[pic of David Brooks’ photometer kit]
In following up on his discussion, on the last episode on Make: Talk, of building Sun Photometers and measuring total column water vapor, Forrest Mims sent me the following info:
The instrument that measures total column water vapor is a sun photometer with LEDs that detect at 940 nm (water vapor absorption band) and 820 nm (reference band). I’ve never published the circuit for this specific instrument, which I first developed in 1989, for it is identical to a standard LED sun photometer.
Here is some online material:
1. My initial paper on using LEDs for sun photometry is here [PDF]
2. Detailed construction plans for an NSF-sponsored version of my LED sun photometer (1-channel) can be found here.
3. Detailed assembly steps for building a GLOBE sun photometer available as a kit from David Brooks.
4. Detailed protocol on the operation and use of the GLOBE near-infrared sun photometer for measuring total column water vapor can be found here.