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.
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.