The biggest difference between the cheap ones and the expensive ones is the field of view. With the cheap ones, you need to be really close up to get a good reading that doesn't average out everything in front of you. With the better ones, you can get a good reading from farther back.
I have the harbor freight model. I bought it to check exhaust temps to see if my catalytic converter was plugged. It did the job. I use it pretty regularly for non-critical stuff. You know, like checking the temperature of a sunbathing black dog:
The better IR instruments will have the ability to change the emissivity parameter within the unit that is used to calculate the temperature. If you need such capability, then you are probably aware of it but it is something to consider if you are in need of accuracy, resolution and repeatability in your application.
Right you are about emissivity. Seen some wildly inaccurate readings on shiny metal surfaces. These things have really gotten cheaper in recent years. Over 10 years ago I bought a Fluke 62 Max Plus because of the adjustable emissivity and two laser beams that were 180* apart which defined the diameter of the area being measured. Never felt confident with the one beam models when at a distance. It wasn't cheap then and would be an extravagance at today's Fluke prices (which I wouldn't repeat). Good to see prices have really come down.
Unless you know the exact emissivity of the surface and are working in laboratory conditions, it's kind of worthless to be able to adjust the instrument. Once you look at what a thermal imager "sees", it becomes clear that low emissivity materials (reflective metals come to mind), not only throw off the temperature readings by having a vastly different infrared emission spectrum, but they also reflect so much IR that you often just pick up a reflection of your own body heat rather than the surface itself.
I can identify with that. If I had to do it again I'd get a moderately priced IR gun, and if required, get an immersion probe and surface probe with thermocouple readout.
Why white paint. Wouldn't black be better.
Maybe. Getting into the weeds, with black, the emissivity varies a lot with the sheen, where gloss lowers it a whole lot, and flat black SHOULD be excellent, but that depends a lot on what the paint is composed of (dyes are not the same as pigments, and with black, that matters a lot). With white, there's a lot less variability to contend with. Pretty much any paint other than a black gloss metallic is going to get you over 0.90, and that should be good enough for at least decent temperature comparisons.
Probably the one I bought via their online sale a couple of months ago.
And the Ms. **** on occasion. Got to have some heat in there. LMAO
This is true for the old Cen tech ? Yellow / grey one. Our is old; maybe the new orange one is better.
-I've found that just about anything that takes a battery should have it removed when not in use. The battery either drains or corrodes. I've ruined a few of the old Maglite flashlights from storing the flashlight for emergencies and the corroded battery ruined it. The IR temp gun seemed to run the battery down faster than for the few times I used it to check HVAC duct temps. Maybe I don't know what I'm talking about either.
Not in stock anywhere close but they have another cheap one. $11
Here's a table of emissivity of various materials. Probably should verify with multiple sources of info if you are getting into it that much. One of the things I want to do is check the temp of concrete prior to a spray foam job and I see concrete is listed.