Campbell Scientific LI200X-L LI-COR Silicon Pyranometer - Manual (Page 13)

LI200X Pyranometer
13: Real Time (P77)
1: 1220
Year,Day,Hour/Minute (midnight = 2400)
14: Resolution (P78)
1: 1
High Resolution
15: Totalize (P72)
1: 1
Reps
2: 4 Loc [ SlrMJ ]
16: Resolution (P78)
1: 0
Low Resolution
4.2 Total Solar Radiation
If the solar radiation is totalized in units of kJ m -2 , there is a possibility of
overranging the output limits. For CRBasic dataloggers, you can avoid this by
using the IEEE4 or long data format. The largest number that an Edlog
datalogger can output to final storage is 6999 in low resolution and 99999 in
high resolution.
For Edlog dataloggers, if you assume that the daily total flux density is desired
in kJ m
-2 and assume an irradiance of 0.5 kW m -2 , the maximum low resolution
output limit will be exceeded in just under four hours. This value was found
by taking the maximum flux density the datalogger can record in low
resolution and dividing by the total hourly flux density.
( )( ) 3 9
6999
0 5 3600
2
2 1 1
.
.
hr
kJ m
kJ m s s hr
=
−
− − −
(1)
To circumvent this limitation for Edlog dataloggers, record an average flux
(see Example 2). Then, during post processing, multiply the average flux by
the number of seconds in the output interval to arrive at a output interval flux
density. Sum the output interval totals over a day to find a daily total flux
density.
Another alternative for Edlog dataloggers is to record total flux using the high
resolution format (Instruction 78, see Datalogger manuals for details). The
disadvantage of the high resolution format is that it requires four bytes of
memory per data point, consuming twice as much memory as low resolution.
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.
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