Campbell Scientific Q7_1-L REBS Net Radiometer - Manual (Page 3)

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Q-7.1 NET RADIOMETER
The Q-7.1 is a high-output thermopile sensor which measures the algebraic sum of incoming and
outgoing all-wave radiation (i.e. short-wave and long-wave components). Incoming radiation consists of
direct (beam) and diffuse solar radiation plus long-wave irradiance from the sky. Outgoing radiation
consists of reflected solar radiation plus the terrestrial long-wave component.
1. SPECIFICATIONS
•
60-junction thermopile with low electrical
resistance (4 ohms nominal) to reduce
susceptibility to noise
•
Nominal calibration factors 9.6 W m -2 mV -1
(for positive values), 11.9 W m -2 mV- 1 (for
negative values)
•
Spectral response 0.25 to 60 µm
•
Uncorrected wind effect: up to 6%
reduction @ 7 m s
-1 for positive fluxes, up
to 1% reduction @ 7 m s -1 for negative
fluxes.
•
Time constant: Approximately 30 seconds
•
Top and bottom surfaces painted black and
protected from convective cooling by
hemispherical heavy-duty polyethylene
windshields (0.25 mm thick)
•
Windshields do not require pressurization
•
O-ring seals for easy windshield
replacement
•
Desiccant contained in support arm;
volume of desiccant tube 45 cm
3
; breather
port on the end of the support arm.
•
No power required
•
Size of sensing head 57 x 72 x 177 mm;
support arm 20 mm diameter, 750 mm long
2. INSTALLATION
Attach the square mounting plate to a vertical or
horizontal pipe or rod that is less than 38 mm
(1.5 inches) in diameter with the two larger U-
bolts. Attach the radiometer support arm to the
mounting plate with the two smaller U-bolts.
The radiometer support arm does not need to be
level. Fasten the cable to the pipe or rod with
tape or plastic ties to prevent strain on the wires
and damage to the instrument.
CAUTION: Ensure that the cable is tied to
the support arm close to the ball joint. If
the wires are allowed to flex where they
emerge from the sensor head they will
break. Sensors are shipped with an
appropriate cable tie already installed.
In the northern hemisphere install the
radiometer so that the sensor head is pointing
south. Likewise, in the southern hemisphere
point the sensor head to the north.
2.1 LEVELING
The Q-7.1 must be level. The bubble level is
accurate to ±1° and the bubble should be within
the bulls-eye. An error of 5° in leveling may
cause a cosine response error of 6% under
normal conditions; much greater errors are
possible under other conditions (e.g. sunrise,
sunset and winter use with low sun angles).
To level the Q-7.1, use a 5/8" wrench on the
hexagonal coupling nut on the instrument stem
to bend the ball joint between the support arm
and the instrument. If the instrument does not
stay in position, tighten the large hexagonal nut
on the support arm slightly with a 15/16"
wrench.
CAUTION: Do not attempt to bend the ball
joint by holding the instrument head alone,
as this may break the stem.