How to calibrate the different types of probes?

Tim Loftus

New member
this is my main pit probe: Auber K Type Thermocouple w/ alligator clip (link at the bottom.
for fun I picked up this along with two meat probes Thermoworks Pro-Series® High Temp Air Probe With Grate Clip
what do you use to calibrate these probes? (I know how to do it in the HM software) I am just not sure if the ice bucket method, boiling water, or oven would be best. I have used the auber for years and am on my 3rd or 4th one. it seems like I have to clean the tip after every smoke otherwise I don't get consistent readings. the last couple of smokes I have added the thermo air probe and it is reading vastly different then the auber. (although, now that I am typing this out) port 1 on the HM might be set for one of the meat probes and that might be part of the issue)


also is there any high temp - food safe heat shrink tubing for these braided probes? The Auber especially had tons of "hairs" that poke out and are a PITA. I figure some heat shrink tubing would fix that, maybe not on mine now but on a new one it might prevent it from happening.


Auber Alligator clip - https://www.auberins.com/index.php?main_page=product_info&cPath=20_3&products_id=172
Thermoworks Air Probe - https://www.thermoworks.com/TX-1003X-AP?tw=VWB&chan=TVWBB
Thermoworks Meat probe Straight - https://www.thermoworks.com/TX-1004X-SP?tw=VWB&chan=TVWBB
Thermoworks Meat probe curved - https://www.thermoworks.com/TX-1001X-OP?tw=VWB&chan=TVWBB
 

Bryan Mayland

TVWBB Honor Circle
You should just be able to set them to the proper type in the configuration interface and that's all there is to it. The numbers don't line up the same between different probe models and types usually though. For example, that same Auber Type K with alligator clip is low by about 3 degrees from my Thermoworks Air Probe. The same is true with this Hi-Temp 12" Industrial Probe from Thermoworks. Others have reported that their thermocouple is slightly higher by a couple of degrees. Our ProSeries settings come from a user who used a certified calibration device to fit the probe response (since Thermoworks does not provide the actual specs) so they may be further off at some temperatures versus the others.

If you find that the probes diverge in a linear fashion as the temperatures change, you can adjust the mv/C in the configuration to adjust the linearity of the thermocouple. If they're off by a small fixed amount across the entire range, use an offset to adjust one or the other. Note that if your offset is more than just a few degrees then something else is wrong somewhere. If you find them to be all over the place, then you can do your own correlation and enter your own custom probe coefficients. There's a module in the linkmeter daemon that assists with this, but it is an involved process of running through a thousand different temperatures with the two probes as tightly thermally coupled as possible and does a least squares fit to generate new coefficients through the range you run the calibration on. I've only used it three times but the lmclient command is LMUP:
LMUP,start - start the process. Probe 0 is the reference probe, and Probe 1 is the probe to be calibrated
LMUP,csv - to see the current data if you want to make a graph or something
LMUP,fit - to calculate the current custom coefficients given the data so far
LMUP,stop - go back to normal operation (or just reboot)

Have I given you too much information yet? :-D
 

Gary V

TVWBB Member
Good info. Yup my heads a spinning.
My current current Thermowork RTD probes were verified at my former employer in the cal lab and they were close to reading the same. We didn`t check the thermocouple because we thought the silicone oil might be nasty if it dripped on food. It is interesting to see the differences when verifying probes in boiling water. While the calibration pot showed one thing boiling water showed something different. I suspect it was because I could not control water temp like a certified calibration pot. I do hope that users know calibration is also effected by their elevation, so they need to use a chart that reflects this. Since my alligator probe has finally started to get flaky, i will pick up another one. I do have some 260 degree C heat shrink so I will cover the section that is exposed to the smoke and then snake into the grill and reconnect the plug. I Hope this give me more life on pit probe if it is soaking up smoke and grease that could cause thermocouple voltage degradation.
 

WBegg

TVWBB Pro
Good info. Yup my heads a spinning.
My current current Thermowork RTD probes were verified at my former employer in the cal lab and they were close to reading the same. We didn`t check the thermocouple because we thought the silicone oil might be nasty if it dripped on food. It is interesting to see the differences when verifying probes in boiling water. While the calibration pot showed one thing boiling water showed something different. I suspect it was because I could not control water temp like a certified calibration pot. I do hope that users know calibration is also effected by their elevation, so they need to use a chart that reflects this. Since my alligator probe has finally started to get flaky, i will pick up another one. I do have some 260 degree C heat shrink so I will cover the section that is exposed to the smoke and then snake into the grill and reconnect the plug. I Hope this give me more life on pit probe if it is soaking up smoke and grease that could cause thermocouple voltage degradation.
Maybe cover the pit probe end with Kapton tape? This would be easily replaceable.
 

WBegg

TVWBB Pro
Another option is the route I took. I make my own thermocouples. Easy to do. I get tube ends from alliexpress ($16/100) along with k-type braided wire and plugs. Costs around $4 a thermocouple when complete. Just have to have a way to arc the wires together, a battery will work, but I found a used jewelers welder that works a charm. I started by crimping the tube, but now use a high temp cement made for just this purpose. Not cheap, but glues seals the end very well.

 

Bryan Mayland

TVWBB Honor Circle
Oh I forgot about the heatshrink question! They make PTFE (teflon) heatshrink that is heat safe up to like 250C and food safe up to somewhere around that.

WBegg: Those are some great looking probes, like commercial quality there and assembled with 20% more love than any other brand.
 

Gary V

TVWBB Member
Will.
Great looking probes. Looks like it might be time to buy a spool of K-TC cable and make some for how they get used in my grill. I have a few old K-types plugs laying around from old probes, so i got that covered. What type of high temp cement did you use. Also did you pack the tubes with a ceramic filler or just the high temp glue.
 

WBegg

TVWBB Pro
Don't know the brand off hand. It's not cheap, but one tin will do thousands of probes. I do not fill with ceramic filler, but occasionally will wrap a small piece of Kapton around the welded end to prevent shorting to the wire braid (Isolated).
 

BrentM

New member
Don't know the brand off hand. It's not cheap, but one tin will do thousands of probes. I do not fill with ceramic filler, but occasionally will wrap a small piece of Kapton around the welded end to prevent shorting to the wire braid (Isolated).
I learned about the issues surrounding the unintentional grounding of ungrounded thermocouples (the type we have here). I don't mean any disrepsect for Auber instruments, but two of the four k-type thermocouples I purchased from them have TC wire short to the shield.

If you're making your own thermocouples, you should test for this or be aware of it... I thought about testing it as you set the TC wire... then clamping it and allowing to dry.
 
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