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B 4. Pyrgeometers
B 4.1 Eppley Precision Infrared Radiometer (PIR)
This pyrgeometer is a development of the Eppley Precision Spectral Pyranometer. It is intended for
unidirectional operation in the measurement, separately, of incoming or outgoing terrestrial radiation as
distinct from net long-wave flux. This instrument comprises the same type of wirewound-plated thermopile
detector and cast bronze desiccated case as the PSP. Temperature compensation of detector response
is likewise incorporated. Radiation emitted by the detector in its corresponding orientation is automatically
compensated, eliminating that portion of the signal. A battery voltage, precisely controlled by a thermistor
which senses detector temperature continuously, is introduced into the principle electrical circuit.
Another innovation is aimed at isolating infrared radiation from solar short-wave radiation in daytim e. This
is accomplished by replacing the glass hemispherical system of the pyranometer with a silicon hemisphere.
On the inner surface, there is a vacuum-deposited interference filter. The transmission range of the
pyrgeometer window is approximately 3.5-50 :m.
A calibration certificate and a wiring diagram are included.
Specifications
Sensitivity: approx. 4 :V W m
-1 2
Impedance: approx. 700 S.
Temperature Dependence: ±1 % over ambient temp. range -20 to +40 °C.
Linearity: ±1 % from 0 to 700 W m
-2
Response time: 2 seconds (1/e signal).
Cosine: better than 5% from normalization, insignificant for a diffuse
source.
Mechanical Vibration: tested up to 20 g's without damage.
Calibration: blackbody reference.
Size: 5.75 inch diameter, 3.5 inches high.
Weight: 7 pounds
Orientation: Performance is not affected by orientation or tilt.
Temperature Measurement Thermistor YSI 44031
Specification for ventilator
Input Power: 110 - 120 V, 60 Hz (or other specified supply).
Output: approx. 30 CFM.
Size: 8 inch diameter, 5.75 inches high.
Weight: 5.5 pounds.
B 4.2 Eko MS-201 Precision Pyrgeometer
For measurement of long wave radiation, beyond 3 :m.
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