Using Temp Gun Correctly

[BlueBella]

I have been using my temp gun to measure the basking spot about 2 inches off the ground perpendicular to the slate. I understand emissivity but I don't really understand the distance to spot ratio. My gun has a ratio of 12:1 so 12 inches measures a circle with a 1 inch diameter. Does this mean I have to be 12 inches away to get an accurate reading? I haven't measured it from that far away because I thought the closer the better and my tank isn't even tall enough to get that measurement without tilting the gun. I use a thermometer with probe sometimes to double check and it usually reads the same as the temp gun when it is held 1-5 inches away. So have I been measuring it wrong all this time? I'm not super worried about the temps in general as I have the thermometer with probe, and Deckard is acting fine, but I just need to know if I'm using the temp gun right.

[Rocksor]

You don't have to be 12" away. The closer you are the more accurate the reading.

[mb606587]

Yes, the closer you are the better but you should still be able to get accurate readings from 12", probably even 24". That distance to ratio formula is designed for how far away you can get and still get an accurate measurement, more for people who are trying to use the gun from a distance or for people that are trying to measure a tiny area. Basically for every inch in size the target you're measuring is, you can reliably measure from 12 inches back with a 12.1 ratio like you have. So if you are trying to measure the surface temperature of a 6 inch rock, you could get an accurate reading from as far as 72" away, assuming the beam is unobstructed.

[kingofnobbys]

Like already pointed out the ratio of 12:1 simply means the spot that's measured is 1" in diameter at 12" from the surface. The closer the smaller the spot measured and less chance of including cooler back ground surfaces in the measuring spot which will result in an erroneous temperature measurement.

If your thermometer has the ability to dial up an emissivity , you can set this to conform to the emissivity of the surface who's temperature you are measuring and this will ensure best accuracy in the temperatures being measured.
There are tables of emissivity online.

Other thing to be careful of is accidentially measuring the temperature of the reflection of the basking globe, this will result in high temperature reading.

If you want more information , PM me and I'll give you some links that are more detailed.

[BlueBella]

Yes, the closer you are the better

That's a relief, I'm glad I haven't been using it wrong this whole time. Thanks for the replies and advice!