PRECISION INFRARED RADIOMETER

Model PIR

The Precision Infrared Radiometer, Pyrgeometer, is intended for unidirectional operation in the measurement, separately, of incoming or outgoing terrestrial radiation as distinct from net long-wave flux. The PIR comprises a circular multi-junction wire-wound Eppley thermopile which has the ability to withstand severe mechanical vibration and shock. Its receiver is coated with Parson's black lacquer (non-wavelength selective absorption). Temperature compensation of detector response is 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.

Isolation of long-wave radiation from solar short-wave radiation in daytime is accomplished by using a silicone dome. The inner surface of this hemisphere has a vacuum-deposited interference filter with a transmission range of approximately 3.5 to 50 µm.

SPECIFICATIONS

• Sensitivity: approx. 4 µV/Wm^-2.
• Impedance: approx. 700 Ohms.
• Temperature Dependence: ±1% over ambient temperature range -20 to +40°C.
• Linearity: ±1% from 0 to 700 Wm^-2.
• Response time: 2 seconds (1/e signal).
• Cosine: better than 5%.
• 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.