add comments

Lab_1/TwoSensorsAAR.ino

@@ -17,7 +17,7 @@
 float adc_to_voltage(int n_adc);
 float kelvin_to_c(float k);
 float resistance_to_temperature(float r);
-float voltage_to_resistance(float v);
+float voltage_to_thermistor_resistance(float v);
 float voltage_to_erc(float v);
 
 void setup() 
@@ -34,12 +34,12 @@ void loop()
 	thermistor_val = analogRead(ThermistorPin);
 	thermocouple_val = analogRead(TCpin)
 	// Calculate thermistor temperature in degrees C ( Part b, i,ii,iii & v)
-	thermistor_temp = kelvin_to_c(resistance_to_temperature(voltage_to_resistance(adc_to_voltage(thermistor_val))));
+	thermistor_temp = kelvin_to_c(resistance_to_temperature(voltage_to_thermistor_resistance(adc_to_voltage(thermistor_val))));
 
 	// Calculate thermocouple temperature in degrees C ( Part c, i - iv)
 	e_rc = 1000*voltage_to_erc(adc_to_voltage(thermocouple_val)); // convert to millivolts
-	e_comp = NISTdegCtoMilliVoltsKtype(thermistor_temp);
-	thermocouple_temp = NISTmilliVoltsToDegCKtype(e_rc + e_comp);
+	e_comp = NISTdegCtoMilliVoltsKtype(thermistor_temp); // eqn (6) lab prep sheet
+	thermocouple_temp = NISTmilliVoltsToDegCKtype(e_rc + e_comp); // eqn (7) lab prep sheet
 
 	/* Display results.  Don't use printf or formatting etc., they don't work on the Arduino. Just use 
 	   the serial print statements given here, inserting your own code as needed */
@@ -55,7 +55,7 @@ void loop()
 /* Write a function to convert ADC value to 
    voltage: put it here and use it in your code above*/
 float adc_to_voltage(int n_adc) {
-	return (float)n_adc*V_REF/1024.0;
+	return (float)n_adc*V_REF/1024.0; // eqn (1) lab prep sheet
 }
 
 
@@ -66,23 +66,29 @@ float kelvin_to_c(float k) {
 }
 
 
-float resistance_to_temperature(float r) {
+// Convert Resistance (Ohms) to Temperature (Kelvin) (for thermistor)
+float resistance_to_thermistor_temperature(float r) {
 	// Define Thermistor constants
-	float t_0 = 298.15;
-	float r_0 = 10000;
-	float b = 3975;
+	float t_0 = 298.15; // Kelvin
+	float r_0 = 10000; // Ohms
+	float b = 3975; // Kelvin
 
-	return 1.0 / ( (1.0/t_0) + (1.0/b)*log(r/r_0));
+	return 1.0 / ( (1.0/t_0) + (1.0/b)*log(r/r_0)); // eqn (3) lab prep sheet
 }
 
 
-float voltage_to_resistance(float v) {
-	return 1000*((10.0*3.3/v)-10.0);
+// Convert Voltage (Volts) to Resistance (Ohms)
+float voltage_to_thermistor_resistance(float v) {
+	float pull_down_resistance = 10; // kOhms
+	float v_hi = 3.3; // Volts
+
+	return 1000*((pull_down_resistance*v_hi/v)-10.0); // eqn (4) lab prep sheet
 }
 
 
+// Convert Voltage to E_RC
 float voltage_to_erc(float v) {
-	return (v-0.35)/54.4;
+	return (v-0.35)/54.4; // eqn (5) lab prep sheet
 }