Ir temp gun question

[Louis Charles Bruckner]

Sorry Daniel but water surface is reflective even muddy water is reflective and you will only read the temp of what eve is around it.
Even a semigloss paint job is reflective enough to fool IR guns.

just a few months back I noticed a grocery store worker using a IR gun to read the temp of food warmer that was lined with aluminum foil.
And she was on the radio calling the store manager that the warmer was broken that it was reading just 68F and it should be reading 120F

I waited for the manager to arrive before offering help.
I explained that she was actually measuring the temp of the ceiling in the store.
Both her and the manager didn't understand.
So I asked her to point it at the celling and see what was the temp was. 68F she said.

I explained what was going on and asked if the manger could get a price sticker from the delli counter.
that was blank. I knew that these stickers were a matt finish and not glossy.
and as soon as I stuck it to the pan of the food warmer the sticker went completely black.
I said ok now from that reaction I know that that surface is over 120F since the thermal paper turned black.
now lets look at that IR gun. it had a diagram on the top of it showing the sensing area size per distance from the gun.
so I showed them that reading a surface from a foot away the seining area is about the same size as the sticker and to aim the laser
at the sticker and you will get a accurate reading.

Then she said I also have to read the containers of food. I said simply just read the price sticker. as long as it is not a sticker that is glossy.
or silver.

So reading the glass of a enclosure is not a good place to get a reading. unless you put a small strip of scotch tape on the glass.
Here is a little demo I did for my technical director that didn't understand that the new parts we got to replace the old could not be thermal
imaged.
The first image of the parts lined up in glasses.
one part was put in the freezer another was put in hot water for a while and one was left in room temp for a few hours.
They all have a pice of scotch tape on them.


This image shows how the areas that don't have scotch tape are the same color or shooing the same temp.
but the areas where the tape is vastly different color shooing the actual temp of each part.


the one to the far left is the warmest of the three and the one in the middle is closer to room temp and the one on the end is the coolest.
you have to read the directions carefully of the IR gun.