The post explains a simple temperature to voltage converter circuit using IC LM317. The idea was requested by one of the dedicated members of this blog.

Technical Specifications


I have eurotherm TS200A temperature controller.this is thyrister based.

This required 0-5V control voltage. I want one temperature control circuit when temperature is 25deg C the voltage is 0V. Temperature reduces the control voltage increase from 0-5V.

Please provide the circuit diagram.

Thank you.

The Design


A simple layout for the proposed temperature to voltage converter circuit can be seen in the following diagram.



LM334 which is a precision temperature sensor chip is configured with another precision voltage regulator IC LM317 circuit forming an accurate, linear temperature to voltage converter circuit.

The gain pot and R2 may be tweaked and experimented for achieving the desired temperature to voltage ratio.

As per the request, the voltage needs to be 0 at 25 degree C, this may be done by creating an atmosphere at the specified temperature and then adjust the pot to get a 0V at the output.

The above adjustment would hopefully allow the output to produce 1V increment for every 4.16 degree decrease in the temperature around LM334, this may also need some tweaking.

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