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| Flir Thermal Camera Question |
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| Berni:
Yep we do have radio wave cameras. A common example of that is phased array radar, pretty common these days on cars. Since most things you want to see with it don't emit any appropriate freqency radio waves (nor does the sun in any reasonable amount) they also integrate an "iluminator" into the same device that shines a focused beam of RF for illuminating the targets. This also has the benefit that the radar receiver can phase lock onto the transmitting RF and get a much improves SNR. We can't really build a camera the classical way with a lens and detector array in RF because the wavelengths are so long that the camera would be impractically huge. But what a camera essentially does is simply detect light with a very good angular resolution, something that a phased array can do too. The concept can go even lower in frequency in making a "sound camera" using a array of microphones that can precisely determine the direction of sound waves down to sub degree precision, the amplitude can then be mapped to a heatmap to create an image. But obviously don't expect a very high resolution image as the wavelengths are too long to see small objects, weird wave diffraction effects come into play (much like small features turns visible light into a rainbow, messing up your ability to properly see things smaller than 1 micron) We also have so called radio telescopes. They connected the huge dishes around the world together to create a phased array the size of the earth, giving it a very high angular resolution so that they can actually image something far far away. Tho the dishes aren't actually physically connected, they just are synchronized by GPS and record the radio signal onto hard drives, these then get brought to a supercomputer that combines the signals together. |
| bostonman:
I believe the answer is obvious, but seems hard to believe. If I touch something, say a wall, and aim the thermal camera on the spot I touched, I can see my hand print. The obvious is that the heat from my hand remains on the wall and therefore being picked up by the camera. The baffling part is how long the imprint remains on the wall. Am I correct in thinking the hand print is the heat that transferred from my body to the wall (the cold wall pulling heat out of my body) or is it something else? Also, why does it last so long? Seems the large wall would dissipate heat very quickly and the hand print would vanish. |
| Bill W:
--- Quote from: bostonman on December 31, 2024, 02:54:56 am ---I believe the answer is obvious, but seems hard to believe. If I touch something, say a wall, and aim the thermal camera on the spot I touched, I can see my hand print. The obvious is that the heat from my hand remains on the wall and therefore being picked up by the camera. The baffling part is how long the imprint remains on the wall. Am I correct in thinking the hand print is the heat that transferred from my body to the wall (the cold wall pulling heat out of my body) or is it something else? Also, why does it last so long? Seems the large wall would dissipate heat very quickly and the hand print would vanish. --- End quote --- One of the standard thermal 'party tricks'. Yes the heated area of paint / wallpaper does stay warm that long. Do note though - 1 - it is only the surface you heat up. Not the wall. 2 - walls should be fairly poor conductors of heat for their normal function. Try matt painted metal and the handprint does not last. 3 - assuming your hand gets the surface to 30°C (ambient+10°C) then the print will still be visible down to ambient + 0.1°C |
| bostonman:
That's amazing. I've touched objects for a second or two and amazed how long the hand print remains visible with the camera. --- Quote --- it is only the surface you heat up. Not the wall. --- End quote --- The surface is transferring the heat though to the wall, correct? First I touch the surface and then slowly the wall is transferring heat away from the surface into the wall. In a perfect insulated room/house, I should be able to bring the wall to equal temperature with my body over a long period of time. |
| Bill W:
--- Quote from: bostonman on December 31, 2024, 03:46:34 pm ---That's amazing. I've touched objects for a second or two and amazed how long the hand print remains visible with the camera. --- Quote --- it is only the surface you heat up. Not the wall. --- End quote --- The surface is transferring the heat though to the wall, correct? First I touch the surface and then slowly the wall is transferring heat away from the surface into the wall. In a perfect insulated room/house, I should be able to bring the wall to equal temperature with my body over a long period of time. --- End quote --- In that ideal circumstance then yes. The camera only ever sees the surface temperature. What goes on beyond is thermodynamics not imaging How much heat goes into your wall depends on its' thermal conductivity and its' thermal capacity. Wallpaper - polystyrene - plaster - cinder or wallpaper - plasterboard - mineral fibre is going to heat up on the surface faster and drain away a lot slower than say a paint on concrete. |
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