Some esoteric materials can give off readings, but clear glass, clear water (and dirty water), a piece of wood, substrate, plastic, a brick wall, they all read very accurately with an infrared temp gun.
Esoteric materials include things like gold, liquid mercury, carbon fiber, surfaces you are not likely to encounter in the reptile world. Polished aluminum, that DOES have it's own emissivity setting.
There was a similar thread here at BP.net recently, I did a long reply for it, which instead of just linking here, I will copy, there is lots of info there : )
from Herpstat vs. Tempgun thread-
BP.net thread
The difference you are seeing has more to do with the tool than the actual temperature.
A thermometer probe is designed to measure air temperature. A temp gun specifically measures surface temps. A temp gun doesn't measure air temps at all. It measures reflected surface temps, physical objects/surfaces.
Using a probe like that to measure surface temps is very difficult to do. You have to tape it down, bury it, all kinds of different tricks to get surface contact for a reasonably accurate measurement.
If the probe is water proof, you can submerge it and it will measure those temps just fine, because it is completely surrounded by the "surface". That doesn't help with heat tape setup, but it may help to understand the concept.
In a basking lizard setup, using a probe from either a thermostat or a digital thermometer- trying to take the surface temp of the basking spot is incredibly difficult, again because of the lack of contact for the probe. Using a temp gun, I can read the actual surface temp at 134F (or whatever it is). Using the probe, I may be able to only get it to read 127F. If you raise the probe off the surface, so it is measuring only the air temp, even 1/8" off the surface, the reading may go down 15-20 degrees. Air doesn't hold a temperature anywhere nearly as well as a physical object with thermal mass. That is why on an 80F degree day the asphalt might be 135F.
Surface and air temps are radically different. Use a probe to measure air temps, and a temp gun to measure surface temps. (there are specialty probes/tools that measure surface temps, but they don't come on thermos that we use for reptiles).
In the end, it is all ok, because it is all relevant.
Your temp target is the temperature that your reptile has access to. You want a 92F hotspot (or whatever). The setting on your thermostat is not so important, as long as the RESULT in the cage is 92F. Depending on probe placement, your thermo setting might be 92F, 85F, or 103F.
Your snake doesn't read the number on the thermo, it just searches for accessible and usable temps, so the setting doesn't matter. The result does.
A temp gun is incredibly accurate. If you are measuring surface temps, and for this application (heat tape to create a hot spot) you are, it is the most accurate tool you can have. Make sure the lens is clean and free of dust (use a q-tip to clean), you have a charged battery, and if the unit has adjustable Emissivity, it is set to 95E.
Also be sure you are measuring from an appropriate distance. A unit like the TG1/PE-1 has a 1:1 distance to spot ratio. At 1 inch you are measuring a 1 inch spot. At 6 inches you are measuring a 6 inch spot. You wouldn't want to take a reference measurement of 3 inch wide heat tape from 6 inches away, you would be measuring the heat tape PLUS the rest of the cage surface.
I typically use the TG1 unit at 2-3 inches away for hot spots, basking spots, etc.
Finally, if you want a reference, use the ice water bath test. Assuming a submersible thermo probe-
Get a Super Big Gulp sized cup. Fill it with crushed ice (crushed ice will give more accurate result compared to cubes). Fill with cold water. Use a spoon to slowly stir the water. Slowly. The liquid water will get right down to the freezing point at 32F. If you stir quickly, you create heat, stir slowly.
Submerge your probe in the water. Continue to stir, see how close you can get to 32F. Should be able to get within a degree. Salt content, altitude, there are a couple of factors that will change the absolute temp result, but you will get close.
Now take the surface temp of the water as you stir, from an inch away, with your temp gun. This method using the temp gun is INCREDIBLY accurate (clean lens, good battery, 95E).
If your thermostat is accurate, and it should be, you shouldn't see more than a tenth of a single degree difference between the two.
That is a simple test, and yields a terrific result. A boiling water test is NOT the same. Water boils at different temps (salt content, altitude) but more importantly a temp gun would be measuring the tiny droplets of water in the steam and not the bulk water itself. Just FYI.
In our setups at Pro Exotics, the setting on the thermo is RELEVANT to the cage hot spot temp. We check actual temp with the temp gun, and adjust the thermo up or down accordingly. Probe placement, heat tape, heat pad, substrate, air flow, they all affect the resulting hot spot, but these things are all related, and once you understand the nature of that relationship, it all becomes pretty straightforward and easy : )
Originally Posted by Robyn@SYR
Some esoteric materials can give off readings, but clear glass, clear water (and dirty water), a piece of wood, substrate, plastic, a brick wall, they all read very accurately with an infrared temp gun.
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