Campbell Scientific NR01 Net Radiometer - Manual (Page 14)

NR01 Four-Component Net Radiation Sensor
#Outputs listed for both of the pyrgeometers are not compensated for sensor
temperature. For example, to correct for sensor temperature when the sensor
temperature is 14 ºC, you should add 385 W/m
2 to the pyrgeometer signals.
The raw reading of the upward facing pyrgeometer will generally be close to
zero when the sensor temperature is close to the ground temperature. You
should expect small negative readings when the sensor is located above cooled
surfaces (e.g. water or transpiring vegetation) or small positive readings when
the surface is emitting heat (e.g. warm soil at night).
* At night, dew deposition may affect the downward facing pyrgeometer’s
output. In that case, the signal may drop to 0 W/m
2 , producing a maximum
error of +100 W/m 2 . Campbell Scientific recommends activating the heater to
avoid dew deposition.
** During the day, the window-heating offset may affect the downward facing
pyrgeometer’s output. This can produce a maximum error of +15 W/m
2 .
***At night, the infrared offset may affect the downward facing pyranometer’s
output. The maximum error of this offset is -25 W/m
2 .
2.6 Heating
A heater is located in the connection body of the pyrgeometers to prevent dew
deposits on the sensor that may occur at night. Because of the heater’s current
drain, Campbell Scientific recommends using the heater only when necessary.
A relay can turn the heater on when the solar radiation is less than 20 W/m
2 .
See Section 4.3.1.
2.7 Data Quality Assurance
To assure quality data, look for unrealistic values when analyzing:
• Trends in SW
in
absolute signal,
• SW albedo
• Correlation of SW
in
and LW
in
• SW night time signals
• Correlation of relation LW
out
and surface temperature
3. Specifications of NR01
The NR01 is a four-component net-radiometer consisting of two pyranometers
of type SR01, two pyrgeometers of type IR01, a heater, and a Pt100
temperature sensor.
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