This is a small breakout board to measure the temperature from a thermocouple. Photo’s and sample code below.
Some background on Thermocouples
Thermocouples generate a tiny voltage that is non-linearly proportional to the temperature difference between the tip and the rest of the thermocouple. There are different types of thermocouple, but J and K types are the most common. On Ebay the K types are available and cheap, so this board works with K type thermocouples. The voltage is tiny so needs amplification. It’s non-linear so needs to be processed. It’s also generating a voltage difference across the length of the thermocouple, so this board to also measure the temperature at the base (cold junction) and compare it against the tip voltage.
The AD 8495 amplifies K types, cold junction offsets and has a simple linear output. The voltage out is simply 5mV / degree Celsius. So 20 degrees is 100mV and 100 degrees is 500mV. Nice and simple. This also reduces the number of connections from a microchip or development board as we only need ground, input voltage (3v to 18v) and the output reading. At the other end of the board we insert the thermocouple (ensuring it’s the right way around)
In summary:
- Simple output 5mV / degree Celsius, no need for libraries
- 3v to 18v input
- GND input
- Thermocouple +/- input
- Tiny current draw of 0.18mA (you can power it from a microchip pin)
- 19mm x 27mm
- Accurate to +/- 2 Celsius
- Ambient (the board) temperature 0-50 degrees Celsius
- K Type Thermocouple 0 to 400 degrees Celsius
// Arduino Leonardo example code
int analogPin = 0;
int val = 0; // variable to store the value read
float temperature; // Allow to play with the values
void setup()
{
Serial.begin(9600); // setup serial
}
void loop()
{
val = analogRead(analogPin); // read the input pin
temperature = float(val);
temperature = temperature * 1024 / 1000; // convert the 1024 bit ADC
Serial.println(val); // debug value
delay(500); // slow it down a bit
}
'Picaxe example code for thermocouple breakout 'Running from 5V supply 'Each increment = 5 / 1024 = 0.00488v main: readadc10 c.2, w1 'Read the current ADC into w1 w2 = w1 * 488 / 500 'Convert w2 to temperature debug 'View the value on the debug screen pause 200 goto main