Reptile & Amphibian Forums

I know this is specific to the forum but figured I'd get some good responses here so...

I've been keeping a lilttle Petco dial thermometer on my wall and assumed it was at least reasonably accurate. Then very recently I got a Vision rack system, a dimmer switch (don't think I need to spend for a thermostat), and a Harbor Freigth 8:1 infrared temp gun (on sale for $27).

First thing I do with the temp gun is to check it against my Petco dial...~ 10 degrees F difference...so WTF??? Well, seems I need some triangulation here so I picked up a ZooMed digital with probe today...well, wouldn't ya know, it falls right in between the two...so now I'm like really WTF!!!

Any ideas, experience, opinions?

Thanks,
Brad

I am no expert Monklet, but I would assume the little wall mounted thermometer measures more general ambient air conditions than the probe or infrared gun does. I would say the infrared would be better for measuring the temps inside the cage on top the bedding, cage bottom, etc., and not necessarily the ambient temps in the room. The probe is also limited to where its measuring the temps with relationship to its placement. The probes can read higher or lower based on stratification of the air temps in a room from ceiling to floor, or along the top to bottom of a rack. I experienced temps ranging from 86 to 81 degrees in my herp room this past summer. I would rely on the infrared gun and just check the actual cage temps where the animals are to be safe. You can also spot check various areas/surfaces of the room to make sure temps are within acceptable ranges for your purposes. I try to keep my brumation room between 55-60, but dont sweat it if the temps get much lower from time to time as long as above freezing.

Thanks Kevin for the detailed response.

Of course I do understand the difference in the 3 different devices but it seems that if you temp gun the wall thermometer the two temp should be pretty darn close rather 10 degrees F??? I also put the probe right next to the wall thermometer too and it read 5 degrees F. Something tells me the probe, obviously a thermocouple device is most accurate, and it falls right between the other two. The spring tech wall job is cheap and probably the most suspect. The temp gun has no calibration facility as some models do so maybe that is the issue there, e.g., that it was never properly calibrated.

Never the less, as it stands I don't have any confidence in any of them.

Yeah, I hear ya about the confusion with the devices!! I can see where the probe device may be the most accurate for ambient temps, I just dont like the fact it only reflects the level the probe is on. However, I do use a digital probe thermometer in my brumation room is a general temp indicator. The infrared gun is geared towards reading the temps off of surfaces, like engine blocks. IMO, I dont think its really designed to read ambient air temps. I quess if worse comes to worse you can always hang an old fashion mercury yard thermometer in the room to get a general idea what ambient temps are. A good friend of mine that maintains a large collection told me he relies on the digital probe thermometers the most. According to him, they are cheap and reliable, and some models can give you the min and max temps in the room so you can see the fluctuations that occur.

Well, I figured that if I "gun" the wall thermometer it should be pretty darn close to the air temp at the place, providing the air temp is fairly stable which it is.

Just looking this stuff up on Wikipedia.

"The more reflective a material is, the lower its emissivity"

"Emissivity depends on factors such as temperature, emission angle, and wavelength. A typical engineering assumption is to assume that a surface's spectral emissivity and absorptivity do not depend on wavelength, so that the emissivity is a constant. This is known as the "grey body assumption".

Although it is common to discuss the "emissivity of a material" (such as the emissivity of highly polished silver), the emissivity of a material does in general depend on its thickness. The emissivities quoted for materials are for samples of infinite thickness (which, in practice, means samples which are optically thick) — thinner samples of material will have reduced emissivity.

When dealing with non-black surfaces, the deviations from ideal black body behavior are determined by both the geometrical structure and the chemical composition, and follow Kirchhoff's law of thermal radiation: emissivity equals absorptivity (for an object in thermal equilibrium), so that an object that does not absorb all incident light will also emit less radiation than an ideal black body
"

Whew!!!

The infrared thermometers measure emissivity so they need to be calibrated depending on the material to be metered. As I mentioned some infrared thermometers have a calibration adjustment. Mine does not. It is probably assumed that it will be used on fairly standard E=1 materials.

Good suggestion about getting a plain ol' mercury in glass thermometer to get a baseline. They might be hard to find these days though as they are being phased out due to the mercury.

"They might be hard to find these days though as they are being phased out due to the mercury"

I use a few different kinds to get a good "median" idea of what is going on. digital probes, dial thermometer, and red liquid wax thermometer. Also a laser-sighted temp gun for inside on the animals or a surface.

I have pointed this directly at the dial thermometers in the past and got similar readouts, so this way I know it can't be a real practical difference either way. Plus the gun has a quted accuracy of or - 1.8 degrees too, so who knows which is realy more accurate out of all these, they all show varying differences here and there, so what the heck can ya do?..LOL!

I got bent out of shape with all this too a while back, I mean they can send a man to the moon, but why do they bother with making digitals that display tenths of a degree when you never know if it is even within a couple..LOL!...geesh!

As long as they are all within a couple degree target zone of each other, it will have to be good enough for me I guess.

~Doug
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"a snake in the grass is a GOOD thing"

Check out our site, and our Temp Gun FAQ, for more details on Temp Gun use, emissivity, and reptile applications.

Temp Guns measure reflected surface temp. Air has no reflection, so they don't do air temps. But Temp Guns, at least Pro Exotics Temp Guns : ) will be accurate to a tenth of a degree.

I suggest using a digital min/max thermo for air temps, and especially for checking overnight lows, and Temp Guns for surface temps, like basking spots and hot spots.
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robyn@proexotics.com

ShipYourReptiles.com
Pro Exotics Reptiles

Thanks Robyn,
Hah, just looked up the specs for the Cen-Tech gun that I have and it states an accuracy of - 4 degrees F below 212F...like WTF, what a useless piece of junk. Dang, should've gone ProExotics!

Robyn,.......

Now I'm not saying they aren't very accurate, and I have a PE-2 as well. But if they are accurate within a 10th of a degree, why would the label on them state they are accurate within Plus or minus 1.8 degrees?. Depending on which side it is, this could be a fairly substantial difference.

I have aimed it directly at other thermometers of different types, and have come up with pretty similar temps, so they seem to be doing the job just fine for me. But you can shoot it at the same thing several times and come up with a variation of more than one 10th of a degree quite often.

Certainly not making a big deal out of it though, just stating some facts is all..LOL!

best regards, ~Doug
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"a snake in the grass is a GOOD thing"

Plus or minus 2 is the official spec, but in my actual use and experience, I find accuracy, and repeatability, to be within a tenth of a degree : )
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robyn@proexotics.com

ShipYourReptiles.com
Pro Exotics Reptiles

I can buy the "repeatability" thing very easily, but to KNOW without question they are accurate within a 10th of a degree, you would need another "control" thermometer gun that was ABSOLUTELY, INDENIABLY 100% accurate, i.e.....and I DO mean 100% accurate, not 99.9% or less.

Something that insanely accurate certainly isn't going to be selling for $25 or $50 dollars..LOL!, this is a fact. More like something NASA would use that cost many many thousands to conclude what you are saying with the very minute difference of one 10th of a degree.

But in any case, I think they(the PE series) do a fine enough job for what any snake breeder/hobbyist would need them for.

best regards, ~Doug
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"a snake in the grass is a GOOD thing"