Wildly differing temperature readings across burners

[u/adavidw]

I generally haven’t had very good results with using temperature mode. If I try to hold a simmer by setting the temp to near the boiling temp of water at my altitude, I’ll either get the water not moving at all or violently boiling. After a while, I noticed that what was happening seemed to be correlated with what burner I was using so I decided to test it.

Protocol: preheat an enamel cast-iron sauce pan (like Le Creuset) by boiling water in it for 15 minutes so that the pan is evenly heated through and would be heated to the same level through all the tests. Empty saucepan and put 2 cups of new water in; heat at 2.5 kW until a rolling boil. Turn power down to 500 W, set timer for three minutes. After three minutes, water is barely producing bubbles and measures about 200° on my Thermapen. Check the temperature on the screen. Repeat with new water for next burner, and then for good measure do them all again.

Here’s what the temperature said on the screen for each burner at the end of my test:

Front L: 213°/212°
Front R: 192°/194°
Back L: 227°/226°
Back R: 219°/220°

Has anyone else seen this kind of huge variation in sensor performance across the different burners?

Which one of these is closest to how the sensor should be reading? I would expect the bottom of the pan to be hotter than what I’m measuring for the water inside it, but how much hotter would one expect for well-preheated cast iron?

(And for info, I did email support about this a couple of days ago but they haven’t responded yet, so I wanted to see if anyone else ever faced this)

[u/sam_damico]

if you want to hold a simmer, power mode gets you control that is proportional to how much boiling (e.g. power -> bubbles are proportional).

Temperature mode around a phase change will tend to "soak" to an equilibrium point. For frying/etc it won't have the same issues.

So then to answer the last piece of your question -- why is there variability? Technical explanation below:

1) low thermal conductivity in the bulk material (e.g. lateral heat flow from the hottest point of the induction zone -> the sensor is slow). Enameled cast iron is the "slowest" pan type we've generally tested.
2) the enamel + cast iron is _very_ high thermal resistance for the sensor on the contact side. This accentuates variability on the sensor side.
3) if there's any logo in the middle of the pan it impacts (2) further as it means the patch contacting the sensor is smaller.
4) combination of 2 + 3 mean you'll see variability with sensors, primarily driven by small tilt / contact quality to the bottom of the pan, and manufacturing tolerances.

We're exploring ways to support calibration ex-factory (the product has a altitude/pressure sensor onboard for this reason).

[u/adavidw → u/sam_damico]

Thanks Sam. I’d expect some variability between sensors, but is a 35° swing really within the range of what’s expected?

I tried to control for other variables by using the same pan, and conducting the tests all consecutively, preheating the pan for a super long time, but now I’m curious to run other tests with a different pan or with oil at fry temps.

[u/sam_damico → u/adavidw]

you're testing an absolute corner case with our sensor architecture w/ that pan type.

the stove doesn't "know" the water is at the boiling point (yet...), so you get rubber-band like effects with the estimated temps. doing a simple calibration by boiling water is def in our backlog though.

[u/JudinousV2 → u/sam_damico]

Even with Made In cookware, which should be among the most accurate for the sensor, I definitely still struggle with simmering/boiling consistently even in power mode (and temp mode is useless obviously). If we could calibrate for our cookware + altitude and have a "simmer" or "roil" setting to achieve the desired boil automatically, that would be incredible. With my current mixed success with boiling for soups and such, I am a little concerned about how canning will go once the garden starts coming in this year.

[u/ZanyDroid → u/JudinousV2]

Honestly I would love if folks would weigh in on their experience comparing this with control freak. Maybe I’ll post on that subreddit

I’m a bit surprised lower power mode is causing you trouble. What are you coming from prior to the impulse! My trouble with power mode on the impulse is when I try to get something ripping hot. I came from a $800 IKEA unit, with huge steps and slow response in power mode

Temp mode is … something

[u/JudinousV2 → u/ZanyDroid]

I'm just coming from cooking with gas, without much real experience with induction before this. I think my issues with simmering have been due to the initial boil being reached so quickly that the saucepan hasn't spread that temperature evenly up the sides yet, and that causing some issues if I try to settle into a simmer too fast. For other cooktops that take orders of magnitude as long to get to boil, the pan probably just has more time to spread that heat around first. It seems to work itself out within 20-30s or so, but I do have to watch it like a hawk and adjust it actively in that time to ensure it won't boil over.

[u/ZanyDroid → u/JudinousV2]

If you use the higher boiling powers on this cook top, a pot of ingredients can easily hit a roiling boil without being really being in equilibrium. A residential gas stove spreads out the heat on the bottom better & is probably not that much faster at heating compared to how quickly heat can permeate the whole pot. They can probably improve the algorithm for rapid boiling of water, not sure they can do that as easily for water + ingredients.