I'm trying to find a part number for an NTC thermistor being used to monitor the temperature of a rechargeable battery. The thermistor I have has no color markings or numbers to indicate any information. I have measured the resistance at multiple temperatures, but I am worried my calculations are not very accurate, as I just used an ice cube and the hot surface of a food warmer. I need to ensure that the resistance - temperature curve matches the one of the thermistor I have, so that the battery charges when it should. Is there any sort of tool made to reliably produce different temperatures for measurement, or a better way I could go about this?
If you can wrap the thermistor in a waterproof heatproof enclosure (say, copper pipe soldered shut on one end) then an easy way to produce known temperatures is to use water's phase changes.
- Boiling water is at 100 °C (with correction for your local air pressure based on altitude).
- A mixture of water and ice (neither all melted nor all solid) is at 0 °C (after the water, if added separately, has cooled down; better but slower to let the ice melt to make the water).