Campbell Scientific LI200X-LC Pyranometer for MetData1 - Manual (Page 8)

LI200X-LC PYRANOMETER FOR METDATA1
6
5. MAINTENANCE
On a monthly basis the level of the pyranometer
should be checked. Any dust or debris on the
sensor head should be removed. The debris
can be removed with a blast of compressed air
or with a soft bristle, camel hair brush. Check
that the drain hole next to the surface of the
sensor is free of debris.
CAUTION: Handle the sensor carefully
when cleaning. Be careful not to scratch
the surface of the sensor.
Recalibrate the LI200X every two years. Obtain
an RMA number before returning the LI200X to
Campbell Scientific, Inc. for recalibration.
6. CALIBRATION
LI200X pyranometers output a current that is
proportional to the incoming solar radiation.
Each LI200X has a unique calibration factor. A
variable shunt resistor in the cable converts the
current to the voltage measured by the
datalogger. Campbell Scientific sets the shunt
resistor so that the pyranometer outputs 5 mV
kW
-1
m
2
.
The resistor value is found using Ohms law.
The resistance is found by dividing the desired
output voltage by the calibrated current output.
For example, a pyranometer with a calibration
of 92
µ
A kW
-1
m
2
, will have the resistor set to:
54.35
Ω = − −
5 0 092 1 2 1 2 mV kW m mA kW m . .