I have a 2k ohm sensor that fits properly but I can not find a proper 10k that fits a M14 hole for the water temperature on my car.
The gauge I am using only reads the NTC 10k thermistor so I was wondering if it was possible to convert the resistance. Bit new to the thermistor world.
Best Answer
Assuming the resistance-vs-temperature curves are proportional between the two thermistors, it is possible to make a ground-referenced 2k sensor behave like a ground-referenced 10k sensor. It just requires a bit of trickery with current mirrors.
simulate this circuit – Schematic created using CircuitLab
OA1 keeps the voltage across the 2k thermistor (R3) the same as the terminal voltage of the sensing circuit represented by V1. This causes a certain amount of current to flow through R2 and R3.
OA2 keeps the voltages across R1 and R2 the same. Since R1 is 5× the value of R2, this means that only 1/5 the current is required through R1, controlled by Q3.
Q4 mirrors the current through Q3 (these need to be matched transistors, kept at the same temperature, etc.). So, whatever voltage the sensing circuit applies to Q4, it behaves like R3, except with 5× the resistance.