Operating temperatures Flir, Hti, Uni-T - Page 1
Forum section: electronics / general

author: Architector
author_rank: Newbie
timestamp: January 11, 2023, 08:32:19 am
content: Hello,I‘ve compared datasheets of several thermal cams. As I can see, chinese manufactures write operating temperatures from 0°C to arround 60°C. Flir offers (for E4 f. e.) -15°C to ≈ 60°C.What do you think is the reason for the difference? Display? Batteries?Did anybody use Uni-T or Hti devices in colder environs, than 0°C?

author: Bill W
author_rank: Super Contributor
timestamp: January 11, 2023, 12:56:28 pm
content: Two possible answers.Yes simplistically it may be to (claim to) keep batteries in their 'operating range', but that is simply a paperwork claim. FLIR etc are not using 'magic cold weather batteries', it may help keep compliance people happy.More fundamentally they simply cannot be bothered to make the sensor work from 0°C down to -15°C and retain desired temperatuee accuracyThat bit is somewhat tricky and may cause costs at manfacture depending on how it is done.Even then, look at a FLIR fire camera instructions. For the camera you can take into a fire, 250°C for 15 minutes and yet the battery and instructions still says "do not take into fire or expose to temperatures over 60°C"Bill

author: wraper
author_rank: Unknown
timestamp: January 11, 2023, 01:05:38 pm
content: It's not like they will not work below rated temperature. It's simply not guaranteed and there was no extensive testing to ensure that. Also wide operating range guarantee often requires using components rated for wider temperature range. Usually they are the same parts with more lax testing.

author: Architector
author_rank: Newbie
timestamp: January 12, 2023, 03:12:56 pm
content: Thank you guys!So I will save money. Just orderd one UNI-T UTI320i with hardcase and two batteries for 560€ plus VAT. Think, that‘s a good value.

author: markb1980
author_rank: Regular Contributor
timestamp: January 15, 2023, 10:44:12 pm
content: I have seen Guide cameras drifting and reading 5-10°C lower then the actual temperature at -6°C. I have not tested my Infiray in that conditions.When you get your UTi320E please post a review and also some screenshots of the reporting-software. Thanks!

author: Fraser
author_rank: Super Contributor
timestamp: January 16, 2023, 07:58:49 am
content: I spoke with FLIR some years ago regarding the temperature measurement accuracy of the Ex series of cameras. I questioned the accuracy of the measurements as the cameras ambient temperature environment changed. This question stemmed from the fact that the Ex series uses a microbolometer that is not temperature stabilised. It is operated in a thermal equilibrium mode that at normal ambient temperatures of around 20 Celsius will see it reach thermal equilibrium at around 30 Celsius die temperature. FLIR advised that the Ex series camera measurements will see an increasing amount of error as the ambient temperature moves further away from the temperature at which the camera was calibrated. In the case of the E4, the datasheet clearly states that the accuracy is +/-2 Celsius or +/-2% within the ambient temperature range +10 Celsius to +35 Celsius. The reason for this range is that it surrounds a calibration environmental temperature of ~ 22.5 Celsius. The cameras measurement system takes account of ambient temperature using the cameras built in ambient temperature sensor. It uses a correction table but that can only provide adequate correction over a limited ambient temperature range (+/-12.5 Celsius). Note also that FLIR state that the measurement accuracy applies to target temperatures above 0 Celsius. As target temperatures approaches 0 Celsius, the amount of thermal energy that is emitted from them really challenges the uncooled microbolometer thermal camera. There is also the matter of frosting and icing on the targets surface at temperatures below 0 Celsius and this needs to be considered where emissivity is concerned. It is also worth noting that FLIR actually provide an honest measurement accuracy specification that includes the limitations that apply. Many other budget thermal camera manufacturers will not provide that level of detail.The FLIR Ex series thermal cameras are a good example of a budget radiometric thermal imaging camera of sound design. The design incorporates ambient temperature monitoring, ambient temperature compensation and an FFC flag that acts as a temperature reference for dynamic calibration of the measurement system. The Ex series does suffer from the effects of not having a temperature stabilised microbolometer but its accuracy is considered adequate for the intended application and a non-stabilised microbolometer saves on the power consumption front.So how does a professional thermal imaging camera maintain its measurement accuracy ? Such cameras incorporate multiple temperature sensors inside the camera to monitor chassis temperature, ambient temperature, Microbolometer Die temperature, FFC flag temperature and lens block temperature. The microbolometer is often thermo-electrically (TEC Peltier) temperature stabilised to keep the die at a temperature of around 32 Celsius no matter what the ambient temperature may be. The measurement system uses the information from the various temperature sensors and the FFC flag events to maintain the measurement accuracy of the camera over a wide range of operating conditions and temperatures. With a professional radiometric thermal imaging camera there is the slack in the BoM budget and profit margin to permit comprehensive temperature compensation and multi-point measurement calibration at time of production. This is what you are paying for when buying professional radiometric thermal imaging systems. Budget systems just do not have the profit margins to support such accuracy enhancements. A classic case of getting what you pay for.An added advantage of providing the microbolometer with temperature stabilisation is the ability of the OEM to fine tune a cameras performance via its microbolometer gains and biases to provide the best possible imaging performance because the microbolometer die temperature is known and well defined. Such fine tuning is limited if the microbolometer die temperature varies with ambient temperature.Some modern budget thermal camera do not include an FFC flag in their design. Whilst this simplifies the mechanical design, lowers BoM cost and avoids the frozen image associated with an FFC event, it also deprives the cameras measurement system of the "known temperature" calibration reference that the FFC flag offers during an FFC event. An uncooled microbolometer thermal camera that does not have a FFC flag is compromised when it comes to temperature measurement accuracy. Such a camera can still produce "pretty pictures" thoughFraser

author: markb1980
author_rank: Regular Contributor
timestamp: January 16, 2023, 09:05:47 am
content: I understand you Fraser but the TO told in another thread that he is an construction-engineer and he want to do building-inspections professionally. So I would think some kind of accuracy is key in that regard. "Pretty colorfull images" look nice but you should be able to see also if you are dangerously close to the dew point or still 3°C away. See:https://www.eevblog.com/forum/thermal-imaging/uni-t-uti320e/

author: Fraser
author_rank: Super Contributor
timestamp: January 16, 2023, 09:30:37 am
content: Then he would be wise to buy a thermal camera that provides comprehensive specifications regarding measurement accuracy and under what conditions those specifications apply. A camera datasheet specifying the common "+/-2 Celsius and +/-2%" for accuracy is incomplete in its detail. Professional thermography can be a very expensive business where the purchase of a camera is concerned. The OP needs to consider the level of accuracy he is required to provide and under what conditions and that will help determine which cameras are best suited to the role. One problem we see with some manufacturers is a "copy and paste" attitude to thermal camera specifications. They look at other manufacturers like FLIR and just copy the specifications in order to appear the same in terms of performance. I have tested cameras that took ages to reach thermal equilibrium for accurate measurements, were basically inaccurate at all measurements points due to poor calibration, had poor Radiance to Temperature conversion tracking over the measurement range or were just plain junk with inaccurate measurements provided. Decent calibration of the camera at time of manufacture is essential if the cameras is to be a decent performer for temperature measurement. Sadly such enhanced calibration is expensive. It should also be noted that FLIR cameras are all calibrated at the factory to a decent standard but the professional models are calibrated with a greater number of reference points per range. When a company offers a FLIR camera with a "calibration certificate" it is usually just a calibration check using a known accurate test source and not a different calibration to that provided to other cameras coming out of the factory.Fraser

author: Fraser
author_rank: Super Contributor
timestamp: January 16, 2023, 09:39:28 am
content: I just checked the specifications of the Uni-T UTi320E.https://uni-trend.en.made-in-china.com/product/UFAtNDSZrPWV/China-UNI-T-UTi320E-Professional-320-times-240-Infrared-Thermal-Camera-with-3-5-prime-prime-IPS-Screen.htmlThat is very much a budget camera and I see the usual generic +/-2 Celsius and +/-2% for the accuracy specification but no detail of where that specification is applicable. That is the first question I would want answered by UNI-T if I were buying that camera. I also note that they claim a measurement range of -40 Celsius to +400 Celsius. That -40 Celsius figure had me rolling on the floor laughingSadly the marketing departments of some companies get a bit carried away in an effort to "out-specify" the competition. The UTi320E will likely deliver the performance the OP desires but this is very much a budget camera at a budget price. You have to start somewhere thoughFraser

author: IR_Geek
author_rank: Regular Contributor
timestamp: January 16, 2023, 01:06:19 pm
content: Quote from: Fraser on January 16, 2023, 09:30:37 amAs usual, Fraser is nailing! Couldn't agree more with the above and would go one further with a need to at least periodically check with a known good blackbody. If performing scientific measurements, then checking the calibration (or re-calibrating) on each power up may be required.

author: Architector
author_rank: Newbie
timestamp: January 24, 2023, 08:01:13 am
content: Hello,thank you for the detailed information. I canceld my purchase, as I do have time. I will start wirh thermal imaging next winter. Is there a camera, you can suggest for thermal imaging homes from outside in winter (we usually do have some temperatures betewwn 0°C to -5°C here. What I’ve liked the UTi320e was the big big FOV with 56°x42° in order to get a wide ankle and as much house on an image, as possible. For me it is not so very important to get 100% correct temperatures. Much more important are the differences of temperatures to detect thermal bridges in constructions. To find weak points. For calculating a energy-balance of a house, I need to do accurate modelling all walls, windows with their coefficients of thermal condictivity into a mathematical model in therms of the german building-energy-law. That‘s much more than a thermal image made with the best equipment can say.While doing blower-door-tests, I want also see, where the leaks are. For me it is not so very important, how high /low the temperature really is. I just need to see the problems by visualizing the deltas. For the temperatures themselves, I know about them. For me, mainly the differences are sufficient enough.As you can see, a budget camera might be the right thing. What do you think? Do you know other UTi320e alternatives, with large FOV in a pricerange up to max 2.000€?

author: Fraser
author_rank: Super Contributor
timestamp: January 24, 2023, 09:33:35 am
content: I strongly suggest some reading regarding Instantaneous Field of View (IFOV) and its effect on the thermal detail that may be captured in an image at a specified distance. it is sometimes discussed as "pixel size on target" meaning the minimum area on a target that is seen by a single pixel and so the finest detail that may be seen. Bear in mind that for "detection" a target area is normally expected to fill 4 pixels (2x2). The term "Pixels on target" become a specification of interest for those wishing to detect small areas of temperature difference in the observed scene. Most often of interest to those wishing to see a small thermal target at a distance, or a larger target and a very long distance !You often have a relatively low resolution thermal sensor array and you have to use the pixels wisely if you want image details to be available for later analysis. I show the effect of IFOV in my review of the Infiray P2 Pro camera.https://www.eevblog.com/forum/thermal-imaging/review-infiray-p2-pro-thermal-camera-dongle-for-android-mobile-phones/msg4575070/#msg4575070Whilst a wide angle lens may provide a nice complete image of a building, you lose the detail due to the large IFOV. It is sometimes better to use a thermal camera that offers a smaller HFOV, of say 24 Degrees, lock the range and span and then create a detailed image of a building using multiple pictures. Panoramas are possible with this technique as well. Thankfully a 24 degree HFOV lens does not normally suffer too much with barrel distortion so image stitching is possibleYou have to remember that in a 320 x 240 pixel thermal array you only have 320 pixels in the horizontal plane that are viewing the whole horizontal scene presented to it via the lens system. For building thermography the minimum recommended camera resolution is 320 x 240 pixels with a small FOV lens. For greater FOV there may be a need for 640 x 480 pixel sensor arrays. A perfect camera for such work would offer a 640 x 480 pixel sensor array with a choice of 24 Degree HFOV and 45 Degree HFOV lenses. Some cameras offer a 24 Degree HFOV with the option of a X0.5 supplementary lens for when a wider field of view of closer viewing position is needed, The FLIR Ex0 series of cameras were examples of such. The new Ex5 and Ex6 ranges offer interchangeable lenses rather than using supplementary lenses.Sadly building thermography for in depth analysis requires a pretty serious thermal camera and thermal analysis software. The description of what you are looking to do pushes you towards the FLIR prosumer range of cameras (Ex0,Ex5 or Ex6) cameras and they are very expensive when purchased new. The image analysis software is very good but the professional versions are also expensive. You are facing a challenge if buying at the budget end of the thermal camera marketplace. Thermal imaging and measurement for Professional use, often means professional (expensive) equipment is required.Finally, it is worth checking how many pixels are actually needed for an accurate measurement using a particular thermal camera. It would be rare and risky to rely upon the temperature (actually radiance) output value of a single pixel. Many measurements usually take account of adjacent pixel values and average the result. This avoids errors introduced by a "flickering pixel" or a pixel with drift issues. Consider this when thinking about the lens FOV, resultant IFOV and "pixel size on target". Remember, it is not pretty pictures with interpolation that is important here, it is true radiometric pixel data and its reliability in the real world. And do not get me started on predicting true emissivity of surfaces found on buildings ! It can be a challenge.Fraser

author: markb1980
author_rank: Regular Contributor
timestamp: January 24, 2023, 04:46:24 pm
content: Quote... if you can live with 256x192 resolution - I have used my Pocket2 in cold weather and I didn't expirience a temp. drift as in my Guide TIC for example. You could get a M30 for a little over budget if you wait for the right moment or you go with lower resolution and get thermography going for 600-650 EUR.I case you have facebook this person does a not of building inspections with a B1L and a Pocket2:https://www.facebook.com/Thermovision026As nativ german speaker you will maybe find that helpful to understand FOV and IFOV:https://books.google.cz/books?id=taJ1EAAAQBAJ&pg=PA83&dq=mark+b+thermografie+geometrische&hl=de&sa=X&ved=2ahUKEwiFxpTz1OD8AhXY6CoKHVL1C-EQ6AF6BAgLEAI#v=onepage&q=mark%20b%20thermografie%20geometrische&f=falseProblem with quite low resolution is that you can't see much details in overview images. So you have to step in and get detail-shots of each area of interest (if possible). So I disagree with fraser in that point! It is doable in most cases (not with a huge factory or 12 floor hotel but with a private home for sure)! I agree - a 8000 EUR camera with 640x480 resoution would make things easier and faster but you have to do quite some work to earn that money.So it comes down to your budget. You can start with a little less then 320x240 for way under 1000 EUR or you go a bit more then your 2000 EUR budget to get a M30 with a 384x288 resolution and a little narrower FOV then the B- and Pocket-series.