NTC3950-10K temperature sensor

1. Calculation formula

Supplement:

B=3950

R=10K

T2=25 degrees

Check the RT table, 25 degrees corresponds to 10K

Circuit:

The thermistor and the pull-up resistor R813 divide the voltage to obtain the relationship between temperature and Vo voltage, and then convert the value to the MCU ADC based on Vo.

 Then substitute ADC for Rt to get the relationship formula between ADC and T.

 2. C implementation

NTC thermistor temperature calculation formula: Rt = R EXP(B(1/T1-1/T2))

Among them, T1 and T2 refer to K degrees, which is the Kelvin temperature.

Rt is the resistance of the thermistor at T1 temperature.

R is the nominal resistance of the thermistor at T2 normal temperature. The value of a 100K thermistor at 25°C is 10K (i.e. R=10K). T2=(273.15+25)

EXP is e raised to the nth power

B value is an important parameter of the thermistor

Through conversion, the relationship between temperature T1 and resistance Rt can be obtained, T1=1/(ln(Rt/R)/B+1/T2). Here, ln can be converted into log, that is, T1=1/(log(Rt/R)/B+1/T2).

The corresponding temperature in degrees Celsius is t=T1-273.15, with an error correction of +0.5.
First, we only need to know the resistance of the thermistor at the current temperature to calculate the temperature.
The hardware circuit is a simple series voltage divider circuit, so the resistance of the thermistor at the current temperature can be easily obtained through Ohm's law.
Below is the code implemented in C.

#include //Voltage converted to temperature void temp_data(void) { float Rt=0; //Rp pull-up resistor value float Rp=10000; //T2 is 25 degrees Celsius, converted to Kelvin temperature float T2=273.15+25; float Bx=3950; float Ka=273.15; float vol=0; vol=(float)(Get_Adc_Average(ADC_Channel_5,10)*3.3/4096); Rt=(3.3-vol)*10000/vol; temp=1/(1/T2+log(Rt/Rp)/Bx)-Ka+0.5; }

 PT100

Calibration:

Find the resistance values corresponding to PT100 at 0 degrees and 92 degrees as the calibration resistance values.

The temperature read by the software should be 0 degrees & 92 degrees. If there is a deviation in the value read, T0 & T92 will be used as the OFFSET value for software calibration.