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Some thermal clips

One on top of two

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What you are calling positive and negative is known as white hot and black hot in thermal terminology and it is what it says.

In white hot mode, hotter objects appear white and in black hot mode, hotter objects appear black

There are also various colour modes where a temperature (or small range of temperature) is displayed as a specific colour.

This colour presentation looks very clever and attractive to those who are not au fait with thermal imagers, but in reality, white hot and black hot provide a much more detailed image than any of the colour modes because the number of colours used is small (typically 16) while most thermals will display 256 discreet levels of grey between pure black and pure white.





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Lines per millimetre, or more accurately line pairs per millimetre, is a resolution measurement system that has its genesis in old analog tubed NV systems.

When applied to digital imaging systems (NV or thermal) it doesn't really produce a sensible number.

If you want to know the the size of the smallest thing a digital imaging system can detect at (say) a distance of 100m),  then simply divide the pixel size by the focal length of the objective lens and multiply the answer by 100

So, in the case of the Helion 2 XP50 pro, the pixel size is 17 microns, the focal length is 50mm.

Therefore, at a range of 100m, one pixel "sees" a square whose sides are (17/50)*100 = 34mm

The smaller that number, the more detailed the image will be.

Note that the number of pixels in the sensor does affect the resolution, only the pixel size and lens focal length

The 1024 (1024x768) you mention in your reply above is the number of pixels in the display, which has no effect on the resolution of the system as long as there are at least as many pixels in the display as there are in the sensor

Having said all that, there are other thermal imagers available which also have sensors with 17 micron pixels and 50mm lenses which will have the same resolution as the OPs images - but the image quality will not be anything like as good as those above.

Most thermal imager specifications quote something called NETD

This stands for Nett Equivalent Temperature Difference and is a measure of the smallest change in temperature that the lens/sensor system can detect.

Typical NETD values are 50mK ( degrees millikelvin) - so 50mK is 0.05 degrees centigrade

The Pulsar Helion2 XP50 Pro has an NETD of 20mK making it capable of detecting much smaller changes in temperature than virtually all other hand held thermal imagers.

This very small NETD allows more temperature detail to be observed and this, combined with Pulsars very sophisticated signal processing result in the high quality images above





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It's very impressive technology.  I recall back in the 1980's having to lug a thermal camera around the factory checking for electrical 'hot spots'. That needed liquid nitrogen to cool the sensor.  We thought that was a great bit of kit,  how times change - I wonder how the sensor is temperature referenced in the modern kit?

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