Originally Posted by Pres2play
John, have you tried the Klein off-screen to rule out heat? I know OLEDs don't put out heat like plasma, but worth a try.
The OLEDs produce more heat to the area where behind are located the electronic circuits, which is usually its not to the center of the panel where we are measuring.
You can use an Infrared Digital Temperature Thermometer with laser aiming to find out where the electronics are located.
When you are using the Klein K-10A with the extension tube (with or without the hood), and you leave some millimeters distance from the screen; for the instrument to not touch/force pressure to the panel; this is a non-contact measurement also, since you have the distance from the extension tube + the distance from the Klein's light mixing chamber (which has a smaller internal extension tube also). Klein designed to not be affected from thermal issues even if you are using the meter for days in contact mode.
Here is an photo Klein K-10 optics/electronics:
is the same photo with higher resolution.
When you take non-contact measurements, there NIST specifications about what extension tube you have to use.
Here is an example of a professional extension tube SpectraCAL is using for Minolta or JETI; or other spectro with very narrow FOV.
At the left side is the CEO of Klein Instruments (Luhr Jensen), at the right side is the Lab Director of SpectraCAL (Darryl Bird).
Here is a a Minolta CR-200 (Chroma meter) with extension tube: