Young Aspirated Radiation Shield Model 43502 - Manual (Page 2)

Page 1
43502-90(C)
MODEL 43502-90
COMPACT ASPIRATED
RADIATION SHIELD
INTRODUCTION
Model 43502 Aspirated Radiation Shield provides accurate ambient
air temperature measurements in a unique low cost, small size, and
conservatively rated instrument. Radiation errors are less than 0.2°
C RMS with the shield exposed to solar radiation of 1000 W/m2. The
triple wall shield employs three concentric downward facing intake
tubes and a canopy shade to isolate the temperature sensor from direct
and indirect radiation. The temperature sensor mounts vertically in the
center of the intake tubes.
Model 41342 Temperature Probe and Model 41382 RH/Temperature
Probe fit directly in a mounting ring within the shield. The convenient
Model 41390 Junction Box, which is available separately, will accept
other RTD, thermocouple, or thermistor type sensors with sheath
diameters up to 10 mm (0.4 in) and 150 mm (6.0 in) in length. Other
types of sensors up to 20 mm diameter can also be accommodated in
the shield. Longer probes may be used with the optional Model 43476
Extender Tube.
The small shield size reduces the surface area exposed to incoming
radiation during the day, significantly reducing the amount of heat that
needs to be washed away from the intake tubes. Errors from outgoing
radiation at night are similarly reduced. A continuous duty brushless
DC blower pulls ambient air into the shield and across the temperature
sensor. Flow rate at the sensor is 5 to 11 m/s, depending upon sensor
size. Brush-less electronic commutation of the blower motor is achieved
using dependable solid-state circuitry. The blower is designed for
continuous duty of more than 80,000 hours (9 years) at 25° C (77° F).
The blower housing and shield assembly are made from white UV
stable plastic, which provides high reflectivity, low heat conduction, and
maximum weatherability. The mounting bracket with a plastic v-block
and stainless steel U-bolt will accommodate a vertical mounting post of
25 to 50 mm (1 to 2 in) diameter and allows easy height adjustment.
The Model 43502 is ideally suited for lapse rate measurements. With
identical shields and sensors at 2 m and 10 m levels, the temperature
difference (delta T) can be measured with a relative accuracy of 0.05° C
RMS under conditions of maximum solar radiation.
EXPOSURE
The ideal shield location is over dry, flat terrain with a grass surface.
Avoid locations near large buildings, paved areas, rooftops, tunnels,
or other structures, which may exhaust warm air or radiate heat. Give
careful consideration to the effects of lakes or ponds which can modify
air temperature dramatically, low areas that hold standing water after
rains, sheltered hollows, high vegetation, and steep slopes and valleys
which are subject to air drainage from remote locations.
As a general rule, locate the shield downwind at a distance at least four
times the height of any nearby obstructions and at least 30 m (100 ft)
from paved areas.
Mount the shield on a tower or other supporting structure on the side of
the prevailing wind or direction of primary interest. This will reduce the
chance for errors introduced by air warmed by the supporting structure
itself.
For more detailed information about siting refer to the Quality
Assurance Handbook for Air Pollution Measurement Systems, Volume
IV - Meteorological Measurements (U.S. Environmental Protection
Agency, Atmospheric Research and Exposure Assessment Laboratory,
Research Triangle Park, NC 27711).
SPECIFICATIONS:
Sensor Types: Accomodates temperature and humidity sensors up
to 24mm (0.9 in) diameter
Radiation Error
Ambient Temp: <0.2°C (0.4°F) RMS (@1000 W/m² intensity)
Delta T: <0.05°C (0.1°F) RMS with like shields equally
exposed
Aspriation Rate: 5 to 11 m/s (16-36 fps) depending on sensor size
Power Reqmt: 12-14 VDC@500 mA for blower
Operating -50° to +60° C. (-58° to +140° F.)
Temperature
Range
DIMENSIONS
Overall Height: 33 cm (13 in)
Overall Diameter: 20 cm (8 in)
Shield:
7 cm (2.7 in) dia. x 12 cm (4.7 in)
Blower Housing: 17 cm (6.7 in) dia. x 11 cm (4.3 in)
Mounting:
V-Block and U-Bolt for vertical post or tower member
25-50 mm (1.0-2.0 in) dia.