Re: [Phys-L] Absorption and Scattering of IR By CO2 Gas
I can think of two important issues off-hand with re-creating a demo like
this.
1) If you use glass for the ends of your container, then the glass will
absorb the IR and it won't get through, making the image always dark.
2) CO2 only absorbs a couple of fairly narrow bands of IR, notably around
15 um. If your camera detects a broad range of IR, then only a fairly
small fraction of the IR will get absorbed, and the image will only dim
slightly, even with a long tube full of CO2.
And since most cameras would be designed to see THROUGH the atmosphere,
they are probably designed to operate AWAY from the bands that CO2 and H2O
absorb.
Tim
On Tue, Jul 30, 2024 at 9:55 AM Zani, Gerald via Phys-l <
phys-l@mail.phys-l.org> wrote:
> Dear Tap-l,
>
> We have a FLIR IR thermal camera and want to use it to show that CO2 gas
> absorbs IR.
>
> Does anyone do this?
> How?
>
> For our demo, we made a tank and filled it with CO2 gas, as shown in this
> video:
> https://www.youtube.com/watch?v=Ot5n9m4whaw&ab_channel=m1der1
>
> But we are having a problem.
>
> It might be due to the default setting for the thermal camera, which is for
> automatic thermal tuning?
> If So, then when the image gets dimmer due to the IR light scattering by
> the CO2 gas, the camera is automatically tuning the thermal span and the
> thermal level. This defeats the demo. It appears that the CO2 is not
> scattering the light.
>
> To prevent this problem, we must go into the camera menu to adjust the
> brightness of a FLIR thermal camera so it has a manual setting, not
> automatic and we need to find the thermal cameras Temperature Scale
> settings, which have a span and a level.
>
> We need to change the temperature scale, the temperature span and the
> temperature level. This process is called thermal tuning.
>
> Does anyone know how to do this?
>
> Thanks,
> - JZ
>
> --
> Gerald Zani
> Senior Engineering Technician
> Brown University School of Engineering
> (401) 863-9571
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> Phys-l@mail.phys-l.org
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