Question on probes

[UncleSpike]

I’ve got a Thermoworks Smoke X4, that I’ve had for a few years.
Late last night as I started some briskets, I plugged in the ambient temperature probe and three others for the meat. They were all outside the smoker. I noticed a 30 degree difference between them all. The weird thing was that two of them were at about -3 degrees, and one was at 28 degrees. This threw me off for a bit, as the air temperature was actually -3 Celsius, but they were reading in Fahrenheit. This meant that only one was accurate. Confusing, eh?

Then overnight, the remaining probe was reading 153 degrees. It has now dropped to 135, so I’m afraid it’s no good either.

My question is - what makes them go bad? And how do I really know what’s accurate?

[ItsAllGoneToTheDogs]

All probes eventually fail or at least become less accurate. Test em with ice water every few months or at least before expensive cooks to make sure they are still accurate.

[RichieB]

+1 on the ice test. Another option if you have another thermometer you can compare. I've lost a couple of probes. They're not lasting forever and fortunately not too expensive to replace.

[Alan Brice]

Extremely happy with my Meater+. I am currently watching the posts from Combustion Inc. Fed up with wired probes and the hassle. YMMV

[HawkerXP]

Before throwing them out, try placing the whole probe and cable assembly in a warm (not hot) oven. You may have some moisture that this will dry out.

[RonB]

I'd run the oven at ~ 250° to make sure any moisture in the probes evaporates. If the connectors are not heat proof, leave them out.

[chefchrisyoung]

Those series of probes from Thermoworks use thermistors. Thermistors can be really low-accuracy or really-high accuracy, but high-accuracy requires good calibration and tight tolerances. Thermoworks does a well-above-average job of providing well-calibrated thermistors.

While thermistors will tend to drift a little bit over time with lots of use, but for most real world uses it's usually a non-factor and is often less than 0.1°C.

What can happen—and what I think is going on here—is that some water or meat juice has gotten into the thermistor circuit and is reducing the electrical resistance. Thermistors work by measuring the electrical resistance and converting this into a temperature measurement. If there is a bit of an electrical short that reduces the electrical resistance, the thermistor is going to read as a higher temperature than reality. Drying it out may help, but realistically if the short has happened, it's pretty much useless.

Note, because thermistors are very nonlinear, it might only read a little high in an ice bath, but a lot high at cooking temperatures. Don't assume that if it's off by 5 degrees in an ice bath, that it's only off by 5 degrees at cooking temps.

[fkrall]

I depend on the Thermapen and Smoke and am currently struggling with the meat probe on a newly gifted Traeger. Your last paragraph is worth its weight in gold. Thanks!

[UncleSpike]

I wonder if it's a moisture issue. I know you are not supposed to submerge them, but i usually do - it just makes them easier to clean...

I'll try run some tests tonight. Otherwise I guess we'll just have to shop for new ones...

[ItsAllGoneToTheDogs]

UncleSpike I use the side of my sink to hold the probe against, scrub the probe, turn, scrub, turn etc... quick and easy no submersion required

[UncleSpike]

And while we're at it - can you test the ambient probe in an ice bath and boiling water as well? Or is it not built for that?

[Donw]

I test my ambient probes with no issues. I have a Smoke and a Fireboard.

[Bruceski44]

Note, because thermistors are very nonlinear, it might only read a little high in an ice bath, but a lot high at cooking temperatures. Don't assume that if it's off by 5 degrees in an ice bath, that it's only off by 5 degrees at cooking temps.

Agree! They should also be checked w/boiling water, which will be lower than 212F at high altitudes. With each 500-feet increase in elevation, the boiling point of water is lowered by just under 1 °F. I'm at 2700 feet, therefore the boiling temp here is below 206.6F.

The probe's response should follow a straight line with a slope of 1. The old equation for a line, y=mx+b shows the terms: X is the input (process) temperature, Y is the displayed (indicated) temp, m is the slope (gain) of the line and b is the Y-intercept (offset). The offset can be checked at freezing, and the gain should be checked at boiling. Both gain and offset errors will exist; compensating for only one will still result in measurement error.

[texastweeter]

Test in ice water and boiling water. Replace when inaccurate. If they get wet and are not waterproof they can often be saved by dehydrater set on 140°