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Author Topic: IR Thermometers  (Read 16588 times)
McRoots
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« on: November 23, 2015, 04:01:12 PM »

I just got the private sale email from Thermoworks.   Been wanting to pick one up and the deals are good. 

Does anyone have one that they would recommend?
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McRoots
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« Reply #1 on: November 23, 2015, 05:24:15 PM »

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BBQRich
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« Reply #2 on: November 24, 2015, 06:53:42 AM »

I have the $33 model - high temp range, great for pizza stone / steel temps.
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McRoots
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« Reply #3 on: November 24, 2015, 06:40:16 PM »

Thanks for the recommendation.  I ordered one.  Looking to just that... Take the temp of pizza stones / baking steel.
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Cajunate
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« Reply #4 on: November 24, 2015, 08:32:31 PM »

Costco had one they were selling with a free stud finder. EVERY time I went down that isle all of those packages would go berserk!  Grin
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bubbagump
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« Reply #5 on: November 28, 2015, 07:41:18 AM »

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McRoots
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« Reply #6 on: December 20, 2015, 05:27:38 AM »

This proved useful last night.  Cooked my first pie since I got this thing.

Used it to check the temp of the pizza stone and the actual dome temp.  Learned that it takes a long time for them to equalize.  I also learned that the dome thermostat wasn't even close to showing the same temp. 

No wonder I've I had some issues grilling lately (chicken taking forever to reach 165).
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Dragonfly
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« Reply #7 on: December 20, 2015, 11:03:46 AM »

I have an industrial IR thermometer from Thermoworks (not sure if same as model shown), and I find it to be useless.

To get an accurate reading, you have to adjust the setting (emissivity?), to the material being measured.  That means, one setting will not work for the dome, the stone, the Keg exterior, etc.  There are guidelines with a lot of potential settings.  Four settings for steel, 10 settings for paint, etc.  Two and a half pages of suggested settings for various materials.

In other words, the temperature reported is a function of whether your setting is accurate, and I believe I found it to be so different (say, among the various steel settings), as to be useless.  I almost never use it as a result, nor have I bought a cheaper one with no adjustments, because I suspect they all work the same way and those must be inaccurate across various materials.  

When I do use it, I attach the probe and use the probe, which does not depend on the emissivity setting.  That was the advice Thermoworks gave me.  If you want to use IR, they say to set emissivity, take temp.  Insert probe, take temp.  Adjust emissivity until temp matches the probe, and then you have the right setting for that specific material.  Hard to do in a hot Keg, or on something ten feet away (like in the attic).

I seem to recall there is an upper temp limit as well, and if you point it at the fire (come on, we all do), it can make future measurements inaccurate.
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78 T140E
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« Reply #8 on: December 20, 2015, 01:24:42 PM »

I purchased a Nubee NUB8550H from Amazon several months ago.  It also has an adjustable emissivity setting for different materials.  The brief manual has a table of emissivity settings for 48 different materials.  Most (but not all) common materials have an emissivity of or very close to 0.95.  The default setting is 0.95, so most materials won't need a setting change for relatively accurate readings IMO.  The temperature accuracy from 212°F to 932°F is ±1.5%.  As BBQRich said it works great on a ceramic pizza stone and the Broil King Grilling Steel without changing the setting.

BUT, shiny or polished metal surfaces (for example, stainless steel or aluminum) have a significantly lower emissivity which will require a setting change for an accurate reading.  Gold, polished aluminum and polished brass have very a low emissivity of 0.01 - 0.10.  I'd guess that stainless steel would be similar.  Also, the specifications did not say how much the temperature reading was affected by an incorrect emissivity setting - they just say 'inaccurate'.

And, one last thing - steam, dust and smog (smoke) will lower the accuracy of the reading.
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McRoots
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« Reply #9 on: December 20, 2015, 06:38:37 PM »

Interesting.  In the past, the pie went on when the dome thermometer was in the 600 range.  When it got there, I checked the stone.  It's around 250F.  So I wait.  I let the keg creep to 700F (by mistake) over the next 30 mins and check again. The stone is now ~550 and on a whim, I shoot the inside, upper dome. It's within ~20F of the stone.

That's what when I put the pie on and it cooked fairly evenly this time. In this regard, that's the improvement I was looking for in getting the IR gun. 
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Dragonfly
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« Reply #10 on: December 20, 2015, 07:54:33 PM »

Interesting, T78.  The Thermoworks table has 125 materials.  Works on ceramic pizza stone and grilling steel?  The setting for clay, fired is .91 (tile is similar).  The highest setting for steel is .59 (some are in the .20s).  Less than half the settings in the table are in the .90s.  Thermoworks says the emissivity varies with temperature and texture as well, so the settings are just estimates.  (Some materials like plywood have a range of ~15 points).  Perhaps a dark grilling steel is similar - I don't recall trying it.

It has been a few years, and cooking was not my primary reason for getting the thermometer - but I got really wonky readings when measuring things using the default setting, which is why I called Thermoworks and found out about adjusting emissivity and they pointed me to the table online.

Makes me want to try the probe and see what settings match the probe results and how that compares to the table, but not sure I want to spend the time. I probably ought to just to decide whether to keep it or get rid of it.
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Dragonfly
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« Reply #11 on: December 20, 2015, 08:19:56 PM »

Before putting it up, I tried a few things on the .95 setting.  It was pretty accurate for dark granite, our painted wall, butcher block, a brushed stainless surface.  The Keg exterior was off by 4 degrees, at 64 degrees.  Pretty big difference.  The probe takes some time to settle, not instant or near instant so challenging to hold in a hot environment.
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kite
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« Reply #12 on: June 07, 2016, 05:28:39 PM »

Since I am reading old posts and I have some experience with IR thermometers I'll add some info here. Yes IR guns are effected by different objects. Overly simply the reflectance of objects change the reading. Generally units are calibrated for reflectance of brown paper. Metals tend to higher than organics. Paints often have metal in them and can vary quite a lot. The other thing that can happen is shiny objects (aluminum foil for example) cause the reading to reflect away and create a massively inaccurate reading. I have seen 30-40ºF off. They also cannot accurately measure in hazy conditions trying to measure a very smokey smoker likely you would only get readings off the smoke itself.

The DS (distance to spot) ratio is also important, 1:1 means the measuring circle is equal to the distance. IE at 12 inches it would be reading a 12 inch area. 10:1 is the reading area is one tenth the distance so at 12 inches 1.2 inches. Add to complication each DS range has optimal usage distances, again very generally the 'focus' distance of the lens (fresnel)
1:1 best distance is under 4"
6:1 Best distance is under 24"
12:1 best distance is under 48"
20:1 best distance is under 80"
50:1 best distance is under 200"

The end of the day the user needs to have some understanding of the instrument. IR guns are fast allow for non contact. They are not the most accurate of tools. There is some play up and down.

Tips. Measure, move, measure again, changing angles can help with reflective objects if you get really different, you know to check again. Keep in mind DS ratio averaging hot coals and cool pizza stone will not work well. Look up the error rate and live inside it. Personally I figure that the correct temp is in ten º window, 5ºF up and or down from the displayed. If you must have better double check with a good direct reading thermometer. Averaging is a great feature, one of mine has an average feature and I can 'sweep' a surface and get an average of multiple readings.

The last tip is batteries, for some stupid reason sometimes manufacturers use a silly battery, before you buy check that the battery is not something exotic. I have an old one with a thermocouple input (and a on/off switch because of it) that takes two CR123a batteries. Where I live off the shelf (if you can find them) they are 14$ each. Needless to say leaving it on causes much cursing and it moving up on a shelf in a box.
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Alex
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Re:
« Reply #13 on: June 10, 2016, 02:46:14 AM »

I don't use one.
Interesting about all the details that you need to know.
In a keg there is a 50 difference at grate vs the dome.
You can cook something at 230 or say 300, it will come out almost the same.
Did you cook anything in you new keg?

Sent from my Nexus 6 using Tapatalk
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