To bring the UV1 in a acceptable range for calibration you need to place a resistor and the cable length gives a very small resistance
which works out really well and this gave me a standardised measurement
You can use any temperature sensor all you need to do is locate like you have done the thermistor and carefully remove the thermistor and connect
a screen cable to this then follow the instructions about the UV conversion,
UVR128 is my second choice for the modification have not got round to it yet,
is any chance you could take some close-up pictures of the circuit board and circuitry
