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measureing temperature of power resistors using current.

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Tonkabot:
I have a TO220 power resistor used to heat a gas manifold.    The resistor is 50 ohms, we have a fixed 24v supply.
I can turn on and off the power to the resistor, and I can measure the current through the resistor.   I can also calculate the number of Ohms the resistor currently has.

I want to use this current feedback to get an idea of how hot my gas manifold is, because of course we know the resistor value changes with temperature.

How accurate temperature measuring can expect to get out of this system?   16 bit ADC on the current.

Thanks!

Benta:

--- Quote from: Tonkabot on May 16, 2022, 07:42:21 pm ---because of course we know the resistor value changes with temperature.

--- End quote ---

How do you know this? Normally, power resistors are optimized to keep a constant resistance over temperature. Is this a special type?

Tonkabot:
Well, I don't know it.   I assumed it...
But looking at the power resistors specs, your right, they design for a low temperature coefficient.

I would need resistors that are not optimized for a low Tc.   Or better yet,  something like a TO220 PTC or NTC  power thermistor.

TimFox:
It would be far easier to use a calibrated thermistor probe, or a thermocouple or RTD sensor, or a semiconductor device (for lower temperatures).
See  https://www.omega.com/en-us/resources/integrated-circuit-sensors  for a range of solutions.

Benta:
I agree with TimFox. Keeping heating and sensing separate is a much better and safer solution.
BTW, which kind of "gas manifold"? That could mean anything.

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