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This is not exactly about electrical circuitry, but I hope it's close enough not to get me kicked out. Please redirect me if necessary.

Almost all induction tops advertise possibility to "keep temperature", usually in 10°C steps, so I guess that is the precision they can measure temperature with.

I would like to understand HOW temperature is measured and what are actual limits of technology, including precision.

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    \$\begingroup\$ Have you read: en.wikipedia.org/wiki/List_of_temperature_sensors ? The thermistor and thermocouple might be the most likely candidates for use in an induction cooker. There is no "everyone uses..." as it depends on the design. Accuracy depends on technology but also calibration, many sensors can accurately sense a 1 degree temperature change but not be able to tell you exactly the value of the temperature without proper calibration. \$\endgroup\$
    – Bimpelrekkie
    Commented Feb 11, 2019 at 12:11
  • \$\begingroup\$ Thanks @Bimpelrekkie, I am well aware of "classical" temperature measurement components; I seemed to understand, however, that in this case temperature was indirectly measured from the induction coils themselves. If this is not the case then question is moth. \$\endgroup\$
    – ZioByte
    Commented Feb 11, 2019 at 12:18
  • \$\begingroup\$ Do they actually measure the temperature, or just hold the power output steady enough that the temperature stays steady? If you can regulate the power output and keep it from wandering, then the user can set it to what ever power level is needed to cook at the desired temperature. Gas stove tops work that way - no temperature measurement, but a continuously adjustable flame lets you easily adjust for a particular dish. \$\endgroup\$
    – JRE
    Commented Feb 11, 2019 at 13:01
  • \$\begingroup\$ The control is not great. I put a cast iron pan on a 1kW hob and set the temperature to 120C. I measured the temperature with an IR thermometer pointed at the middle of the pan and the power with an energy meter in the AC line. The pan went straight up to 170C, the power cut off, the pan fell to 110C very slowly, power on, shot up to 170C, and continued like that. Plus the outside of the hob was 30C cooler than the centre. \$\endgroup\$
    – emrys57
    Commented Jul 4, 2020 at 10:11

2 Answers 2

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I think the best way to measure temperature on induction cookers is to use IR diodes. Using classical NTC (or PTC) is very tricky due to the ceramic glass.

These diodes are relatively cheap, and the circuitry is basic (some Op Amp for the amplification of the diode signal)

A publication can be found on the subject here

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At least some of them appear to have a silicon thermistor set in the center of the induction coil and (probably mostly radiatively **no, see below) thermally coupled to the pot.

Here is a photo of a replacement Chinese-made one from this site:

enter image description here

**Edit: The sensor is slathered with heatsink compound and in thermal contact with the bottom of the glass. Screen capture from this video.

enter image description here

From another video, a different (IKEA 2kW) cook top:

enter image description here

Whilst an IR sensor might be better under controlled conditions (though that's dubious in general given the very low emissivity of many pot bottoms) it's probably too expensive to use on typical induction cook tops.

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