Emissivity of textured bed
Does anybody have a definitive value of the emissivity? I am using an IR camera to check bed temperature, and using a value
of 0.76 the temperatures reported by the camera and the built in sensor seem to be close. The temperature distribution seems
pretty good but it would be nice to have more confidence on the actual temperatures.
Oxidized steel is going to have an emissivity around 0.8. Given the shinier surface of the powder coating, 0.76 doesn't seem out of bounds. I doubt you are going to get a definite answer though. Best you could do is to determine it experimentally, if you have access to a good thermocouple.
calibration
use a calibrated contact thermometer or temp. measuring device to confirm the actual temp of the surface, then adjust emissivity of the camera until it matches the temp. of the measuring device. This may be a good place to start.
You should be most interested in the relative temp, if it always reads 245° when adhesion is great you just have to confirm that with the settings you have selected it reads 245°.