# IR camera results analysis

1. Jun 8, 2012

### fictionx

Hello all,

I'm currently using an infrared camera to determine the emissivity of a steel. The camera "sees" whatever radiation entering the objective, and calculates the temperature of the steel by assuming it's emissivity is 1. I figured I could use an energy balance to find the emissivity:

σ(Tc)^4 = εσ(Ta)^4

where Tc is the temperature that the camera says and Ta is the actual temperature. Because the camera assumes blackbody behavior, I do not include the ε on the left hand side.

My question is, do I need to somehow incorporate the temperature of the surroundings in my equation? I wasn't sure if I am supposed to add it to the right hand side and use an emissivity of 1. It changes the outcome drastically.

Thanks,
fictionx

2. Jun 8, 2012

### tygerdawg

We regularly use a FLIR camera for testing at my company. The emissivity value for the test product was determined experimentally. Multiple thermocouples were placed on the actual part and the emissivity value of the IR camera was "calibrated" until acceptable results were obtained that correlated to the thermocouple values.

We also discovered that the IR camera was very sensitive to
• incident angle of camera-to-part
• distance of camera-to-part
• ambient temperature
• ambient air currents
• elevation of camera-to-part
• probably some other things I can't remember

Our testing procedure now incorporates setups to control all of those various sensitivities.

3. Jun 9, 2012

### fictionx

That's pretty intense thank you for this information. Eventually I'm going to be trying to use our camera to determine the temperature of a moving granulate salt in a screw heat exchanger which has IR optical glass on top. Another problem I'm running into is that when the glass gets warmer it also emits and it screws up the results.