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Modify resistance of RTD sensor to PT100

Question asked by pcbsmoke on Feb 15, 2016
Latest reply on Apr 14, 2016 by pcbsmoke

I want to couple a Hakko 907 soldering iron with PTC thermistor sensor to a generic PID temperature controller. The soldering iron sensor range is approx from 45.9 ohms at zero degrees C to 145.8 ohms at 600 degrees C. The generic PID controller does not support this input but does support PT100. The corresponding range of a PT100 RTD is from 100 ohms at zero degrees C to 313.6 ohms at 600 degrees C. Is it possible to make a circuit which takes the input resistance from the soldering iron sensor and generates the correct output resistance for the PT100? The circuit would have to calculate the output resistance from known variables: input slope, output slope, input resistance at zero degrees C and output resistance at zero degrees C. I've worked out a formula, but I don't know how to go about it.


Any help would be appreciated. I was thinking the circuit may involve a digipot but I don't know the general direction to look or whether it is even possible or feasible.


Thanks in advance.