PRECISION SPECTRAL PYRANOMETER 日照强度计
The Precision Spectral Pyranometer is a World Meteorological Organization First Class Radiometer designed for the measurement of sun and sky radiation, totally or in defined broad wavelength bands. It 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). This instrument is supplied with a pair of removable precision ground and polished hemispheres of Schott optical glass. Both hemispheres are made of clear WG295 glass which is uniformly transparent to energy between 0.285 to 2.8μm. For special applications, other Schott glasses and Infrasil II quartz hemispheres are available. Included is a spirit level, adjustable leveling screws and a desiccator which can be readily inspected. The instrument has a cast bronze body with a white enameled guard disk (shield) and comes with a transit/storage case. A calibration certificate traceable to the World Radiation Reference and a temperature compensation curve is included.
PRECISION INFRARED RADIOMETER 红外辐射计
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.
TOTAL ULTRAVIOLET RADIOMETER 紫外辐射计
The Total Ultraviolet Radiometer is a rugged, relatively simple detector for the measurement of solar UV radiation. Ease of operation combined with performance accuracy comparable with pyranometers intended for the recording of the total short-wave radiation (0.295 to 0.385 μm) make this instrument an attractive instrument for UV measurement.
This instrument utilizes a hermetically sealed selenium barrier-layer cell which is protected by a quartz window. It is operated at low light levels and under conditions of minimum electrical current drain, in order to ensure a high degree of performance stability over lengthy periods of exposure. A specially designed teflon diffuser not only reduces the radiant flux to acceptable levels but also provides close adherence to the Lambert cosine law. An encapsulated narrow bandpass (interference) filter limits the spectral response of the photocell to the wavelength interval 0.295 to 0.385 μm, with negligible secondary transmission.
The unit is of brass construction and includes adjustable leveling screws and a circular spirit level
A calibration certificate traceable to the National Institute of Standards and Technology (NIST) is included.
NORMAL INCIDENCE PYRHELIOMETER 直射辐射计
The Eppley Normal Incidence Pyrheliometer is a World Meteorological Organization First Class Pyrheliometer designed, as its name implies, for the measurement of solar radiation at normal incidence.
The NIP incorporates a wire-wound thermopile at the base of a tube, the aperature of which bears a ratio to its length of 1 to 10, subtending an angle of 5°43'30". The inside of this brass tube is blackened and suitably diaphragmed. The tube is filled with dry air at atmospheric pressure and sealed at the viewing end by an insert carrying a 1 mm thick, Infrasil II window. Two flanges, one at each end of the tube, are provided with a sighting arrangement for aiming the pyrheliometer directly at the sun. A manually rotatable wheel (not shown) which can accommodate three filters, while leaving one aperature free, is provided.
The pyrheliometer is mounted on a power-driven equatorial mount for continuous readings. Please see Solar Trackers.
A calibration certificate traceable to the World Radiation Reference and a temperature compensation curve are included.
SOLAR TRACKERS 太阳跟踪器
Models SMT-3, ST-1, ST-3
The Eppley Laboratory manufactures two types of Solar Trackers to be used with the Normal Incidence Pyrheliometer and the Cavity Radiometer.
The Automatic Solar Tracker, Model SMT-3 is a 2 axis, azimuth/elevation device programmed to align direct beam instruments with the normal incidence of the sun from any position on the earth’s surface. Tracking is achieved using a computer program which calculates the solar position for the time and location and transmits pulses to the drives, which then operate the 2 stepping motors. The stepping motors move the elevation and azimuth axes to the correct position. After initial installation, the tracker will continue to track the sun and reset during darkness. Only periodic resetting of the system clock is required.
The Models ST-1 and ST-3, "green tracker" are electrically driven using a clock-based motor which makes one revolution every 24 hours. The ST-1 is designed for use with a single instrument while the ST-3 accommodates up to three. The ST-3 also incorporates worm and gear fine adjustments for declination and equation of time.
HF ABSOLUTE CAVITY RADIOMETER 腔体式绝对辐射计
Model HF, AHF
The self-calibrating Absolute Cavity Pyrheliometer, Model HF, has been a reference standard level device for many years. The sensor consists of a balanced cavity receiver pair attached to a circular wire-wound and plated thermopile. The blackened cavity receivers are fitted with heater windings which allow for absolute operation using the electrical substitution method, which relates radiant power to electrical power in SI units. The forward cavity views the direct beam through a precision aperture. The precision aperture area is nominally 50 mm2 and is measured for each unit. The rear receiver views an ambient temperature blackbody. The HF radiometer element with baffle tube and blackbody are fitted into an outer tube which acts as the enclosure of the instrument. The Model AHF has an automatic shutter attached to the outer tube.
The operation of the cavity radiometer, and the measurement of the required parameters is performed using an appropriate control box. The control functions include setting of the calibration heater power level, activation of the calibration heater, selection of the signals to be measured and control of the meter measurement functions and ranges. The measured parameters include the thermopile signal, the heater voltage and the heater current which is measured as the voltage drop across a 10 Ohms precision resistor. The instrument temperature may also be measured using an internally mounted thermistor. The meter resolution of 100 nV allows for a thermopile signal equivalent in radiation of approximately 0.1 Wm-2.
Control boxes for manual or manual/automatic are available. The control box can operate either one radiometer in the measurement mode or two radiometers in the comparison mode. Automatic operation allows for computer control of shuttering, calibration heating and measurement functions. Calculation operations and data storage are also possible under computer control. Programs for independent, automatic measurement and cavity radiometer comparison are supplied with automatic units.
Although these are absolute devices, the radiometers are compared with the EPLAB reference cavity radiometers which have participated in the International Pyrheliometric Comparison (IPC) and other intercomparisons and are directly traceable to the World Radiation Reference (WRR).
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