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how to connect thermocouple  with a micro controller

alexvarghese

for measuring temperature from 0 to 150 degree . i am using attiny85 controller . what kind of driver should i use . what kind of thermocouple should i use ...

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    Hi Alex,

    Thermocouples produce pretty low voltages - for example a K type might generate just over 6 millivolts at 150 degrees C. This means you need an amplifier with a gain of about 700 to get good resolution from your A/D converter. They only generate a signal that is proportional to the difference in temperature between the 2 ends of the wire, so you need to know the temperature at the amplifier end in order to calculate the temperature at the sensor end.

    Another issue is they are not quite linear, so if you need the best precision you need to correct for the non-linearity. As other have mentioned thermistors might be a bit easier to use. Another alternative is a semiconductor temperature sensor like an LM35. They can measure up to 150 degrees C and have a high level output that does not need amplification. They typically output 10 millivolts per degree so 150 degrees would cause the output to be 1.5 volts. They are pretty simple to hook up - 3 wires - ground, 5 volt power and the signal wire goes to an A/D pin.

    Doug

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    Hi Alex,

    Thermocouples produce pretty low voltages - for example a K type might generate just over 6 millivolts at 150 degrees C. This means you need an amplifier with a gain of about 700 to get good resolution from your A/D converter. They only generate a signal that is proportional to the difference in temperature between the 2 ends of the wire, so you need to know the temperature at the amplifier end in order to calculate the temperature at the sensor end.

    Another issue is they are not quite linear, so if you need the best precision you need to correct for the non-linearity. As other have mentioned thermistors might be a bit easier to use. Another alternative is a semiconductor temperature sensor like an LM35. They can measure up to 150 degrees C and have a high level output that does not need amplification. They typically output 10 millivolts per degree so 150 degrees would cause the output to be 1.5 volts. They are pretty simple to hook up - 3 wires - ground, 5 volt power and the signal wire goes to an A/D pin.

    Doug

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