Infrared thermometer guide needed

[legrandice]

So i have a rosewill infrared that i got from amazon a few years ago. It seems to be pretty accurate.

Today i went out to put some mail in the box and though it was pretty cold out so i had better take another trip our with the thermometer.

Outside temp is currently 5 degrees according to in town weather station and 10 degrees according to thermometer that is in a window next to the house.

My infrared was reading really cold temps? Why?

Here are my readings:
Mailbox


Aluminium sided enclosed trailer



Window sill where wireless temp thing is located

 

[MasterMech]

Most likely it's out of calibration. Does it have a way to adjust it? Sometimes it's referred to as an Emissivity adjustment.

 

[Badger]

My best guess is that it has to do with the emissivity of the objects that you are measuring. Different materials with different surface finishes radiate energy(heat) different. Black typically radiates the most energy at a given temp so I am surprised that it reads the lowest.

Also, I must admit it has been a long time since I studied radiative heat transfer... Maybe someone else remembers better than I.

Either way, we use infrared guns at my work frequently for quick measurements. Typically they are close to the thermocouple measurements, but never exact. For what ever reason I get the worst readings off of magnet wire on motors.

I'd just go with that you are with in 5 degrees f of each measurement which is close enough. It doesn't matter if your stove temp is 500 or 505.

 

[legrandice]

Most likely it's out of calibration. Does it have a way to adjust it? Sometimes it's referred to as an Emissivity adjustment.

It is a cheap one...no adjustment.

My best guess is that it has to do with the emissivity of the objects that you are measuring. Different materials with different surface finishes radiate energy(heat) different. Black typically radiates the most energy at a given temp so I am surprised that it reads the lowest.

Also, I must admit it has been a long time since I studied radiative heat transfer... Maybe someone else remembers better than I.

Either way, we use infrared guns at my work frequently for quick measurements. Typically they are close to the thermocouple measurements, but never exact. For what ever reason I get the worst readings off of magnet wire on motors.

I'd just go with that you are with in 5 degrees f of each measurement which is close enough. It doesn't matter if your stove temp is 500 or 505.

This one measures fairly accurately until the temps are below 0F....I only use it for entertainment anyways. Thanks for the good info.