Campbell CNR2, Instruction Manual

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CNR2 Net Radiometer
4. Using the CNR2 in the Two Separate Components
Mode (2SCM)
The two pyranometers will measure the short-wave radiation (incoming from
the sky and reflected from the soil surface); the two pyrgeometers will measure
the long-wave radiation (incoming from the sky and reflected from the soil
surface). However, only one output for short-wave radiation (net short-wave)
and one output for long-wave radiation (net long-wave) will be given as a
result of the CNR2 measurements.
4.1 Measuring Solar Radiation with the Pyranometers
The upward-facing pyranometer measures incoming short-wave (global or
solar) radiation. The downward-facing pyranometer measures the reflected
short-wave (solar) radiation. When the final output of the net solar radiation is
made by the sensor, the reflected radiation is subtracted from the global
radiation.
To find the net short-wave radiation, divide the measured short-wave output
from the sensor by its sensitivity.
SW
SW
NETSW
S
U
E
=
(4.1)
Where, E
NETSW
is the net short-wave radiation in W m
-2
U
SW
is output voltage in µV
S
SW
is sensitivity in
2
m / W
V
μ
4.2 Measuring Far Infrared Radiation with the Pyrgeometers
The upward-facing pyrgeometer measures the far infrared radiation from the
sky. The downward-facing pyrgeometer measures the far infrared radiation
that is emitted by the ground.
The long-wave infrared signal output is the difference between incoming and
outgoing infrared radiation.
To find the net long-wave radiation, divide the measured long-wave output
from the sensor by its sensitivity.
2
LW
LW
NETLW
m / W
S
U
E
=
(4.2)
Where, E
NETLW
is the net long-wave radiation in W m
-2
U
LW
is output voltage in µV
S
LW
is sensitivity in
2
m / W
V
μ
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