ARDUINO SHIELD FOR TWO THERMOCOUPLES

 A0         0,1' connector     
 A1         0,1' connector     
 A2         0,1' connector      
 ARD_5V1    0,1' connector      
 ARD_GND1   0,1' connector              
 D2         0,1' connector      
 D3         0,1' connector      
 D4         0,1' connector      
 D5         0,1' connector      
 P1         4 mm female plug      
 P2         4 mm female plug      
 P3         Two port bord connector      
 P7         4 mm female plug      
 P8         4 mm female plug      

 IC1        LT1006       
 IC2        LT1006
 D1         LED      
 R1         10 k        
 R2         (see GAIN chapter)       
 R3         (see GAIN chapter)         
 R4         (see GAIN chapter)       
 R5         (see GAIN chapter)          
 R6         220         
 SW1        Push button     
 TH1        10 K TNC resistor     
 X1         BUZZER      

#define TEMP 1
#define CAN 0
#define N_CTN 4 // number of points in TNC calibration table 
#define N_TC 12  // number of points in thermocouple calibration table 
// Table calibration for THERMISTOR
float calib_CTN [N_CTN][2] = {
{340,15},
{395,19},
{405,20},
{470,30} // put here calibration points : first the value read on arduino ADC, second the value read on your reference thermoemter.
};
// Table calibration for THERMO COUPLE
float calib_TC  [N_TC][2] = {
{0,0}, // first point : at 0°C the TC give no voltage
{25,10},
{135,40},
{305,86},
{444, 125},
{580,160},
{616,170},
{655,180},
{709,195},
{734,201},
{841,231},
{888,261}
};

void setup() {
  // initialize serial communication at 9600 bits per second:

  Serial.begin(9600);
  pinMode(2,OUTPUT);
  pinMode(4,OUTPUT) ;
  pinMode(3,INPUT) ; digitalWrite(3, HIGH) ;
}

// the loop routine runs over and over again forever:
void loop() {
  // read the input on analog pin 0:
  int Can_comp = analogRead(A0);
  int Can_TC = analogRead(A1);
  float T_ctn = converti(Can_comp , calib_CTN, N_CTN);
  float T_Thcp = converti(Can_TC, calib_TC, N_TC) ;

    

  // print out the value you read:
  
  Serial.print("CTN ADC out ="); Serial.print(Can_comp);
  Serial.print("\tT ref ="); Serial.print(T_ctn);
  Serial.print("\tTcoup ADC out ="); Serial.print(Can_TC);
  Serial.print("\tTemp TC ="); Serial.print(T_Thcp);
  Serial.print("\t"); Serial.println(T_Thcp + T_ctn,2); // Temperature from Thermo couple is 
                                                            // added to cold junction temperature for compensation

  delay(100);        // delay for stability 
}

float Int_lin(float x,             // input : abcisse where the fonction is to be interpolated
              float X1, float Y1 , // Coordinates of lower interpolation point
              float X2, float Y2   // Coordinates of upper interpolation point
			  ){
  // linear interpolation : x beetween X1 and X2  
  // return interpolated value of y = f(x)
  float a , b ;  
  a = (Y1 - Y2) / (X1 - X2) ;
  b = Y1 - a*X1 ;
  return a*x + b ;
}

float converti(float X ,          // value read on ADC to convert in °C
               float calib[][2],  // Calibration table to use --> not the same for TCN en thermo couple
               int N
			   ){
	int i ;
	if (X < calib [0][CAN]){ // Entry outside calibration table (lower) --> extrapolation
	                         // with the two first points of table
		return Int_lin(X, 	
				calib [0][CAN], calib [0][TEMP] , 
				calib [1][CAN], calib [1][TEMP]) ;
	}
	if (X > calib [N-1][CAN]){ // Entry outside calibration table (higher) --> extrapolation
	                             // with the two last points of table

		return Int_lin(X, 	
				calib [N-1][CAN], calib [N-1][TEMP] , 
				calib [N][CAN], calib [N][TEMP]) ;
	}
	for (i=0 ; i < N ; i++){
		if (X < calib [i][CAN]){
			return Int_lin(X, 	
					calib [i-1][CAN], calib [i-1][TEMP] , 
					calib [i][CAN], calib [i][TEMP]) ;
		}
	}
}