Campbell Scientific CS300 Silicon Pyranometer - Manual (Page 19)

CS300 Pyranometer
TABLE 7-2. Multipliers Required for Average Flux
and Total Flux Density in SI and English Units
UNITS MULTIPLIER PROCESS
W m -2 5.0 Average
MJ m -2 t • 0.000005 Total
kJ m -2 t • 0.005 Total
cal cm –2 min –1 0.005 • (1.434) Average
cal cm –2 t • 0.005 • (0.0239) Total
t = datalogger execution interval in seconds
Nearby AC power lines, electric pumps, or motors can be a source of electrical
noise. If the sensor or datalogger is located in an electrically noisy
environment, the measurement should be made with the 60 or 50 Hz rejection
integration option as shown in the example programs.
7.4.1 Total Solar Radiation
If 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. With the Edlog dataloggers the largest
number that the datalogger can output to final storage is 6999 in low resolution
(default), and 99999 in high resolution.
For Edlog dataloggers, if you assume that the daily total flux 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 the datalogger can record in low resolution and dividing by
the total hourly flux.
( )( )
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.
Then, during post processing, multiply the average flux by the number of
seconds in the output interval to arrive at an output interval flux. Sum the
output interval totals over a day to find a daily total flux.
Another alternative for Edlog dataloggers is to record total flux using the high
resolution format. Instruction 78 is used to switch to the high resolution. The
disadvantage of the high resolution format is that it takes more memory per
data point.
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