Campbell Scientific SP-LITE Solar Radiation Sensor - Manual (Page 14)

SP-LITE Silicon Pyranometer
10
5.4 Program Example 2, Total Solar Radiation
In Example 2 a daily total flux density is found. This total flux density is in MJ
m
-2 day -1 . Negative values are set to zero before they are added to the running
total.
5.4.1 Output Format Considerations
If the solar radiation is totalized in units of kJ m
-2
, there is a possibility of
overranging the output limits. The largest number that the datalogger can
output to final storage is 6999 in low resolution and 99999 in high resolution
(Instruction 78, Set Resolution).
Assume that the daily total flux density is desired in kJ m -2 . 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, record an average flux (see Example 1). 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 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.
Wiring for Example 2
Color Function Example CR10X
Program Channels
Used
White Radiation Signal S.E. Channel 1
Green Signal Reference AG
Clear Shield G