How do I know my probes are accurate?


 

JeffLa

TVWBB Member
Hi,

I am trying out my newly built HeaterMeter today (Christmas). I am not using it yet to control a damper or a fan. Only to watch the temperatures of the grill and meat. I am also using a dual probe wireless thermometer sold by Big Green Egg to compare readings. I purchased a few different probes for the HeaterMeter so I have two different probes measuring the Pit temperature. One is a Thermocouple probe that I got on Amazon here:

https://www.amazon.com/exec/obidos/ASIN/B0142RXG84/tvwb-20

The other is compatible with Maveric ET-73 bought on jet.com here: https://jet.com/product/6-Foot-Meat...-Probe-Only-/0c5dc94d171841b59f458de23243fab2

Unfortunately I am getting three very different readings. My Big Green Egg Wireless thermometer says the pit is 239F, the Thermocouple says 207F and the Maveric ET-73 compatible probe says 183F.

In the HeaterMeter configuration, I have the maverick ET-73 compatible probe configuration using the preset values for Maverick ET-72/72 and the Thermocouple probe set to 5 MV/C with no offset (this was default).

My Big Green Egg lid thermometer says 250.

I have no idea who to believe! How do I get these probes calibrated properly?

Jeff
 
Temps can very alot in different places. The lid temp is probably not the best to use, as it will be hotter then the grate temp. If your probes are in different places, then they could all be correct, except maybe the Et-73 probe, that one may be no good.

But, you can wrap them all together in aluminum foil and place them on the grate at the center and see if they have the same temp.

Boiling water is the best test. The offset shouldn't be used
 
Thanks for the info. It turns out that the Thermocouple probe eventually agreed with my Big Green Egg Wireless thermometer probe. The ET-73 just looks to be off. I also noticed that the Thermocouple probe is MUCH slower than the Big Green Egg Wireless thermometer probe. It just took a long time to reach the accurate temp.
 
The thermocouple shouldn't take very long, unless you have a fairly cheap one or its not the right type for bbq, . Everytime I do a boiling test the probes and thermocouple go up about the same rate.
 
OK I confirmed that the standard probes all agree within a reasonable tolerance. The Thermocouple probe is almost 8 degrees F off from the others. Is this definitely a Thermocouple problem or do I need to tune something on the circuit?

Thanks,

Jeff
 
OK I confirmed that the standard probes all agree within a reasonable tolerance. The Thermocouple probe is almost 8 degrees F off from the others. Is this definitely a Thermocouple problem or do I need to tune something on the circuit?

Thanks,

Jeff

Is the thermocouple reading high or low in a boil test?
 
I don't want to sound all negative, but it looks like you shopped around for the cheapest probes and thermocouple you could find and now expect them to be scientifically accurate. I suggest you do the boil test, and a room temp test. I would also suggest that if you want accurate probes that you spend a little more money and buy better probes from a known manufacture. I buy all my probes (now) from Thermoworks. I tried the "buy cheaper" method for probes and was disappointed.

Honestly though, this is BBQ, not rocket science. When doing brisket or pulled pork, you should be smoking meat until it is tender, not a set temperature. And it wont matter if your smoker is at 225 or 240. You only need to worry about temps when you are cooking for food safety, and then do you want to gamble with food poisoning with the "cheapest" probe you could buy?

Wow, sorry, that got a little ranty.
 
Here's a test with 3 probes in the oven to test for consistency, accuracy, and response. Probes used were a homemade thermocouple, an ET73, and a Thermoworks probe. I found that the TC has the fastest response time, and the ET73 followed closely behind. The Thermoworks probe, although accurate, did not seem to have as fast of a response.

All probes were tested in boiling water (in my case, 203.5 degrees F as I am at 4500 feet altitude) and all were within 0.5 degrees.

xiZj4tR.jpg
 
I don't want to sound all negative, but it looks like you shopped around for the cheapest probes and thermocouple you could find and now expect them to be scientifically accurate..

No that doesn't look to be the case at all. Maverick probes aren't just some POS probe, and thermocouples (if you know how they are made) are very inexpensive materials assembled in a very simple and reliable way.
 
No that doesn't look to be the case at all. Maverick probes aren't just some POS probe, and thermocouples (if you know how they are made) are very inexpensive materials assembled in a very simple and reliable way.

I also agree.

What you buy, when getting a more expensive TC is quality. The cheaper probes will work just as good as an expensive one, but won't hold up as long. If the wire used is not made for high heat then it's only a matter of time before it's melted, that one of my issues with Auberins.com TC'S.

WBegg

The response time is related to the thickness of the probe. A thinner probe will have a faster response, then a thicker one. I have a TC that is plain wire and it's response is to much, and makes for a terrible Tc. You don't want a TC that's super fast, it would only cause problems with controlling the smoker or bbq.
 
What you buy, when getting a more expensive TC is quality. The cheaper probes will work just as good as an expensive one, but won't hold up as long. If the wire used is not made for high heat then it's only a matter of time before it's melted, that one of my issues with Auberins.com TC'S.

Even at that, what do you need for a TC? Two (metal specific) wires welded together at one end with a shielding running the length of the wire, and the yellow plastic injection molded plug and that's it! It can be difficult to skimp on those materials and build quality.


I have a TC that is plain wire and it's response is to much, and makes for a terrible Tc. You don't want a TC that's super fast, it would only cause problems with controlling the smoker or bbq.

I had one of those too, had no shield on the end - just the bead showing. Crazy fast response, and not so great to work with. I always advise people when they go to buy a thermocouple to make sure they have one with a shield, because the exposed bead (which is just the solder joint) will react too fast and can make PID tuning a little messy. It's nice to have something a little slower.
 
Last edited:
The response time is related to the thickness of the probe. A thinner probe will have a faster response, then a thicker one. I have a TC that is plain wire and it's response is to much, and makes for a terrible Tc. You don't want a TC that's super fast, it would only cause problems with controlling the smoker or bbq.

I also completely agree. This is why the TCs I make have a 4mm SS sleeve (tube) on the end. I was just demonstrating that the response time is acceptable. I've used some TCs that had so much lag in response (ones with the huge sleeve), that they were unuseable.
 

 

Back
Top