Ntc thermistor manipulation

I have a junk dishwasher I want to experiment on outside. the documentation says the wash temp is 145°f. the sanitize temp is 155°f for 9 minutes.

Just for the heck of it I would like to trick the computer and make the ntc thermistor show 140°f instead of 160°f to make the dishwasher sanitize and wash temp a little higher.

How can I manipulate the ntc thermistor resistance to do this?

Could this be done with a resistor?

I guess a better question would be, How/can I calibrate the ntc thermistor reading without modifying software parameters? The thermistor reads about 20°f too high

NTC (negative temperature coefficient) means the resistance goes down as the temperature goes up.

Adding a series resistance will raise the total resistance making the temperature reading lower than it really is. But this will change all of the measurements in a non-linear way and it could foul-up other functions.

You can estimate the resistance you have to add to shift the temp 10°F.

Measure the thermistor at "room" temperature ~20 °C
There are a limited number of NTC's and you can usually identify the NTC by this resistance.

Most common is 10K at 20°C, others are 2K, 1K etc.

Look on line for a typical NTC with your 20°C value and see the difference in resistance between the two temps you are trying to shift. add the difference to your circuit in series with your NTC.

This is not perfect solution as there are some special NTC with different slopes but I think if you go with a typical you will be pretty close.

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