1 output format considerations – Campbell Scientific CM3 Kipp and Zonen Pyranometer User Manual
Page 12
CM3 Pyranometer
8
5.2.1 Output Format Considerations
If the solar radiation is totalized in units of kJ m
-2
, there is a possibility of
over-ranging 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
kJm
kJm s
shr
=
−
−
−
−
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 an 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 manual 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. (Given the larger amount
of memory in today’s dataloggers, this may not matter.)
Example 2
;{CR10X}
;
*Table 1 Program
01: 10
Execution Interval (seconds)
1: Volt (Diff) (P2)
1:
1
Reps
2:
24
250 mV 60 Hz Rejection Range
3:
1
DIFF Channel
4:
1
Loc [ MJ_m2____ ]
5:
0.45725
Mult ;multiplier = [10s / (21870 mV / MJ/m2)]
Step 1 of 2
6:
0.0
Offset
2: Z=X*F (P37)
1:
1
X Loc [ MJ_m2____ ]
2:
0.001
F
Step 2 of 2
3:
1
Z Loc [ MJ_m2____ ]
;Set negative values to zero.
;
3: If (X<=>F) (P89)
1:
1
X Loc [ MJ_m2____ ]
2:
4
<
3:
0
F
4:
30
Then Do