Infrared pics following "Found some horrible plumbing, comments welcome" thread

Discussion in 'Plumbers' Talk' started by BikerChris, Jan 12, 2020.

  1. Sparkielev

    Sparkielev Screwfix Select

    How about after a vindaloo !
  2. BikerChris

    BikerChris Active Member

    Probably the same, just body is turned around :)
    Hans_25 and Sparkielev like this.
  3. CraigMcK

    CraigMcK Screwfix Select

    Interesting, one of the pictures of the house looks like you can see what’s inside, through the glass. True thermal image cameras can’t see through glass/clear plastic
  4. BikerChris

    BikerChris Active Member

    Yeah I think it is the cheapest one you can get, it also shows the reflection of heat as well, so if I take a pic and I'm in the pic, you can see my heat
  5. CraigMcK

    CraigMcK Screwfix Select

    Heat reflections are quite common, part of the skill of thermography is making sure it’s not a reflection you are seeing.

    Things that are visually reflective tend to be thermally reflective too.

    The other challenge is understanding every surface has the potential of a different emissivity, so even surfaces that are the same temperature can appear in the image to be different.

    That’s why cheap surveys can do more harm than good if the operator has not been trained properly. The house owner looks at the images and equally just sees different colours and thinks they need a new roof or new windows.

    From the electrical side I see it all the time, somebody takes a picture of a consumer unit and says look that MCB is much hotter than the others. The reality is that one has a higher load than the others and may well be perfectly normal.
    Changing the colour scale is also a good way to panic someone
    BikerChris likes this.
  6. BikerChris

    BikerChris Active Member

    you're quite right Craig, I've been playing about with it now for a good dozen hours and it's easy to pick up on the obvious things. I see threshold strips show up 'hot' when it's just because they are reflective. Like you said, I've pointed it at slightly reflective things and can clearly see myself, so I view it off-angle instead. The more technical things I'm sure only come with practice or some sort of course.

    It reminds me of moisture meters actually - stick one on a wall of concern and people would panic, but stick it in an adjacent wall for comparison and you get a better picture. Did this with a failed shower a few months ago, worked a treat and avoided hacking off more tiles than needed.

    Funnily enough I was going to comment on the electrical side, consumer units are likely to get a bit warm really, but there probably isn't a reg that says they should not exceed X degrees celcius!

    I can see them being used to scare people into spending money though, just costs a lot more than a moisture meter.

    The one I borrowed has been quite handy though, completely confirmed that there is a heat leak from my neighbours house into mine. Yes it's free energy, but it's also followed by air bourne noise which I don't want...or want to give :)
  7. DIY0001

    DIY0001 Active Member

    Well that depends on the plastic and, in some cases, the glass.

    I've mentioned before on this forum that designing thermal imagers is my day job, so I know quite a bit about this topic.

    Basically there are two types of thermal imaging camera, based on bolometers and photon detectors, and there are two wavebands that they work in - 3-5microns (roughly 10x the wavelength of visible light) and 8-12microns (roughly 20x the wavelength of visible light). At terrestrial temperatures there is about 20x more energy in the 8-12band than in the 3-5band.

    The OP's camera was a bolometer type working in the 8-12band, with a sensitivity of about 1/10th of a degree centigrade; it isn't sensitive enough to work well in the 3-5band. Photon detectors are needed to get decent performance in 3-5, and can easily have sensitivities of 1/100th of a degree centigrade or better, however they need to be cooled, often to almost -200degC. Cooling, and its resulting design complications, make photon sensitive cameras 100 - 1000x more expensive than bolometer cameras which can operate without any cooling.

    Both 3-5 and 8-12 bands are transmitted by many plastics, such as polythene, but blocked by others, such as polycarbonate, while some plastics like melamine transmit 3-5 but not 8-12.

    What the material doesn't transmit, it either absorbs or reflects. If it absorbs then it gets warmer itself until it emits as much energy as it absorbs. So a material that doesn't transmit or get warm has to reflect, which is what the appropriate glass or plastics do.

    If you view a plastic carrier bag with the bolometer camera then you will almost certainly see straight through the bag at what is inside. Almost certain because the bag may have a coating or printing on it that is absorbent. If it absorbs then the printing will appear slightly warmer than the surroundings.

    Most glass blocks both bands as well, however high silicate crown glass will transmit 3-5 at around 50%/mm whilst less than 1mm thick glass will completely block 8-12, resulting in almost mirror-like reflection.
    Things worth trying while you have the camera.

    Put your arm in a black bin liner and ask someone whether your hand is open or in a fist. They can't tell by eye because the plastic is black, but the thermal camera sees straight through the bin liner showing whether your hand is open or closed. Similarly, but probably not for this time of year, the light synthetic fabrics most people wear on a summer's day have exactly the same effect! :cool: Watch out for pervs roaming beaches with thermal imagers. :eek:

    Another one is to get a thick book, like a phone book or a bible. Put your hand on the outer cover for a minute or so. Then after removing your hand, turn the pages inside and view the thermal imprint of your handprint passing through the book. If you time the turning of the pages right you can "surf the wave" as the heat from your handprint propagates through the book.
    Last edited: Jan 15, 2020
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  8. CraigMcK

    CraigMcK Screwfix Select

    I've done both the level 1 & level 2 thermography course from Flir. I think the first course was 3 days and level 2 was 5 with a fairly challenging exam at the end.

    There are limits for consumer units, they are set within the standard (61439-3) However that is a type test and not real life. Part of the test is knowing how much current is flowing in each circuit. Real life examples don't offer that option, in most cases, so it's all a bit of a guess. That is unless, there is a significant figure shown where a loose connection me be sitting. But on the day you do it, there is no current in that circuit, so it doesn't show up. That night the heaters come on and burn the house down... extreme I know, but it's what you would need to consider as part of the full inspection process that your liability insurance needs to cover.

    The one thing you need to watch for when viewing images it to try and fix the upper/lower temp colour range, it can get confusing very quickly looking over images on a colour basis to then realise red on one is 80C and on another its 30C because the camera has auto ranged.

    If you are planning to go into reporting the Flir free report software is quite good and you can add new temp points or rescale the range from the imported image.

    For anyone that's not seen thermal reflections, this is an image on a whiteboard, which was at room temperature, you can see the person taking the image on the shot, but not visually on the board itself. The high temp is just Phantom data based on the highly reflective surface.

  9. BikerChris

    BikerChris Active Member

    Wow, well done guys for saying so much, who would think it that both someone who designs infra red cameras and someone that has been on a flir course would be on here at the same time. it is really interesting to know there are different levels of infrared ness, I did see an option on there about a certain temp range it would do, i forget now, if I can borrow it again i will. I will try the arm in a bag test to see what happens, that will be interesting! surely pervs cant afford decent thermal imagers...mind you, from what you read in the papers and all that!

    I will also try that book test, i have seen that when i am walking around a carpet with just socks on i can see my foot prints, same happens on a table. didnt try it with a glass table though, wonder what would happen - guess i'll see next time!
    Craig, that is interesting and thank you for putting it simply for me and anyone else reading, very interesting and although i am not a spark (far from it) i can roughly see what you mean about the house burning down. you are spot on about that auto range thing, i did see an option to fix it, so that would be a good thing to do, fix it?

    i don't think i would be able to afford a decent infrared camera + Flir course and not sure i could recover cost back by doing reports and that, but it is an interesting area. like you said, the info could be used wrong, I am lucky that I know my house and can easily see where heat from next door is coming into my gaff. I am going to show them the pics soon and have a chat, because as well as heat we are getting a lot of noise - the infrared is handy to prove it!

    sorry for the delaying replying by the way, ton of things went wrong lately, fence fell over in gales, central heating system went wrong, window leaked...not a good week :(

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