 3120
Silicon Cell Pyranometer
Description
Rugged and weatherproof, the Model 3120 Silicon Cell Pyranometer measures
global solar radiation. When used with the Model 3079 shadow ring, it will
measure diffuse radiation. This pyranometer is low cost, lightweight, and
easy to install.
The sensor is a silicon photovoltaic cell which absorbs radiation from 0.35
to 1.15 microns. The silicon cell converts this light energy directly into
electrical energy, and the output voltage (approximately 70 mV/W/m2) is essentially
linear with light intensity. Full-scale response time is less than 1 millisecond
due to the fact that the instrument is light sensitive, not heat sensitive
as the thermopile pyranometers are. If the output is integrated over a daily
period, the accuracy of the value is within +/-3%. Accuracy of instantaneous
values is +/-5%. Temperature compensation is provided from 4° to 60°C.
Features
A pyrex glass dome protects the silicon cell from wind and moisture. Desiccant
is included to prevent moisture condensation on the inside of the glass. A
10' length of cable is provided. The positive output lead is connected internally
to chassis ground, therefore requiring isolation at the mounting hardware.
The Model 30318 mast adapter provides the needed isolation.
Shadow Ring
Description
The Model 3079 shadow ring is used with a pyranometer for measurement of
diffuse sky radiation. The shadow ring prevents direct solar radiation from
reaching the pyranometer. If used in conjunction with a second pyranometer
without a shadow ring, direct radiation can be calculated by finding the difference
between the two pyranometer measurements.
Features
A platform at the center of the ring supports the pyranometer in a level
position. Adjustments are provided for shadow ring leveling and for orientation
according to latitude and sun declination
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