Dome gauge wayyyyy off.


 
P

Paul Pearson

TVWBB Super Fan
I was cooking a chicken last night on the 18.5 and thought I would just check the gauge to the thermapen. I was running 300F according to the dome gauge and when I stuck the thermapen in the vent for a few minutes it settled in around 389F.

That was the first time I had checked it at that high of temp and I was surprised how far off it was. I have an extra lid vent, could the exhaust flow be that much hotter than the more stagnant part of the dome?
 
I have just done a similar experiment.

I had been taking temps through the lid exhaust and found almost 50F difference between the dial and probe. Thinking that the dial is out of calibration as you keep reading about them online, I went on the probe temp. Just fired up the WSM and got it to temp on the dial. Removed the dial from the lid and placed it in a pan of boiling water. 212F/100C reading!!! Placed the probe in the water - 212F/100C!!! Done the same with the handheld probes, and all read 212F/100C!!!!

For the 2nd part of the experiment I used a piece of thin wire to attach the remote probe to the dial probe in the lid and monitored the temps. Dial was saying 235F but the remote probe was saying 260F!!! Both read identical temp in the boiling water not 10 minutes earlier !!! I made sure that the end of the probes were equally aligned in the lid.

The only explanation I can think of is that the cable on the remote probe is picking up a higher temp from inside the lid as obviously the wire wasn't placed in the water.

Very strange indeed but at least I know that the dial thermometer is a lot more accurate than I thought it was.
 
It makes me wonder if the reading is increasingly off with higher temps or if the dome and exhaust temp are not the same. Since I have 2 lid vents I have a lot more air movement now compared to stock.
 
Paul Pearson said:
It makes me wonder if the reading is increasingly off with higher temps or if the dome and exhaust temp are not the same. Since I have 2 lid vents I have a lot more air movement now compared to stock.
Click to expand...

Have you removed the dial thermometer & done the boiling water test with it? It does sound like a virtually identical scenario that I was having until today's experiment proved my initial thoughts wrong.

One option that I might try for the higher temperatures is to put the deep fat frier on and probe the oil against the dial and see how it is on the higher range.

Might be worth closing one of the lid vents fully, but even then probing through it would give higher temps than the dial as explained by others.
 
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