Induction cooktops, temperature control questions

Somewhere there's a frequency converter that's not 100% efficient, and the induction coils will get hot too.

I didn't suggest poor thermal coupling. Quite the opposite.

Having had experience with natural gas, induction, spiral electric and solid electric hobs, the thermal contact of the latter two with the bottom of a pan is /never/ good.

Kettle, yes they can be efficient since the element is (or can be) in the liquid.

Yes, resistive heating sends lots of heat to other places.

Yeah well you gotta transfer heat from R to thing (beer/ mash in this case.) I could see that my cast iron skillet on induction heater could be better than skillet on resistive heating element. My pan becomes the resistor. (I mostly want to run my stove on low.)

George H.

George H.

Sort of like the Ikea engineers who built a wooden "nightstand" that's exactly 6 rack units high and 19" wide

The reason is probably coil whine. We've got a pretty good one (we cook a lot) and it tunes the coil/frequency depending on the kettle. Sometimes you can hear the whine, but moving the pan/kettle a little bit gets rid of that.

Loud whine close to your hearing range or even above that may manifest itself as headache or strange feeling. I'd bet it's not the EM field.

..

How is the temperature measured on those ? It might be the difficulty of doing accurate temperature sensing with the ceramic plate in between. IIRC some InGaAs photodiodes list this as one application in their datasheets, but I would not expect to see those in cheaper units!

Do they still make it?

Cheers

Phil Hobbs

If that were true you would have one hell of a time in an MRI scanner or near any of our faster mass spectrometers. The laminated core squeals when the magnetic field is being swept quickly and you need earplugs!

It is fairly alarming listening to one squeal and ping from outside the room and loud enough inside to damage unprotected hearing.

I used to wipe my bank cards magnetic stripe fairy regularly when I worked with high power magnetic fields. Great effort was made to obtain maximum uniformity in the beam path but at the expense of more than a little stray field. Modern kit is much better magnetically shielded.

Maybe it is ultrasound? I don't like staying close to ultrasonic cleaners when they are running.

I think maybe that the thing you see when you google "lackrack".

Looks like they may have discontinued the particular model I've used before, unfortunately, this one:

Two Middle Atlantic 6U rack rails and 5 min with a cordless drill and some self-tapping wood screws and it was BYDU!

It does, although when I cup my hands around the bottom of the pot it's not all that much. The main thing is that one can buy 1800W induction cooktops but the small coil burners are never much more than 1000W. I also can't goose those with a step-up transformer because at full bore there aleady is a noticable red glow.

The other thing is the thermal coupling. It takes some finagling with folded paper snippets used as shims to get the coil of both burners to snug the bottom of the pot. I marked them so I know where they go for the "initial coarse alignment".

My favorite heating method is what I do for cooking, a big old fire from a small pile of manzanita or almond wood. I only cook two out of seven days per week but always outside. Rain, shine, hail, sleet, wind, howling storms, doesn't matter. There have been times where I had to tie the barbecue to a pillar near the main entrance and secure the lid with strong wire, so things don't get blown down the driveway.

Do you do FTMS? I have stories. And a nice controller design that probably will never be sold.

The laminated core squeals

There was a conference room at Varian that had a daisy chain of paper clips touching one wall and extending in mid-air out into the room.

From what I saw so far in tear-downs there is a thermistor wadded into something, right under the ceramic plate in the middle of the coil. Probably a PTC or NTC resistor.

It may not be too accurate but brewers soon get a good feel for correction factors. The bi-metal thermostats on my cheap coil burners should theoretically be much less accurate because they only sense the temperature at the end of the heating coil, not the surface. Yet I was able to mark them so I can set them to 156F (for grain steeping) and later shortly under max but outside the numbered range for "boil-over avoidance". Holds it to within +/-2F. Inside the house it is always accurate, outside during summer I have to apply a minor correction factor if it is under 70F, windy or foggy. After a few dozen brews outside one knows. So while the grains of the first batch of the day are steeping I can take a shower and brush my teeth, knowing that the temperature is going to be fine. It always was.

Bricks, then an aluminum plate with big MIL resistors bolted to the bottom. Gap-pad stuff stuck to the top, with the pot sitting on that. Dunk a thermocouple into the brew. Design a controller or buy a cheap Omega equivalent.

Send me a case in gratitude.

add some help,

Was there an adjacent collection of skeletons with stainless steel inserts?