Research And Design Of NOx Sensor Performance Detection System

In view of the lack of effective performance testing instruments for domestic second-generation chip Nitrogen Oxide(NOx)sensors and the problems of single measurement type and limited accuracy in testing methods,the corresponding research has been carried out in this paper.Based on the theoretical research,a NOx sensor performance testing instrument has been designed,and a set of NOx sensor performance testing software based on LabVIEW has been developed.The NOx sensor performance testing instrument is composed of signal acquisition and control circuit,data acquisition card NI USB-6003 and milliampere digital ammeter.It realizes the testing of various indicators of NOx sensor.NOx sensor performance testing software based on LabVIEW realizes data analysis,storage,waveform display and control functions reflecting sensor performance.The research of control function includes the following two aspects:(1)Research on temperature control inside sensor.Firstly,on the basis of three-wire heating circuit,a comprehensive filtering method is studied to eliminate the interference of noise to the voltage signal.The accurate temperature signal can be obtained by temperature drift compensation and non-linear correction of resistance-temperature characteristic of filtered voltage signal.Then,the temperature inside the sensor is accurately controlled by means of the variable universe fuzzy adaptive PID control program.(2)Research on accurate detection of sensor performance.On the premise of keeping the temperature inside the sensor at 750 ± 2 ?,the sensor is placed in the corresponding gas atmosphere of a certain concentration.Stepping voltage is applied at both ends of the sensor signal resistance to measure the current value flowing through the signal resistance.Several groups of voltage and current values are collected and analyzed to obtain the parameters of linearity,sensitivity and limit current value of the sensor.The testing system completed in this paper provides a new type of testing instrument for domestic NOx sensors.It can accurately and rapidly detect whether many performance indicators of domestic second generation chip NOx sensors are qualified or not.Its function has been verified in the industrial field.It shows that the system hasmany advantages such as accurate testing,high intelligence,wide adaptability,stable performance and so on.