Questions about ThermApp - Page 1
Forum section: electronics / general

author: Hagrid
author_rank: Contributor
timestamp: August 17, 2017, 06:32:35 pm
content: Hello everyone, some of you maybe know the ThermApp thermal camera made by Opgal. This camera has a focus able lens which is really nice in my opinion. However, it also enables the user to change the lens. So while the lens is removed dust and other nasty stuff can get stuck on the sensor and accumulate over time.This makes me think if such a sensor can be cleaned somehow at all. Most LWIR optics are coated as far as i know, so i assume you could ruin your sensor really fast.Greetings, Hagrid

author: Ultrapurple
author_rank: Super Contributor
timestamp: August 18, 2017, 07:53:26 am
content: Looking inside the Therm-App you'll see the exposed front surface of the Ulis microbolometer sensor (see photo - the spot middle bottom is a reflection not contamination). So yes, unless you practice reasonable hygiene you could end up with muck on it. However, I've been changing Therm-App lenses frequently for years in conditions ranging from home to the edge of the Sahara Desert (yes, really) and I've not yet caused any problems. As long as you use a similar level of caution as you would changing lenses on a DSLR, you'll be fine. My tips areIdeally, only change lenses in a clean area free from airborne contaminants, grit, grease, small children etckeep the body of the imager facing down when you remove the lens, and place it opening-down onto a clean surfaceput the removed lens into a clean container straight awayget the next lens from its clean containerif you're feeling enthusiastic, use a bulb-type blower to make sure there's no contamination on the sensor-facing part of the lens assemblyscrew the lens into the housing and adjust focus to tasteIf you do get dust or hair contamination on the sensor, blow it away using a bulb-type puffer or a photographic-quality compressed air stream. Do NOT use your breath. There is no reason why a properly-handled Therm-App should ever get, say, fingerprints on the sensor.Most of the time I keep my 13mm f/1.0 lens attached and only change to the other lenses when there is a particular need.

author: Ultrapurple
author_rank: Super Contributor
timestamp: August 19, 2017, 03:15:26 pm
content: In case anyone's interested, I took a look at the Therm-App Pico384 sensor using another Therm-App. Almost none of the detail is visible to the naked eye because it's all sealed behind a slice of germanium.The image below is a stack of about 250, processed in Registax 6 and Paint Shop Pro. I know it's a bit fuzzy but bear in mind the source was 384 x 288! I captured the image using a 13mm f/1.0 lens screwed out to its maximum extent (max macro). The 'vignetting' at the corners is caused by the round lens aperture of the camera body (see visible image posted previously, which is rotated 90° from this thermal image).While I was working on this I discovered that fingers clutching the lens for focusing make a pretty good ersatz thermal ring flash!A better but smaller version of this image is athttps://www.flickr.com/photos/ultrapurple/35902887753/in/pool-therm-app-users

author: Hagrid
author_rank: Contributor
timestamp: August 20, 2017, 08:10:12 am
content: Hello again, thank you for the advice to keep the device clean. I noticed that your Therm-App on the picture has no grease on the thread. Mine came with quite some. The inner part of the camera isn't painted too. So i suspect they have changed manufacturing them over time.The picture of the sensor is really interesting, thank you a lot for this! It is good to know that this sensor is sealed behind germanium. I suspect it has a similar coating than the lenses usually have? However, it doesn't look as shiny as the surface of the lens.Greetings, Hagrid

author: Ultrapurple
author_rank: Super Contributor
timestamp: August 20, 2017, 10:28:40 am
content: The early versions of the Therm-App had no grease on the threads and as a result the lenses wobbled slightly. Not enough to worry about falling out, but definitely sufficient to throw the focus off. The lens wouldn't be quite parallel to the sensor.I haven't heard of the inside being unpainted. I'd always assumed it was anodised, for strength and corrosion resistance, like the outside. Perhaps you could post a picture next time you're changing the lens?I don't know whether there is a coating on the window. I suspect so, but it's hard to tell with human eyes! The data sheet may reveal more: if anyone has a copy, could you check please?

author: Hagrid
author_rank: Contributor
timestamp: August 20, 2017, 11:21:28 am
content: I do not have another lens for the Therm-App. The 19mm seems great for most tasks. Sometimes the magnification is a bit too high, but it is okay. I have taken the lens off and made some photos of the inner part. Like you can see it is not painted. It may look a bit dirty without paint, but I would assume that everything is cleaned nicely before assembly.The other photo shows what I mentioned before. The sensor does not look as shiny as the lenses. In general terms it looks pretty darn clean, but when hold against a light source you can see this delicate structure where the light diffuses. I would guess that this is caused by the mechanical part while manufacturing the window. It would be really nice to see the data sheet, however it seems impossible to find them online.Greetings,Hagrid

author: Bruno28
author_rank: Regular Contributor
timestamp: August 20, 2017, 12:06:55 pm
content: Can the sensor be cleaned like dslr sensors? Where you physically touch with a swab.Not that I need to but I have 2 thermapp one with 6.8mm and 19mmGot the 19mm for spotting things outside and the 6.8mm for indoors. Initially I was going to get just the lens and keep swapping round when needed. But decided to get a second unit to avoid lens swap/dirt inside.Sent from my SM-G935F using Tapatalk

author: Fraser
author_rank: Super Contributor
timestamp: August 20, 2017, 12:17:08 pm
content: The window on a ULIS microbolometer is made from either Germanium or Silicon. The Microbolometers are sold with the option for either. The Germanium version has the lower NETD.Both the Germanium and Silicon windows have an AR coating to improve transmission and reduce reflection figures. The AR coating is not as resilient as that used on the Objective lens as it is no exposed to such potentially hard conditions. It should be treated with great care.The window should be dry air cleaned where possible. Oily finger prints or contamination may be removed with ether or IPA. A gentle clean with a quality microfibre cloth is safe if done with suitable care and very light pressure.Contamination of the window by large dirt or dust particles can cause weird effects on the displayed image. Hot or cool spots can appear. The cool spots are in shadow of the contamination and hot spots are caused by the contamination being heated by the Microbolometers own heat radiation acting on the contamination.If a microbolometer is calibrated with contamination on the window and the dirt is removed later, the spot where the dirt used to be will appear different to its surroundings on the displayed image.Fraser

author: Bruno28
author_rank: Regular Contributor
timestamp: August 20, 2017, 12:27:07 pm
content: Quote from: Fraser on August 20, 2017, 12:17:08 pmThanks for the detailed explanation Fraser. Once again, a encyclopedia of thermal cameras.Sent from my SM-G935F using Tapatalk

author: Fraser
author_rank: Super Contributor
timestamp: August 20, 2017, 01:08:51 pm
content: The Therm-App uses the Pico 384P-049That is the slightly poorer NETD version of the sensor.The datasheet may be found here......http://www.sofradir-ec.com/DbImages/SofEC-Pico384-v02.pdfthe Pico 384E is the higher performance version but there is not much in it in real life as lenses effect such figures anyway.Fraser

author: Bruno28
author_rank: Regular Contributor
timestamp: August 20, 2017, 01:11:29 pm
content: So these sensor can be pointed towards the sun? According to the specs...Sent from my SM-G935F using Tapatalk

author: Fraser
author_rank: Super Contributor
timestamp: August 20, 2017, 01:15:13 pm
content: Yes they are supposed to be 'Sun safe' due to the passband filtering of the suns energy. Most of the energy falls outside of the passband.I personally would not deliberately point a thermal camera at the Sun unless a lot of filtering and attenuation was in place in front of the sensor array. I consider 'Sun safe' more of a protection against accidental exposure to the Sun as it passes through the FOV, say in a CCTV installation. That would be poor installation practice though.Fraser

author: Ultrapurple
author_rank: Super Contributor
timestamp: August 20, 2017, 01:44:54 pm
content: I have accidentally pointed my Therm-Apps at the sun without lasting damage. You do get a 'hot trail' across the sensor that lasts for a while (minutes), certainly long enough for you to be thinking "oh rats, oh rats, oh rats" a few times until it fades. I definitely wouldn't recommend it and concur with Fraser's suggestion that if you are determined to try and thermal-image the sun you should do the research and have all the necessary filtering in place first.Something similar happened when I used the Therm-App to look at a toaster. You canfind the full story herebut the image below shows what happened: there was temporary 'burn-in' that lasted for long enough for me to look up burn-in (and the warranty terms!) but it all went back to normal in the end. There's also a video on that page that shows the burn-in actually happening.

author: Bruno28
author_rank: Regular Contributor
timestamp: August 20, 2017, 01:58:23 pm
content: Oh wow a simple toaster was enough to do that? I've taken a photo of a toaster and nothing happened. I also points at a friend's engine turbo which was on the 200 degrees and didn't get any burn on the sensor. Also points at a gas stove which was over 250degrees, with no sign of damage.Is there a temperature at which we should avoid pointing the thermapp at? I have the regular thermapp and thermapp TH.Also why does your pictures show all of the app buttons and not just the thermal? Also your app looks very different to mine.Sent from my SM-G935F using Tapatalk

author: Ultrapurple
author_rank: Super Contributor
timestamp: August 20, 2017, 02:12:02 pm
content: Quote from: Bruno28 on August 20, 2017, 01:58:23 pmHave a look at theFlickr pageand the description, plus the associated video.QuoteThe Therm-App technical data doesn't give any particular clues other than it's supposed to becalibratedfrom 5-90°C; given that the sensor is supposed to be sun-safe then we can infer that the upper limit is several thousand kelvin (viewed from a suitable distance), but it's not guaranteed to give an accurate temperature reading.The issue with the toaster was that it was very close; the sheer radiant heat was enough to physically heat the sensor, probably the ROIC as well, and it takes time for that heat to dissipate. It would be quicker if the sensor was mounted on a thermally stabilised platform like a Peltier system, but the power consumption would then be way over what would be acceptable for a phone. Pointing the camera at the toaster from further away and/or for a shorter time would have made an enormous difference. The amount of energy received is subject to the inverse square law, so doubling the distance quarters the heat load, but the sensed temperature would (should) remain the same. Hence my earlier comment about viewing the sun from a suitable distance.QuoteThe images were posted on Flickr in 2014. The Therm-App UI has been through several revisions since then.

author: Fraser
author_rank: Super Contributor
timestamp: August 20, 2017, 02:21:55 pm
content: As has been stated, it is the heating effect of the energy that causes image ghosts.The pixels are just thermistors and think of them as that. If you expose them to high amounts of heat energy focussed by a lens onto their faces and the die, the whole die and pixels will heat up. The pixels have a very low thermal capacity so will normally cool quite quickly, but if the die area behind them has been warmed up as well, it will radiate heat into the rear of the pixels keeping them warm for a while.No damage is done to the pixels provided they are not heated to a point where they melt or fracture !The die behind the pixels contains important electronics such as capacitors and the read out IC. Cooking these is not good for their health ! Permanent changes in components can occur if overheated. This may necessitate recalibration or may require a new microbolometer.If the sensor contains a TEC and it is heated by external thermal energy that reaches the die where the temperature is monitored, the TEC controller will drive the TEC hard in an attempt to bring the die down to around 32C. This results in high current consumption and some stress on the TEC and its drive components.Fraser

author: Bruno28
author_rank: Regular Contributor
timestamp: August 20, 2017, 09:20:49 pm
content: Thanks for the info guys. I did not think that the radiation would have heat up the sensor. But it makes sense.Sent from my SM-G935F using Tapatalk

author: Ultrapurple
author_rank: Super Contributor
timestamp: August 23, 2017, 12:25:00 pm
content: It's possible that the Therm-App I was using - an early one - used a Gen I Pico384 rather than the Gen II that I believe is more current. Unfortunately I don't have any direct information about this, but it could be that the Gen II behaves better with gross overload than the earlier version. Does anyone else have any thoughts on this? (I'm looking at Fraser...)

author: Fraser
author_rank: Super Contributor
timestamp: August 23, 2017, 10:55:05 pm
content: The Pico384P and Pico384 Gen 2 use virtually the same die. There is no performance improvement in the Gen2.The Pico384 Gen 2 is a cost and Size reduced version of the standard Pico384. It is in a surface mount package intended to aid mass manufacture of cheaper thermal imaging cameras.In daily use, you will not see any difference in the two productsI was not aware that the Gen 2 was being used in the Therm App. For the user it would not be an improvement on the standard Pico384 in any way.ULIS use the same same microbolometer die in different case formats to meet different customer needs. The operational performance is often governed by the window material and the performance of the lens block that sits in front of the sensor. The sensors are equally vulnerable to the effects of high thermal energy exposure heating of the die via the lens. It is just physics as no heat shield or vacuum cam totally prevent radiant heating of the area around the pixels. Energy source and proximity to the camera lens dictates the localised heating effect.Fraser

author: Bruno28
author_rank: Regular Contributor
timestamp: August 24, 2017, 01:24:17 am
content: I got myself one of those flir C2 for a pretty good price. Always wanted one. But I'm sure I'll be selling now that ive compared to thermapp and had the mental relief of owning it.Here is a Flir C2 (in thermal mode only) vs a Thermapp TH.It's cool that the C2 is small and pocketable. But they need a resolution bump.Sent from my SM-G935F using Tapatalk

author: Ultrapurple
author_rank: Super Contributor
timestamp: August 24, 2017, 08:22:33 am
content: Wow, those images are very informative - thanks.I think you've hit the nail on the head that the C2 'just works' whereas you have to faff around with the Therm-App (much as I like it, it is a mild pain having to connect it all up every time - but compared to its liquid nitrogen-cooled ancestors I guess we don't know we're born!).The first and last images are particularly telling. May I invite you to post them on theFlickr Therm-App Users group, with a brief explanation of what you were doing? (All other Therm-App related images are welcome there of course, along with relevant comments).My apologies if 'touting' other relevant sites isinfra dig: please, someone, let me know if thisisthe case.

author: Bruno28
author_rank: Regular Contributor
timestamp: August 24, 2017, 09:49:15 am
content: I can try. But from the app it does not allow me to post photos or even seen the discussionsSent from my SM-G935F using Tapatalk

author: Ultrapurple
author_rank: Super Contributor
timestamp: August 24, 2017, 03:00:42 pm
content: I don't use the Flickr app because I find it very limiting.You should be able to see the images and discussions if you use the web interface. As is customary, only members of the group canpostimages and discussions.If you're still having problems after trying the web interface, PM me.