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Induction Infarction

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During a holiday weekend cookout, I was involved in an accidental science experiment. I was attempting to fry homemade French Fries to go along with the BBQ ribs we were having for dinner. To minimize the odors and mess, I intended to fry the potatoes outside. I borrowed a portable induction cooktop from the kitchen shop where I worked and set it up on the porch.

I don’t own a traditional candy or deep-fry thermometer, so I use a remote temperature probe to check and maintain the oil temperature. The remote probe I own is a battery operated, combination digital timer and thermometer.

Setting up to begin cooking, I put the metal clamp on the side of the pan, set the temperature ranges and timer on the thermometer, ran the probe into the oil and turned on the induction cooktop.

Induction Cooktop Setup

My set up looked like this….

induction cooker probe set up

When the induction cooktop started, the probe went haywire. There were beeping sounds, screen changes, timers running, temperature range changes, it seemed the little probe was having a stroke.

Not being very smart, it took me a minute to assume the probe was too close to the cooktop and that the magnetic field might be interfering with the circuitry. So, I moved the probe farther away and it stopped freaking-out. Then, almost immediately, it began acting strangely again. Apparently, my fingers touching the probe cord was enough to interrupt the magnetic flow. I deduced that the magnetic field that was generating the heat with the pan was flowing into the metal clip, metal probe and cord interfering with the circuitry of the main thermometer unit.

I had no intention of sitting there holding the cord while trying to fry potatoes, so I moved the operation inside over the gas burners.

In addition to cooking meat, I use the remote thermometer probe to cook custard for ice cream, yogurt and oil frying. The latter three activities require clamping the probe to the side of the pan. Given that the magnetic field flows up that cord to the probe, you should not use these probes in this manner if using an induction cooktop.

If I hadn’t used my hands to interrupt the flow, I assume the digital circuits would have been totally fried at some point. I will also assume that any digital thermometer with a metal clamp would suffer the same fate.

Not being a scientist, I am not sure if the problem could be resolved by coating the clamp contact area with heat tempered silicone.

Regardless of the eventual solution, if you own a portable or fixed location induction cooktop, do not use digital temperature probes clamped to the side of your cookware.

You can use the probes in the oven or grill inserted into foods, as is most often done.

I have a call into a manufacturer regarding this issue and will report any findings in a future post.

***UPDATE: Shortly after I posted this information, I received a call back from a manufacturer of digital probes. They are aware that this problem exists and are changing their packaging to explain that the situation I describe above MAY happen. And this person, the president of the company interestingly, said that they are not sure if it happens because of the magnetic field strength or as a result of the direct transference of the energy to the probe. Nor are they certain if some induction cooktops may cause the problem more than others. The reason for the lack of specifics is that the manufacturers of induction cooktops are not interested in joint testing to determine how and why this happens with digital probes.

I was able to get the probe to work while holding the probe tip in the oil, with an oven mitt covered hand. So at least in my case, the general magnetic field wasn’t the cause. And, this person supported my assertion that all digital thermometers would suffer the same. It is the nature of the circuitry involved not a flaw in any one company’s product.

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4 Responses to “Induction Infarction”

  1. Gus

    Been wondering about this problem a lot – I don’t want fry to fry my beloved temperature probe. I’m glad to see my assumptions were correct. Being an electrical engineer, I can give you a few hints of what is likely happening: the induction field is causing current to flow in the body of the probe (just like it does in the body of the cookware to heat it). The current is not dangerous by itself (you won’t have a shock), but the high amps can fry any circuitry attached to it (the digital reader). To complicate things, the probe body is attached to an electrical wire (conductor) going to the reader, which is also subject to the same induction phenomena. The difference being that this one is highly conductive, so current flows higher (short-circuit). bad for any circuitry. The bad news is this is likely to happen to any metal-based thermometer. It’s probably fine to use a conventional thermometer with blue or red readings that go up/down on a scale (based on alcohol or similar liquid). It is most likely NOT fine to use an old thermometer with silver-colored reading. This is using mercury in liquid state, highly conductive. I’m not sure if it is magnetic – but if it is you can expect the mercury to boil instantly and blow through the thermometer, leaving a dangerous toxic mess in your kitchen. Be warned 🙂

  2. cool car guy

    I loved reading the article, you totally knocked it out of the ballpark! I will keep it in mind for the future.

  3. poor student

    I loved reading this blog, you have a wonderful writing style! I have forwarded a link to my dad, and shall surely be back for more.

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