Thermocouple Accuracy (or lack thereof)

[douglasbialor]

I've somehow acquired quite a few different probes of various types and am having trouble getting any of them to agree with each other. I've got a Thermoworks armored cable probe, another metal probe that came with an Auber controller, and a couple of the naked end ones for monitoring air temp in the cooker. They'll mostly agree with each other within a degree or two at ambient air temps of 65 degree and I've done the boiling water test and they are showing anywhere from 206 to 213 degrees, but then I put them in a WSM and I'll get a range from 310 to 375 degrees from 3 or 4 different probes. Seems like 5 or 10 degrees would be a large but still reasonable amount of disagreement, but 50 or 60 degrees is way too much and it doesn't seem as if it's just one particular probe that is out of range.

Wondering if anyone has any ideas of what may be going on here or is this just the nature of these types of probes? I've read that accuracy is supposed to be within about 2 deg celsius.

Thanks,
Doug

[Spinaker]

douglasbialor The only thing that I can think of would be, that your getting moisture on the probes or inside of the probes themselves from the humidity inside the cooker. Or depending on the food, fire or the combination of the two, you may have hot and cool spots developing inside the cooker. Those are the only things that I can think of.
Good Luck

-John

[Jon Solberg]

Hey Doug, Welcome to the pit. If your probes are right in boiling water (or close) than their right.

​Are you putting all the probes in the WSM at the same point? I experienced big temp variations in a WSM. It takes hours to balance it out.

As an example My WSM top grate is normally 30°- 40° different than the bottom. Its also always much hotter at the wall over the "gap" then the center of rack. I call the gap the open space between the water pan and wall. This is true no matter which rack you set on.

The heat inside that thing is not as even as I thought it was for sure. Ive spent a lot of time testing probes thinking there just no way that they could be right inside that bullet. Its odd.

[douglasbialor]

Thanks, Guys. I do have the probes all in the same spot, within an inch or so of each other right above the grate. I think I need to start over with the boiling water test and make sure they are all really testing at out the 212 degree mark and go from there. Wondering if a few degree difference at 212 becomes a larger 20 or 30 degree discrepancy at 350 degrees.

Thanks!

[Meathead]

Probes do go bad. Industry standard on K type probes is that they can be off by about +-2F, but the better ones should be spot on.

[mgaretz]

A way to test at high temps, say 300-350f, would be to use oil instead of water. Heat some on the stovetop in a large Dutch oven - the oil temp should be fairly constant throughout. But be very careful with the hot oil! Make some fried food when you are done so as not to waste the oil!