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AD8495 Thermocouple Amp - Reading Very Wrong Values
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AD8495 Thermocouple Amp - Reading Very Wrong Values

by Shyysiryxius on Sun Aug 11, 2019 3:58 am

Hi all,

After some stuffing about I finally got this thing working. Well sort off. It prints the temp to the serial display but the temperature it is reading in my room is -70 Deg C. Which is impossible. If I stick the probe in my mouth I can move it to maybe -60 Deg C but sill not even close to the real value. I can then add an offset to the code - I added 83 to the calculation and this gets me to the right value but it doesn't scale properly. The room temp as measured against a digital thermometer will be accurate but my mouth temp reading is maybe 6 Degress too low and when I measure 93 Deg C water it reads 63ish degrees

I have it setup to use 3.3V and basically followed the guide here:

https://learn.adafruit.com/ad8495-therm ... er/arduino

mirroring exactly what they had setup.

Thoughts?

Code: Select all | TOGGLE FULL SIZE
#define TC_PIN A0          // set to ADC pin used
#define AREF 3.3           // set to AREF, typically board voltage like 3.3 or 5.0
#define ADC_RESOLUTION 10  // set to ADC bit resolution, 10 is default
 
float reading, voltage, temperature;
 
float get_voltage(int raw_adc) {
  return raw_adc * (AREF / (pow(2, ADC_RESOLUTION)-1)); 
}
 
float get_temperature(float voltage) {
  return (voltage - 1.25) / 0.005;
}
 
void setup() {
  Serial.begin(9600);
}
 
void loop() {
  reading = analogRead(TC_PIN);
  voltage = get_voltage(reading);
  temperature = get_temperature(voltage);
  Serial.print("Temperature = ");
  Serial.print(temperature);
  Serial.println(" C");
  delay(500);
}

Shyysiryxius
 
Posts: 1
Joined: Sun Aug 11, 2019 3:52 am

Re: AD8495 Thermocouple Amp - Reading Very Wrong Values

by adafruit_support_mike on Sun Aug 11, 2019 2:03 pm

It sounds like you have the wrong kind of thermocouple. Are you positive it’s a type K?

adafruit_support_mike
 
Posts: 59172
Joined: Thu Feb 11, 2010 2:51 pm

Please be positive and constructive with your questions and comments.