For a project I need to measure the night sky radiation, since most of it is infrared I need a infrared radiation sensor that can detect that wavelength range and that can pick up the low intensity of the night radiation. I just need the value of W/m2 at any certain time of the night.
I'm having trouble finding a sensor since every one i've found is either for the visible range (400 to 800 nm, there was a great thread in this forum but it was for that wavelength range only) or are motion detectors and apparently don't show the radiation intensity.
I don't need high accuracy so a cheap device that I can connect to my arduino is totally fine. I have a arduino uno.
You could use the Swinbank formula, in which case you'd need a regular ol' thermometer, a sensor for relative humidity, some image processing to estimate the percent of cloud cover, and a way of scraping a weather service web page for cloud height.
Or, use an infrared thermometer and the Stefan-Boltzmann law to estimate the energy flux.
Better yet, do both and see how close the results are. Even if you don't implement the Swinbank method (which would be challenging to automate), you should do it "by hand" a few times to check the other method.
If they're within a factor of two, you're probably doing good.....
Are you looking for the IR radiation from the air molecules, including water vapor or are you looking for the reflected radiation from the earth or both? Are you looking for earth radiation reflected from clouds?
jremington:
Define "that wavelength range". The term infrared covers a large region of the spectrum.
The ideal range would be the same range a pyrgeometer can pick up (roughly between 4 and 40 micrometers) but if that's not possible it could be thinned down to between 8 and 15 micrometers (again, roughly).
el_supremo: This thread might have useful info - it mentions the MLX90614.
Pete
Apparently this delivers remote temperature by measuring the IR radiation, but I need the radiation in W/m2. Can it be programmed to deliver the radiation instead of the temperature?
Paul_KD7HB:
Are you looking for the IR radiation from the air molecules, including water vapor or are you looking for the reflected radiation from the earth or both? Are you looking for earth radiation reflected from clouds?
Paul
I need to measure all the IR radiation that gets to the ground at night regardless of where it comes from
Apparently this delivers remote temperature by measuring the IR radiation, but I need the radiation in W/m2. Can it be programmed to deliver the radiation instead of the temperature?
The "temperature" is the radiation. How you use that information is up to how you write the program.
I need to measure all the IR radiation that gets to the ground at night regardless of where it comes from
It is clear from your comments that you have little understanding how this is done. Given that state of affairs, you have two choices:
(1) buy the expensive commercial equipment that does this for you, or
(2) learn a bit about the theory and how radiation flux is measured, which in turn will lead you to how approximate measures of the radiation flux can be made cheaply.
I've been looking into what seems a similar topic: PAR (photosynthesis active radiation). This also attempts to measure a photo flux over a certain range.
One of the major problems is that you basically need a spectrum analyser, as you need to know what wavelengths you get to calculate the actual energy of the photos. In IR you have the same problem: higher wavelength photons have less energy than lower wavelength.
Brightness measures the number of photons, not their energy.
Temperature is for IR probably the closest to what you're trying to measure, though it'll still output a single number, and it may still be brightness based. You'd have to research the actual method used by the sensors to determine if, and if so, how, it can be converted into your desired flux.
Your advantage over PAR is of course that you want the full spectrum, not a very specific part of it. That should make it easier.
Moonlight is 500 µW/m2 ? The infrared part will be a lot less than that.
You are low by about 6 orders of magnitude.
In fact, the night sky downward radiation flux is 200-350 Watts/m2, depending on the sky and cloud cover temperature. This can be [estimated quite simply](http://The infrared part will be a lot less than that.) from the Stefan-Boltzmann law.