Sun Photometer

ATMS 360 Atmospheric Instrumentation (return to main page).

Sun photometer details.

(This is an instrument in GLOBE, Global Learning and Observations to Benefit the Environment)
(See also the HAZE SPAN project).

Forrest Mims sun photometer in a VHS case.
LED as a detector, as VERY NICE student project. LED as a detector.
Photodiode theory, from those who are in the business and know what they are talking about.
NASA's sun photometer network (AERONET).

How to build the sun photometer in a VHS case.


Figure 1. Sun photometer circuit. From OpAmp theory,terminals 2 and 3 are at ground potential, and no current flows through these pins. The current i produced by the LED when light shines on it is simply related by Ohm's law as Vout = i * R, so 1 microampere current produces 1 Volt when a voltmeter is placed between Vout and the Ground Terminal.	Figure 2. Photograph of our 1 channel prototype LED sun photometer at 660 nm(wavelengths 430 nm, 470 nm, 530 nm, 660 nm, 870 nm, and 950 nm have been used on various versions.) See also linearity tests, and the description of our 14 units, and a lab report discussing the instrument.