NW-Bound
Give me a museum and I'll fill it. (Picasso) Give me a forum ...
- Joined
- Jul 3, 2008
- Messages
- 35,712
I agree with what's stated above, but without an emissivity correction on the IR gun, a quality thermocouple will still be more accurate for the purposes discussed in this thread. At the very least, an operator of an IR gun should be aware of it's limitations and how it works. I'll gladly wait 5 to 10 seconds for an accurate reading from a thermocouple over an instantaneous, potentially inaccurate reading from an IR gun that hasn't had emissivity dialed in. Looking at the IR gun shown in the picture, it appears that one doesn't have the means to adjust for emissivity.
Most IR thermometers are set for emissivity of 0.95-0.97. This covers much of the surfaces that the user encounters in real life.
The reading would be way off for shiny metallic surfaces which have much lower emissivity. Even if the user can adjust the emissivity, I wonder how he knows what value he should set it to.
And IR guns have another limitation. The way an IR works, it measures the temperature difference between the object in sight and itself. It has a cold-junction temperature compensation, just like a thermocouple does.
I have found that if I take my IR gun outdoors to take measurements, as heat is soaking into its body, the readings start to get off. This could be because of the thermal gradient within the gun itself.
If I let the temperature of the IR gun equalize with the outdoor ambient perhaps the reading will be good again, but I have not tried this.
Still, the IR gun is what AC servicemen use. And it is getting accurate enough to be used in routine medical applications.