Automobile water temperature sensor uses NTC thermistor to measure the water temperature, which uses the characteristic that the resistance value of thermistor decreases as the temperature rises. Automobile NTC thermistor produced by EXSENSE Electronics Technology Co., Ltd. has the characteristics of high precision, high stability, fast reaction, etc. It plays the role of temperature monitoring and temperature controlling in automobile water temperature sensor.

Conventional automotive water temperature sensor on the market has a wide range of resistance value, which cannot ensure that a certain resistance value can be accurately identified within the full temperature range. They can only discard the less commonly used range, which leads to inaccurate data collection. In order to solve the above problems, EXSENSE Electronics introduces a temperature detection circuit using automotive NTC thermistor, which can effectively improve the existing automotive water temperature sensor due to the wide variation range of its resistance value, there is a technical problem of the blind area of inaccurate temperature collection. This temperature detection circuit includes NTC thermistor, two-circuit voltage acquisition circuit, volt current condenser (VCC ) and motor control unit (MCU).

Among them, the two-circuit voltage acquisition circuit include a series switching device and a pull-up resistor. Two-circuit voltage acquisition circuit is connected to one end of VCC and NTC thermistor in parallel; The other end of the NTC thermistor is grounded; The conduction control terminal of the switching device of the two-circuit voltage acquisition circuit is respectively connected to two EN pins (Enable Pin) of the MCU. The two EN pins of the MCU are at different high or low levels during normal operation and at the same high level after hibernation. The pull-up resistor of the two-circuit voltage acquisition circuit is between the upper and lower limits of the working resistance of NTC thermistor. The upper and lower limits of the resistance values of the NTC thermistor in the precise concern zone and the inaccurate concern zone of the NTC thermistor are obtained by the R-T table of the NTC thermistor at the set temperature. The resistance values of the pull-up resistor of the two-circuit voltage acquisition circuit are the intermediate values of the upper and lower limits of the resistance values of the two concern zones obtained respectively. A filtering circuit is formed between the NTC thermistor and the A/D end of the MCU. The filtering circuit is RC filter circuit.

This temperature detection circuit, two-circuit voltage acquisition circuit is set on the NTC thermistor to detect the partial voltage of NTC thermistor. MCU is used to control the closed and open circuit of the two-circuit voltage acquisition circuit. Due to the resistance range of NTC thermistor in the full temperature range is large, pull-up resistor in voltage acquisition circuit uses different resistance values to realize the full temperature range composed of the precise concern zone and the inexact concern zone to realize the precise voltage division, the EN end of the MCU realizes the on-off control of the two-circuit voltage acquisition circuit, and the voltage on the NTC thermistor can be detected by collecting the voltage value accurately divided from the pull-up resistor. Then, the temperature value of NTC thermistor can be calculated by R-T table, so as to avoid the technical problem that the temperature collection of NTC thermistor is inaccurate.