240-8101 Star Pyranometer 
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| 240-8101 Star Pyranometer | 240-8106 Protective Housing |
The Model 240-8101 Star Pyranometer is a basic instrument for measuring direct and diffuse solar radiation (global radiation). The sensing element is composed of 12 wedge-shaped, thin copper sectors arranged radially, 6 white alternating with 6 black. Six chromel-constantan thermocouples are embedded in each sector to produce a 72 junction thermopile. Output from the thermopile is approximately 15µV/Wm². The white sectors of the sensing element are painted with a Kodak paint that yields an almost perfect reflective surface. The black sectors are painted a highly absorbent flat black. When the sensor is exposed to solar radiation, a temperature difference is created between the black and white sectors. This temperature difference is proportional to the radiation intensity and is not affected by ambient temperature.
The windshield protecting the sensor is a 2.75" diameter, polished crystal glass dome which admits electromagnetic radiation between 0.3 and 3 microns. The highly reflective outer surface, along with the mass of the case, keeps the case interior at ambient temperature. Instrument leveling is accomplished by means of a bull's-eye level and three leveling feet.
When used in conjunction with an optional shadow band, the star pyranometer will measure diffuse solar radiation. Direct radiation can be measured using two star pyranometers: one, with a shadow band, to measure diffuse radiation and a second, without the shadow band, to measure both direct and diffuse. The difference between the two measurements is direct radiation.
The Model 240-8106 Protective Housing uses a ventilator to blow air from the bottom to the top of the star pyranometer, keeping the glass dome free of condensation, dew, and rain. In addition, there is an electric heater that turns on at approximately +10°C (+50°F) which assists in keeping the glass dome clear when it snows. This unit will help keep maintenance to a low level. The glass dome must be kept clean at all times to provide accurate readings. The unit requires 24 Vac at 80 Va for proper operation.
Specifications
Sensing Element 12 black & white copper segments with 6 thermocouples each
Spectral sensitivity: 0.3 to 3 µm
Azimuth response: < 3% of the value
Cosine response: < 3% of the value, zenith angle 0° - 80°
Response time: < 25 seconds @ 95%, < 45 seconds @ 99%
Measuring range: 0 to 1500 Wm²
Resolution: < 1 Wm²
Stability: < 1% per year (temporary operation)
Temperature effect: < 1% of the value between -20°C to +40°C
Linearity: < 0.5% in the range 0.5-1330 Wm²
Impedance: About 35 ohm
Output: About 15 µV/Wm² or 4-20 mA = 0-1500 Wm²
Ambient temperature: -40°C to +60°C / -40°F to +140°F
Size: 5.4" dia x 3.6"h
Weight/shipping: 1.9 lbs/4 lbs
Ordering Information
240-8101 Star Pyranometer (mV output), with 3 meters cable
240-8102 Star Pyranometer (4-20mA output), with 3 meters cable
240-153-8101 Tower Mount, 12" boom with tower mounting hardware
240-153-8106 Tower Mount, 22" boom with tower mounting hardware
240-8101-C Additional Cable, per meter
240-8101-D Glass Dome
240-8101-OR O-Rings, set of 3
240-8101-SG Silica Gel, 100 grams
240-8101-SGC Silica Gel Container, filled
240-8106 Protective Housing, 24 Vac
240-8106PS Power Adapter for 240-8106, 220 Vac to 24 Vac
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Solar Radiation Sensors
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