The induction coil outside diameter usually defined by markings on the induction cooktop generates a toroidal field from outside edge to inside edge that is intended to be "pulled into" the inductive material on the bottom of the pan. The inductive material has some resistance, so current induced by thealternating field flowing through the pan bottom causes pan heating. How well the field is contained by the pan depends on its material and by its size relative to the hob diameter.

In the linked YouTube video, the cast iron pan is undersized relative to the hob, so some field lines may not be completely contained in the pan base. It is even possible that the induced field is saturated in the base thereby forcing some lines to remain outside of the base. It is possible that the reaction field is partly emitted from the pan base upper surface. Various steels used in induction cookware may be better at dealing with the field density than cast iron.

There is a steel compound called mu-metal that is exceptionally good at trapping field lines, but it wouldn't be functional at high temperatures of cooking. Anyway, my last course on this subject was taken in 1964, so a more theoretical explanation would likely miss important points.

Thus, given a field not fully trapped in the base, part of the field is free to interfere with electronics that aren't well enough shielded. Trying to use the thermometer next to an AM radio transmitting tower might yield similar results, although the frequencies differ by a factor of more than 10.

For the described experiment, does your pan overlap the hob diameter? What is the brand of the pan? Does this happen with other (possibly noname) thermometer probes? I'll have to test this myself next time a suitable cooing condition occurs. I wonder whether a thermocouple probe would be affected (electronics display is a few feet away from the probe end).

I'm more interested in the pastrami. The number of local "delis" that cure their own pastrami has rapidly dwindled. Most are buying from meat purveyors such as Boars Head or other companies like them. Kudos to you for keeping the pastrami story alive.

I used a Cuisinart Stainless Steel pan that is approved for induction, on a Wolf (newer model) induction cooktop. The pan diameter is about 1 inch less than the hob diameter. I only have a Thermopop, so i don't know what would happen with other thermometers.

What surprised me was that the Thermopop was so far above the bottom of the pan (at least 4 inches).

Here's the statement from Thermoworks on this problem:

We’ve discovered that some models of induction cooktops can create temporary interference with digital electronic thermometers when they are placed near the range while the cooktop is powered on. The good news is that the interference shouldn’t cause any permanent damage to your ThermoPop or your cooktop.

If you experience interference, here are some things you can try to get a reading:

1. Try to insulate the pot clip and probe to reduce any interference.
2. Or, briefly turn off the induction cooktop during the reading.
3. Or, remove the food from the cooktop to take a quick reading away from the magnetic field.

The amount of interference you experience and the solution that works best will depend on the model of induction cooktop you use.

What do you think of this? I really appreciate your taking the time to educate me.

I've never thought of making my own pastrami, but now I want to. As it happens, I have a Coleman stove-top smoker that I haven't used in years -- I recently looked at it and thought "hmmm....maybe it's time to get rid of it". But now I have a new reason to keep it. I'm going to make pastrami! (I already have the rye bread recipe down, and have been making that all Covid-time.)

repac wrote, in part: "What do you think of this? I really appreciate your taking the time to educate me."

You are welcome, but I don't have much more I can say about it until I try a few experiments. Due to other ongoing projects, results may be obtained sometime between 'in a while' and 'in the fullness of time.' Also, my results will be limited to any interaction that exists between my Frigidaire (Electrolux) cooktop, my various pans, and my various thermometers.

Do you get the same effect over an undersized hob?

Did you come across any similar complaints about other brands of digital thermometers?

Kaseki,

A quick look online reveals numerous complaints about erratic behavior ("berserk") with electronic thermometers used over induction cooktops. Most complaints were for Thermoworks thermometers, but also saw that Taylor and Polder gave similar results.

Here's what one responder stated: "The nature of thermocouples used in those digitals makes them perfect antennae to pick up your induction hob."

I will check tomorrow whether a pan on an undersized hob gives the same result. Though I'm anxious to try the experiment, sleep is winning me over right now.

Toronto Veterinarian,

Let us know how the pastrami turns out! Enjoy.

I'm not sure that these minimal thermometers are thermocouples. I would expect thermistor based designs, but have no actual information on this point at the present.

Experiment 1: Taylor 9845 vs. Frigidaire 36-inch Gallery cooktop. Pan is on the small hob, undersized by about 1/2 inch radius. Pan is by Revere Ware, drawn stainless steel, works on induction, may not fully entrap field lines due to metal thinness. (This pan's manufacture precedes residential induction by decades.) Pan is heating water for boiling eggs; hob is operating at boost setting. No effect on the thermometer was observed with the tip in the water or over the uncovered coil edge or the thermometer electronics just outside the pan in various orientations near the hob edge.

Kaseki,

Here are my evaluations of the effect of hob size/pan and Thermopop placement on Thermopop function. BTW, the Cuisinart pot is heavy and thick.

1. Filled a 10" pot with >4" water, brought to a boil on an 8" hob on HI. Thermopop could not measure water temp in the pot accurately when hob was on, and it usually turned itself off then on during or after temp assessment. Taylor digital thermometer (9847N) measured water temperature accurately with hob on or off.

The pot isn't flat across all 10" (probably close to 9" flat surface), so the overlap on my smallest hob (8") isn't large. To compensate, I put only half of the pan on the hob, the rest was on the vacant cooktop space next to the hob. This left about half of the hob uncovered. With this setup, the following tests were carried out.

2. Turned the hob on to HI or 3 increments and tested the water temp near the edge of the pan farthest from the working hob. Thermopop failed to measure temp accurately while hob was on. Once the hob was turned off, temp measurement was accurate.

3. Turned the hob on to HI or 3 increments, placed a plastic cup with an ice/cold water mix over the uncovered portion of the working hob, and measured the temp in the cup. Thermopop failed to measure the temp in the cup accurately.

4. Turned the hob on to HI or 3 increments, then tested the airspace over the uncovered part of the hob. At first the temp assessment was within expectation, but continued testing in this way produced several inaccurate results and caused the Thermopop to turn off then on. While the number of tests on the uncovered hob was not large (fewer than 10), it appeared that the Thermopop failed more frequently when it was measuring water temp instead of air temp. FYI, prior evaluations of the Thermopop measuring air temp showed it to be reasonably accurate.

I performed intermittent testing of the Taylor digital thermometer in tests 2 - 4, and it was reasonably accurate each time.

Thoughts?

Thought (only have one tonight): The Thermopop is poorly designed for operation in whatever field exists over your induction cooktop, whereas the Taylor, either accidentally or deliberately, is relatively immune. My impression is that the cooktop may be emitting EMI sufficient to disturb the Thermopop even if a pan over a hob fully traps the field lines from the coil.

This may have been part of your testing, but in case it wasn't, try this: Heat water in a pan on a hob that the pan overlaps. Put warm water in another pan and set it on a different hob that is off. Try to measure the temperature of the warm water. If that fails with the Thermopop, see how far from the cooktop (operating) you have to move the thermometer to get it to remain functional.

Continued...

Experiment 2: Taylor 9845 vs. Frigidaire 36-inch Gallery cooktop. RevereWare Pan is on the small hob, undersized by about 1/2 inch radius etc as in Experiment 1. Pan is heating water for boiling eggs; hob is operating at boost setting. An Emeril fry pan is on the middle larger hob. This fry pan bottom is 1.5 inches smaller in radius than the hob boundary lines. Again, no interference apparent on the Taylor 9845 around either pan, including bringing the Taylor under the fry pan lip so it is immediately within the field at the cooktop surface.

Yet to be done: Interference experiment with ThermoWorks ThermaQ digital thermocouple device with exposed and shielded probes.