FLIR E4 Temperature Readings Incorrect - Page 1
Forum section: electronics / general

author: xbnipx
author_rank: Newbie
timestamp: November 06, 2016, 04:34:55 pm
content: Hi GuysDo you know whats up with this E4. There is an Asterisk near the temperature symbol and the temperature is way off.

author: SeanB
author_rank: Super Contributor
timestamp: November 06, 2016, 04:40:04 pm
content: Not warmed up yet, and you are looking at a shiny reflective surface, so are picking up the temperature of whatever is reflecting off that pan. Likely you are in a kitchen and it is really cold outside, and you are facing a window.

author: xbnipx
author_rank: Newbie
timestamp: November 06, 2016, 04:46:17 pm
content: I don't think its the case of being warmed up. I took this apart to clean the lens and I must have done something. Even pointing at hotter objects I get 0F - single digits. So the relative change in temperature is fine its just the temperature is off.Could I have messed up the calibration

author: Fraser
author_rank: Super Contributor
timestamp: November 06, 2016, 05:29:32 pm
content: The E4 has a chassis ambient temperature sensor. If that has failed or been damaged/disconnected, it will cause wild inaccuracies in the camera calibration as this sensor sets the FFC flag temperature variable in an FFC event.The image is otherwise OK so this is a table offset fault and not corruption of firmware or calibration tables.Please detail how you cleaned the camera..... did you take the casing off of the chassis or disassemble the chassis ?Fraser

author: xbnipx
author_rank: Newbie
timestamp: November 06, 2016, 05:45:51 pm
content: Yea I disassembled everything. There were times where I hooked up the camera without the chassis. I was trying to remove a dark spot on the sensor. (I couldn't remove it might be a dead pixel.)Im guessing the ambient temperature sensor is the 6 pin chip on the side of the board?

author: Fraser
author_rank: Super Contributor
timestamp: November 06, 2016, 05:59:37 pm
content: The sensor is a 6 pin SMD marked T730 and sits on its own semi-isolated area of the PCB. It looks like a little PCB island that is connected to the PCB at one side only. It's quite fragile !Warming and cooling the T730 makes the E4 apply the appropriate offset table. The E4 is NOT temperature stabilised so have several offset tables to suit differing ambient temperatures. Selection of the wrong offset table would create incorrect readings, especially after an FFC event.Fraser

author: xbnipx
author_rank: Newbie
timestamp: November 06, 2016, 06:39:38 pm
content: Ok I took apart the camera again. I placed my finger onto the thermal sensor and the temperature barely changes maybe 1-2 F. Isn't touching it suppose to cause a drastic change in temp, Since its the reference temperature?

author: Fraser
author_rank: Super Contributor
timestamp: November 06, 2016, 07:14:46 pm
content: It should make a difference. Try warming it with a hair dryer or with a tea spoon that has been heated in hot water, just press the hot spoon on the SMD casing. Do the same with another spoon that has been in the freezer. That should make a major change occur. If no change occurs, look for cracked SMD solder joints on the temperature sensor or damage to the PCB tracks.

author: Fraser
author_rank: Super Contributor
timestamp: November 06, 2016, 07:18:27 pm
content: The sensor is an LM73 and the data sheet may be found here.....http://www.ti.com/lit/ds/symlink/lm73.pdf

author: xbnipx
author_rank: Newbie
timestamp: November 07, 2016, 02:56:34 am
content: ok I used the continuity mode on my fluke and found that there may be a short in the T73 chip. The short is between 4 and 5 or 1 and 2.1 and 2: Address and Ground4 and 5: SMBCLK and ALERTIm guessing either is bad. I don't see any physical short which brings me to believe the chip is fried internally and creating a short. Hopefully this is the problem because it would be a $1.99 fix

author: Fraser
author_rank: Super Contributor
timestamp: November 07, 2016, 12:09:32 pm
content: Unusual but not impossible. Maybe something touched during your tests and killed it ? just bad luck if that is the case. I regret I am not familiar with the LM73 but at least it is not very expensive and relatively easy to replace. If you are not a frequent SMT reworker and do not have suitable Hot air rework tools, I recommend using a sharp craft knife to cut the legs away from the chip body and desolder the pins individually. It Is safer for the PCB that way and easier for you. Fitting the new sensor should be relatively easy if you tin the pads and apply flux to both pads and pins before soldering into place, one pin at a time with a small soldering iron tip. Be careful to not overheat the sensor in the process. Some temperature sensors do not like being cooked !Fraser

author: xbnipx
author_rank: Newbie
timestamp: November 07, 2016, 04:19:20 pm
content: I have a hot air rework station so knife won't be necessary. I will be careful when I remove it. Also a digital microscope is coming in the mail so ill look for any other possible physical damageIf I replace the chip and it still doesn't work idk what else it could be. I could try reloading the factory 2.3.0 firmware

author: xbnipx
author_rank: Newbie
timestamp: January 02, 2017, 08:38:53 pm
content: Replaced the chip. No dice the temperature readings are still off. Hmm, Do you think this could be software related? Could a recalibration bring it back to spec?

author: Fraser
author_rank: Super Contributor
timestamp: January 02, 2017, 11:25:56 pm
content: Sorry to hear this news.Remember that you dismantled the camera and it was not a firmware update or modification. As such it is very unlikely to be a calibration table issue.The camera also functions to the point of displaying a good image. Not what you would expect to see from corrupted calibration tables or routines.The best bet is still a problem in the cameras ambient temperature sensing. there is also another possibility though ..... it is not a nice one though.The microbolometer in the E4 is not temperature stabilised but it uses its own ROIC self heating to raise the array to around 30C. The sensor contains two semiconductor junction temperature sensors that feed die temperature measurements to the operating system to inform it of when the normal operating temperature has been reached. The die temperature is used in the calibration of any radiometric temperature measurements made by the operating system. If something has gone wrong with the sensor die temperature circuit all manner of weirdness in measurements may occur. Why do I consider this a possibility ? ...... The 'warm up' asterisk is present. Normally the camera starts and displays this asterisk until the temperature sensor on the microbolometer die reads the normal operating temperature. It appears that your camera stays in the 'warm-up' warning phase as it does nor 'see' the correct 30C temperature on the die.I hope I am wrong about the microbolometer temperature sensing circuit as that would be very bad news indeed. A failed microbolometer temperature sensor requires a new microbolometer. The good news is that the microbolometer comes with a 10 year warrantyReverse the E4 upgrade and return for warranty repair.I forget whether your camera model has the ability to display its service menu and whether that lists the temperature of the 3(?) temperature sensors within the camera. I have a fading memory of the service menu on the E4 providing that information. Certainly worth looking in to. It has been a long time since i worked on the E4. IIRC you had to access the service menu via the web server application within the camera. Full details of that are in the E4 teardown thread. Search for E4 service menu in that thread using Google.Once in the service menu, you will be able to see which temperature reading looks wrong. If all are wrong, the unit has totally lost its reference against which it makes internal temperature measurements.Fraser