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Advice on reading thermal images

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Well & Truly Off The Grid

Last Post by robl 2 years ago

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Mars

(@editor)

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Topic starter 15/03/2022 3:11 pm

Using the thermal imaging camera was really helpful. We've found a few areas that require some minor work. Generally, we've been very pleased with the insulation work we've done. The colours aren't always that important – it depends on what you're targeting on.

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heat-pump-newbie

(@heat-pump-newbie)

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04/04/2022 11:39 am

@editor Which Flir model was it you used ? I've been thinking about getting the 'cheap' one Flir One Gen 3 with resolution of 60 x 80.

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Mars

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Topic starter 04/04/2022 11:48 am

@heat-pump-newbie, we used this model (FLIR ONE iOS) and it was excellent – a tad pricy, but very, very helpful:

https://www.amazon.co.uk/Thermal-Imaging-Resolution-Lightning-Connector/dp/B0728C7KND?crid=7S5KFZ845SOJ&keywords=flir%2Bone&qid=1647293136&sprefix=flir%2Bone%2Caps%2C164&sr=8-5&th=1&linkCode=ll1&tag=myhomefarm-21&linkId=389091cd25d1477537c1cca37873c51b&language=en_GB&ref_=as_li_ss_tl

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robl

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05/04/2022 5:50 pm

@editor

I use my companies Flir camera - I think it's E40, or something like that. It was pricey (£5k), but that was ages ago, they're all much cheaper now. It's best when it's dark and cloudy and cold - the sun heats objects up, and the night sky is very cold so things unevenly cool down if they can "see" it. When it's cold you get better contrast. I think the more expensive cameras have manual focus, bigger aperture, so lower noise, the work one is 50fps - not needed for my "non work activities"!

I tend to let the camera autorange first, then "lock it off", fixing the Tmin and Tmax of the display, so as I walk around the colours don't change their meaning. I like the colour bar on the side for easy reference later.

Here's a pic I took of a friends house recently. I've labelled the walls a(left gable), b(above campervan), c(right hand side):

a) cavity wall insulated

b) rendered cavity wall. Don't think they filled the cavity, hence glowing.

c) wooden slats over cavity wall. Don't think they filled cavity. It looks like it is ok - but cold air will be circulating behind the cladding, so the pic "lies".

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heat-pump-newbie

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05/04/2022 7:23 pm

@robl I have an Fluke IR thermometer which is great unless the scanned surface is shiny, like a copper pipe... Would the Flir have trouble giving a meaningful thermal picture of shiny pipes etc, eg foil covered lagging ? I'm hoping to get a good idea of how well the lagging is performing.

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robl

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05/04/2022 8:03 pm

@heat-pump-newbie

Yes, just as you say it’s terrible with metal surfaces. You can sometimes program in the emissivity, I think ‘mine’ defaults to 0.95. An emissivity 0.95 means 95% of the reading will be of the surface, and 5% is a reflection. Reprogramming the units 0.95 value just changes how the camera interprets the amount of 10um radiation hitting it, it won’t alter the picture itself. If it’s a shiny surface, like a window, you’ll still see images in the reflections, and you won’t see through it or walls, not like in the movies!. I think clean metal is so low emissivity as to be pointless - stick anything on it and it will be ok - pvc tape, paper, paint, dirt.

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