Campbell Scientific LI200X-LC Pyranometer for MetData1 - Manual (Page 6)

LI200X-LC PYRANOMETER FOR METDATA1
4
07: Average (P71)
1:
1 Reps
2: 1* Loc [ W_m2 ]
-Input Locations-
1 W_m2
* Proper entries will vary with program.
*** See Table 4-1 for alternative multipliers.
4.2 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.
4.2.1 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.