Calibrating Temprature value.

Dear all.

I have attached ADC output w.r.t to temperature reading. I am looking for equation which gives me accurate value for input & output

For Positive value i get proper & accurate reading but for negetive reading i am getting offset

i am giving input from calibrator & output reading on 4 segment Display

kindly share some equation for same

unsigned int ProDegrs=0;

void Degree_cov()
{
   if( ADCdisplay>=8000 && ADCdisplay<=9989)
            {
             ProDegrs=0.0323*ADCdisplay-258.32; Minus=0;
            }
        else
            if(ADCdisplay>=18654)
            {
                   ProDegrs= 0.0361*ADCdisplay- 313.51; Minus=0;
            }
            else if(ADCdisplay>9989 &&ADCdisplay<11080) 
            {
                    ProDegrs= 0.0329*ADCdisplay- 264.42; Minus=0;
            } else if(ADCdisplay>4664 &&ADCdisplay<7999)
                  {
                      // LEDBuffer[3] = DISPTABLE[14];
                      Minus=1;
                      ProDegrs=0.0313*ADCdisplay-251.09;
                     
                  }
                  else 
                  {
                    ProDegrs=0.0344*ADCdisplay-282.66;Minus=0; 
                  }


}

For Negative value are mentionrd in excel sheet

if(ADCdisplay>4664 &&ADCdisplay<7999)
                  {
                      // LEDBuffer[3] = DISPTABLE[14];
                      Minus=1; 
                      ProDegrs=(0.0313*ADCdisplay-251.09)+202;
                     
                  }

Input Output on isplay
-100 -100
-90 -112
-80 -122
-70 -132
-60 -142
-50 -152
-40 -162
-30 -172
-20 -182
-10 -192

Degree_1.pdf (55.2 KB)

Neg_reading.pdf (112 KB)

Few Queries:

1. Are you using Arduino UNO?
2. What is the resolution in bit of your ADC?
3. Is the ADC unipolr or bipolr?
4. What is the FS of your ADC?
5. What is the VREF voltage of your ADC?
6. What is the ADC value for temperature T10C (say, 250C)?
7. What the ADC value for temperature T20C (say, 400C)?
8. What is the ADC value for temperature T30 (say, -100C)?
9. What is the type no. of your temperature sensor? Do you have any idea about its response curve?