TE-Q1 temperature readings not stable

[maarten]

Hello All,
(I am new to thermal imaging, so could be easily that I am doing something wrong here  )

I bought a Thermal Expert TE-Q1. I have been trying to get reasonable accurate (or better said: reproducible)  readings. In another topic it is described that the system needs a couple of minutes before it stabilizes, which I noticed as well. The only problem is that even after 5 to 10 minutes, if I walk around with it and get back to the same spot minutes later, readings can be quite different.

Any idea what it is I am doing wrong here?
I have the Android version and use it with a Samsung phone (S7)

[railrun]

What do you mean with different? 0.1 °C, 1 °C or 10 °C?
What (material) and how do you measure it? Same distance and angle?

[maarten]

This morning I did some tests. A chair (fabric) in the living room.
Attached the camera and started the app and configured a point temperature. All measurements are done from the same standing point and measured at the same spot of the chair
[time] [temperature]
00:25 15.7
01:30 16.6
04:30 17.4
06:00 17.8
07:50 17.8
Then I walked into another room (a few degrees colder), measured some colder windows there and moved back to the chair.
10:00 17.2
then I cancelled the point temperature measurement and reinstated it (without exiting the app or detaching the camera)
11:00 18.5

I've seen similar issues with major temperature differences when I put the phone with camera on a table or so. When I pick it up a few minutes later the temperature of the same surface can easily be 2 degrees different.

In the end I would like to measure windows and other building structures. I know glass has quite a different behavior but my issue is already with easy surfaces.

[railrun]

Tested it with my FLIR E60. Measured a wood-panel, 21.3+/-0.2 °C.
Then i put camera for 5 minutes outside (7 °C). Get it back inside an measured 21.0 °C. After 5 minutes it showed 21.3 °C
But that‘s what I expected. To calibrate a thermal camera you will have to turn it on for 30 minutes, to get a stable reading. I believe Fraser can explain it much better.

[Vipitis]

There is burn in and no FCC on the thermal expert.

Maybe the chair warmed up during your resting

[maarten]

Thanks for the input. You all help me troubleshoot the case

What do you mean with "burn in" and FCC?
I've seen stats in this forum with changing temperature readings over time (graphs). Is that what you are referring to with burn in?
I would have hoped the behavior would be that the temperature initially changes fast but slows down after some minutes (and maybe stabilizes completely at some point, although by that point the battery of the phone probably ran out already). Here it doesn't seem to be the case, see for example the switch off switch on of the point measurement. after that action the temperature reading jumped more than 1 degree.

I am trying to understand whether it is a software (app) issue or the camera itself. The sudden jump after switching off switching on seems to suggest software, but who knows.

Note that times I logged are minutes:seconds. I don't think the chair changed much in temperature within the total measurement time of 11 mins.

[Berni]

The TE-Q1 is sensitive to the internal ambient temperature around the sensor as all such microbolometer sensors are. When the case temperature of the camera changes too much it needs to be calibrated again with the usual procedure of putting the lens cap on and clicking calibrate.

This is the main reason why it drifts a lot as its warming up because the case temperature is constantly changing. Once its warmed up and you expose it to cold or hot air, this changes the case temperature again and makes it drift again.

[maarten]

So it could even be that the phone heating up (battery use) or my manual focusing would influence the temperatures?
I've just been experimenting and it looks like the calibration is a major factor indeed. Thanks for the tip.

Maybe I need to see if I can hook up the camera to a laptop or so. I've been looking a bit what kind of cable I would need for that. Still trying to figure out.

[Berni]

Yes touching the camera with your warm hand can change the temperature of the case too. This is why a lot of bigger cameras have an automatic shutter inside to be able to perform this calibration on its own whenever it noticed the internal temperature inside the camera changed too much.

For cables they are a bit tricky to find in this configuration of a micro USB socket to USB A plug. I just made my own by cutting the end of a USB cable and soldering a micro USB on the end.