NTC Thermistor Testing Method for Automobile Air Conditioning

NTC thermistor is a resistor that decreases with increasing temperature. Due to its high sensitivity, high accuracy, and high reliability, thermistors are widely used in various temperature measurement, temperature control, and temperature compensation. The most important thing for NTC thermistors is that they can maintain stable long-term operation under ultra-high temperature and high pressure conditions. Thermistor according to the different temperature resistance and heat resistance and differ somewhat. NTC thermistor is widely used in automobile electronic controller, especially the car air conditioning, lithium battery management system (BMS) and auto power controller and so on need to apply to the thermistor module.

However, the resistance value of NTC thermistor is nonlinear with temperature, so it is difficult to test in practical application.

Nowadays, there is a new invention aims to provide a NTC thermistor test method used for automotive air conditioning. It can according to the actual situation of automobile air conditioning thermistor temperature, through the RT table data validity evaluation of thermistor polynomial fitting analysis, and gives a set of suitable for RT table data applications.

The invention adopts a technical solution of an automotive air conditioner test method for an NTC thermistor. According to the selected Steinhart - Hart, the equation of third order polynomial fitting formula and NTC thermistor manufacturers RT table data values for fitting analysis.

When the residual difference between the fitting data and the original data exceeds the preset threshold value, the NTC thermistor should be reviewed. In addition, NTC thermistors with less data in RT table are used to modify the RT table data by using the method of piecewise interpolation of characteristic curves.

Finally, after software filtering, a new set of RT table data is presented, which can provide reference for the selection of NTC thermistor.