynamic characteristic.There are many factors which influences the dynamic characteristic improvement of the humidity sensor,but one of key factors is the tested system.At present,the results show that some test systems for the dynamic characteristics are difficult to popularize due to their complex construction and cost,and others have some flaws,such as unstable humidity,long time to balance,slow conversion and single test process.According to the constant humidity principle at a temperature and pressure,humidity generation method based on the saturated salt solution has such good characteristics as stable humidity,low cost,simple system,easy balance and good repeatability,and the method is internationally accepted,but the air stratification in the space above salt solution is often observed.Based on the above analysis,this paper carried out the following research.Firstly,the saturated salt solution method is chose to design and build the system of humidity by comparative analysis of the humidity generation method and the characteristics of the system,and the moisture stratification is tested.Secondly,the mixing device is used because of the phenomenon of air moisture stratification in saturated salt solution humidity generator.At the same time,the mixing device can mix the saturated salt solution in order to improve the homogeneity of solubility of the saturated salt solution,and the moisture stratification of the saturated salt solution humidity generator is tested.Thirdly,the humidity switch control and measurement system of humidity sensor test chamber was designed,so that the humidity of humidity sensor test chamber can jump abruptly.Beside,the test of elevating humidity and removing humidity test are simple.Fourthly,two simple feasible precise inexpensive system scheme and test method of using pump and fan instead of "pump and mixed gas fan” to drive gas circulation are determined.According to the two plan of humidity sensor dynamic performance test system of humidity sensitive processing platform.Fifthly,the main performance of this system is studied by testing the humidity sensor.Through the research,the following conclusions are drawn:(1)When the aerofoil-shaped mixing fan mixes the air slowly,the stratification of saturation point of the system can be avoided,and the best position Hc = 6 cm of the air intake is in the upper space,which is deviated from the wall.(2)The batch mixing balance method can help the saturated salt establish stable humidity fixed point more quickly.(3)The design of humidity switching device can solve the dynamic test problem of slow switching speed,irreversible test and humidity sensor of the different response time.The response time of humidity sensor dynamic test system is less than 211.345 ms.The test repeatability is less than 7.3%.The test system uncertainty is less than 1.46%.The test system of using fan instead of air pump and mixed air fan is simpler and cheaper,but it needs be further perfected and improved in terms of accuracy and stability.