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I have a 6VDC power source that is exciting an NTC Thermistor R1 (resistance of the thermistor decreases as the temperature increases, but the relationship is not linear). There is a precision resistor R2 between the positive side of the power source and the thermistor. These two resistors together result in a voltage divider circuit where the voltage drop across the thermistor changes linearly with temperature: Thermistor Volt Drop = (R1 / R1+R2)*Vin

This works fine, but the issue is that the particular thermistor that I'm using shouldn't have a voltage drop across it exceeding 3.2VDC or it risks self-heating (which would bias the temperature reading high). Replacing the current precision resistor with a higher resistance one would allow me to bring the thermistor's max realistic voltage drop below the 3.2VDC limit, but this is not an option - the precision resistor was specifically chosen because its resistance approximates the middle of the thermistor's temperature/resistance chart.

Is there anything that I can do to drop the voltage supply of the power source while maintaining the linear relationship between thermistor voltage drop and temperature? I have a few spare resistors laying around. Buying a 3VDC power supply is of course the easiest solution, but I work for local government and funds are not available for a while so I wanted to see if I could make do with what I have laying around.

Thank you.

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Is there anything that I can do to drop the voltage supply of the power source while maintaining the linear relationship between thermistor voltage drop and temperature?

Use a low drop-out linear voltage regulator to reduce the voltage and keep it more constant. A 3.3 volt linear LDO regulator should cost just a few pennies.

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