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.

Specification sheet for Linear Technology 1006 Operational Amplifier used in the sun photometer circuit, and of another Op Amp, LF351.

Golden rules for Operational Amplifiers (helps to understand, perhaps,

the way the transimpedance amplifier works on the LED sun photometer.)

LED treatment in general. LED as a detector.

Sun photometer links.

Some theory.

Applications, hardware 1, 2, 3.

Forrest Mims papers on Sun Photometry.

Mims III, F. M. (1992). ³Sun Photometer with Light-Emitting Diodes as
Spectrally Selective Detectors.² Appl. Opt. 31, 6965-6967

Mims III, F. M. (1999). ³An International Haze-Monitoring Network for
Students.² Bulletin of the American Meteorological Society 80,

Mims III, F. M. (2002). ³An Inexpensive and Stable LED Sun Photometer
for Measuring the Water Vapor Column over South Texas from 1990 to 2001.²
Geophys. Res. Lett. 29, DOI 10 1029/2002GLO14776.

Mims III, F. M. (2003). ³Solar Aureoles Caused by Dust, Smoke, and
Haze.² Appl. Opt. 42, 492-496.

Mims, S. A. and F. M. Mims III (2004). ³Fungal Spores Are Transported
Long Distances in Smoke from Biomass Fires.² Atmos. Environ. 38, 651-655.

The following paper will appears in due course.

Mims III, F. M. (2000). ³Solar Radiometer with Light-Emitting Diodes
Spectrally-Selective Detectors.² Opt. Photon. News 11, S3-S4.