Calibrating a thermistor at home with ds18b20 e.g.

[leenowell]

Hi All,

I am trying to create a food thermometer using thermistor based food probes I bought online similar to these (https://www.ebay.co.uk/itm/373143679317). The trouble is that I couldn't find any that come with any specs/ data sheets so having to deduce them myself. For this I need 3 good temperature/ resistance readings to calculate the steinhart coefficients.

I have tried using a known good thermometer which uses a similar probe, waiting for it and my ESP readings to stabilise and then using the temp on thermometer and the calculated resistance. I am not sure whether my probes are waterproof so rather than using the water based methods I used fridge, room temp and a number of temps up to 100C from a lidded saucepan. Trying to use a variety of these to calculate the coefficients and then using them to calculate others gives temperatures nowhere near the readings I got.

Thinking now maybe the thermometer isn't any good, I was thinking if a ds18b20 (or something similar) is already calibrated is it worth buying one of these and using that to determine the temperature and redo my process?

Anyone have any other ideas?

Many thanks in advance

Lee.