IR gun where to measure?

[Corriewf]

May seem like a silly question, but I just got a IR gun in the mail today. Where do I measure on the woodstove? It is an insert so it makes it a tad harder to find a good spot. The Rutland I have now is in the top right corner. When I measure those corners or the sides I get a very low reading of 200 or so. When I measure on the glass I get over 400. With the IR gun is the glass the right place to measure?

 

[par0thead151]

i too have an insert.
i measure in a corner inside the box, and more often on the stove top. i aim for the iron that is directly above the door but not too close so as to have a lower reading because of the blower.
you can get a magnetic thermometer and place it on the door, thats where i have mine. it may read a little cooler than on a stove top, but most inserts have blowers so we need to make do.

 

[Corriewf]

i too have an insert.
i measure in a corner inside the box, and more often on the stove top. i aim for the iron that is directly above the door but not too close so as to have a lower reading because of the blower.
you can get a magnetic thermometer and place it on the door, thats where i have mine. it may read a little cooler than on a stove top, but most inserts have blowers so we need to make do.

Well I get 600 on the glass right now and 400 just above the door. What is the measurement for overfire? For exmaple if I get 1000 on the glass and 600 on the metal itself, one would be overfiring and one would be great for heat.

 

[par0thead151]

i too have an insert.
i measure in a corner inside the box, and more often on the stove top. i aim for the iron that is directly above the door but not too close so as to have a lower reading because of the blower.
you can get a magnetic thermometer and place it on the door, thats where i have mine. it may read a little cooler than on a stove top, but most inserts have blowers so we need to make do.

Well I get 600 on the glass right now and 400 just above the door. What is the measurement for overfire? For exmaple if I get 1000 on the glass and 600 on the metal itself, one would be overfiring and one would be great for heat.

600 is not really over firing.
lots of folks on here like to cruise at 500-600.
i myself try to get my insert as hot as possible. it is damn near impossible to over fire my unit. might be my wood, but the manufacturer said to just not make anything glow red and i am ok.
i have never gotten the magnetic thermometer to the over fire zone on the gauge, i usually am in the lower 1/4 to top 3/4 range for the "burn zone" on the magnetic thermometer
i would say 500-600 is a great range to shoot for.


if you are getting 1000 on the glass, you have reason to be concerned as the glass is not rated for that temp.
i believe it is lower than a stoves rating because of the airwash cooling it.

and what kind of post is this without pictures of the stove ;-)

 

[Corriewf]

i too have an insert.
i measure in a corner inside the box, and more often on the stove top. i aim for the iron that is directly above the door but not too close so as to have a lower reading because of the blower.
you can get a magnetic thermometer and place it on the door, thats where i have mine. it may read a little cooler than on a stove top, but most inserts have blowers so we need to make do.

Well I get 600 on the glass right now and 400 just above the door. What is the measurement for overfire? For exmaple if I get 1000 on the glass and 600 on the metal itself, one would be overfiring and one would be great for heat.

600 is not really over firing.
lots of folks on here like to cruise at 500-600.
i myself try to get my insert as hot as possible. it is damn near impossible to over fire my unit. might be my wood, but the manufacturer said to just not make anything glow red and i am ok.
i have never gotten the magnetic thermometer to the over fire zone on the gauge, i usually am in the lower 1/4 to top 3/4 range for the "burn zone" on the magnetic thermometer
i would say 500-600 is a great range to shoot for.


if you are getting 1000 on the glass, you have reason to be concerned as the glass is not rated for that temp.
i believe it is lower than a stoves rating because of the airwash cooling it.

and what kind of post is this without pictures of the stove ;-)

I never get close to any of those temp...Was just an example. Seems ike most of the time I run around 450..

This is my stove: https://www.hearth.com/econtent/index.php/forums/viewthread/47171/ with pics.

 

[stanleyjohn]

When i shoot the IR thru the glass i usally get temps from 450 to as hot as 600.Since i have a downdraft type of stove the hot spot of my stove would be in the back afterburn chamber.By the way! Nice stove corriewf :coolsmile:

 

[Corriewf]

When i shoot the IR thru the glass i usally get temps from 450 to as hot as 600.Since i have a downdraft type of stove the hot spot of my stove would be in the back afterburn chamber.By the way! Nice stove corriewf :coolsmile:

Thanks! It's a cheapo stove but it gets the job done. So are you temps on the glass more accurate for what your stove is running then? What is a down draft stove?

 

[zr2yz125]

When i shoot the IR thru the glass i usally get temps from 450 to as hot as 600.:

The IR gun cannot see thru the glass like people can. What it is doing is measuring the energy emitted by the glass, which will be lower than painted steel. You need to set the emissivity value of the material you are measuring for it to be accurate. If your IR gun did not come with an instruction book I can post the calibration procedure for determining "e" value

 

[Corriewf]

When i shoot the IR thru the glass i usally get temps from 450 to as hot as 600.:

The IR gun cannot see thru the glass like people can. What it is doing is measuring the energy emitted by the glass, which will be lower than painted steel. You need to set the emissivity value of the material you are measuring for it to be accurate. If your IR gun did not come with an instruction book I can post the calibration procedure for determining "e" value

If you could please. I have no idea how to do that.

 

[Battenkiller]

The IR gun cannot see thru the glass like people can. What it is doing is measuring the energy emitted by the glass, which will be lower than painted steel. You need to set the emissivity value of the material you are measuring for it to be accurate.

The glass is an excellent spot to take a reading.

Most consumer grade IRs are calibrated for an emissivity of .95 (1.0 being a perfect black body). Most glass has an emissivity very close to .95, and I believe stove glass is no exception. Close enough for country, anyway.

If you doubt that the IR is only reading the surface of the glass, try taking a reading of the inside of your freezer through a warm drinking glass. Yes, the laser shines right through the glass and points at a spot inside the box, but that is not unlike the laser sight on a rifle. It's not about what comes out of the sight, it's about what comes out of the barrel.

 

[Corriewf]

The IR gun cannot see thru the glass like people can. What it is doing is measuring the energy emitted by the glass, which will be lower than painted steel. You need to set the emissivity value of the material you are measuring for it to be accurate.

The glass is an excellent spot to take a reading.

Most consumer grade IRs are calibrated for an emissivity of .95 (1.0 being a perfect black body). Most glass has an emissivity very close to .95, and I believe stove glass is no exception. Close enough for country, anyway.

If you doubt that the IR is only reading the surface of the glass, try taking a reading of the inside of your freezer through a warm drinking glass. Yes, the laser shines right through the glass and points at a spot inside the box, but that is not unlike the laser sight on a rifle. It's not about what comes out of the sight, it's about what comes out of the barrel.

I really appreciate that insight. So if I get 700 on the glass and 450 on the corner of the metal, what would you say the temp of the stove is?

 

[Battenkiller]

So if I get 700 on the glass and 450 on the corner of the metal, what would you say the temp of the stove is?

Ha! Good question.

There will always be hot spots on a stove's surface. Are they the "true temperature"? Not to my thinking. My hot spots move around, from one burn to another and as the load shifts and new flame paths develop during a single burn.

My IR has an "averaging" function that allows me keep the trigger depressed and take continual readings at about 2/second. If I make a reasonable effort to scan in a rough grid-like fashion, I can get the average temp of each plate in about 15 seconds. That info tells me exactly how much radiant energy is being emitted by the entire stove, which gives me a real good idea of how the burn is going inside. My stove has no glass, so other than going by feel, this is as good as it gets.

Often while I am doing a scan of a plate, I will get readings as low as 350º and as high as 850º (OK... I hit 1002ºF in a spot on the left door once, but let's not go there), but the average of the plate will be around 650º. If I can keep the whole stove averaging around 550-650ºF, I feel that I am getting as hot a burn as I dare go to. So far with this new stove, that usually correlates to a single wall flue pipe temp of around 350-400ºF 18" up from the collar after about one hour into a good burn.

Does this answer your question? No, of course not. The real answer is to sit down with a beer (a single malt in my case) and shoot that laser beam all over the place and start to mentally map out your stove's heat zones. Look for spots of consistency (stove top is pretty good for a free-standing stove) and use those spots as reference points for your burns, taking very much into consideration what the fire looks like through the glass and what it feels like in the room. That's the way I do it at any rate.

 

[Lowell]

How far away from stove/glass should you be when taking temps using IR? I've checking mine within 24 inches. Is this OK? Thanks

 

[Battenkiller]

How far away from stove/glass should you be when taking temps using IR? I've checking mine within 24 inches. Is this OK? Thanks

Every IR has a specified D:S (distance to spot) ratio. Some of the cheaper units have a fairly wide-angled detection cone, with something like a 6:1 ratio. That means that at a distance of 24" the spot you are measuring is actually 4" across rather than the size of the little red laser dot we assume it is reading. From the recliner 8' away, that spot is now 16" across - hardly pinpoint accuracy. So the closer you get, the better the accuracy of the reading becomes.

At a certain distance, though, the spot size doesn't get any smaller. The limiting factor here is probably the size of the lens and the internal IR sensor. This info should be available from the manufacturer of your particular unit. I know mine has a D:S ratio of 20:1 and a 1/2" minimum spot size at a distance of 10" and closer.

Another thing to consider is that the laser itself is like a telescopic rifle sight, in that it is offset from the center of the sensor by several millimeters. At extremely close distances, you are better off not using it because the laser beam, being parallel to the sight line of the sensor, is not "sighted in" for short distances.

 

[bokehman]

When i shoot the IR thru the glass i usally get temps from 450 to as hot as 600

Mate, you're not shooting "thru" the glass. That is the temperature of the glass. You can test this to prove the point. Open the door 90º and take another reading so you are looking through the glass into the room. The temperature will be the same until the glass starts to cool from being away from the fire.

the spot you are measuring is actually 4" across rather than the size of the little red laser dot we assume it is reading

A decent one draws out a circle, not a dot.

600 is not really over firing.
lots of folks on here like to cruise at 500-600.

600º is hot for an insert. Don't forget it is being cooled by the airstream so a stand alone stove will be a lot hotter if it had the same fire burning inside. If I load my insert full to the baffle and let it get going, close the primary completely, after about 10 minutes the glass will be at 750-800º. Measured through the centre of the air vent 550º, and top left and right corners of the air vent 500º. SS liner temp around 600º and the collar a bit hotter. At this point the secondary air tubes are glowing and will past the limit of my IR thermometer (1400ºF). Stove stays at that temperature for about an hour and a half. It's impossible to run it hotter. If I open up the primary the temperature drops and the wood lasts less time.

 

[Shari]

We will be in need of an IR gun. It would be helpful if current users of an IR gun would state make/model and possibly a link to where you purchased it.

Thanks much!

Shari

 

[Battenkiller]

We will be in need of an IR gun. It would be helpful if current users of an IR gun would state make/model and possibly a link to where you purchased it.

This is the one I use. It does everything you need and more, plus you can get a fairly tight reading zone from across the room (D:S = 20:1, or a 3" spot at 5' away). Very reasonable price considering the quality - about 1/3 the price of a comparable big name brand.


http://www.instrumart.com/Product.aspx?ProductID=18425


Here's a link to a decent Fluke brand IR gun. Fluke has an excellent reputation for high quality instruments among pros. It's possible it's more durable than mine, but I won't be subjecting mine to much more than home use.


http://www.instrumart.com/Product.aspx?ProductID=19852


My Sixth Sense LT300 has a better D:S ratio and a much better temperature range (goes all the way up to 1400ºF, so you can measure the inside of the box) than the Fluke, and is over $30 cheaper.


I showed you the above units because I'm a fine instrument freak and always try to get the best tool for the purpose. Most folks don't share that trait, so here's one like mine without the temp range or pinpoint accuracy, but it will get the job done at a fraction of the price. Unless you want to really get into the nitty-grity of temp control, this could do the trick for you.


http://www.instrumart.com/Product.aspx?ProductID=10228


My advice is to spend the money and get a good one. It'll piss you off less. The cheapo ones from Northern and Harbor Freight are not worth the bother IMHO.

 

[zr2yz125]

Here is a Thermal image of a glass window in a wide metal frame. You cannot see thru the glass, only the temperature profile of the surface of the glass.

This was taken with a FLIR p65

 

[Battenkiller]

This was taken with a FLIR p65

Yeah, well I have one of those too, but I didn't want to brag.

Very cool photo. I wonder what a whole person looks like.