Campbell CM3, Instruction Manual, Page: 10 / 16

CM3 Pyranometer
6
5. Example Programs
Solar radiation can be reported as an average flux density (W m
-2
) or daily total
flux density (MJ m
-2
). The appropriate multipliers are listed in Table 5-1.
Programming examples are given for both average and daily total solar
radiation.
The output from the CM3 varies from 10-35 x 10
-6
V / W m
-2
. Given a
maximum solar radiation of 1500 W m
-2
, the maximum sensor output voltage
will be 15 - 52.5 mV. Example:
(21.87 x 10
-6
V W
-1
m
2
)
∗
(1500 W m
-2
) = 0.03281 V or 32.81 mV
TABLE 5-1. Multipliers Required for Average Flux and
Total Flux Density in SI and English Units
UNITS MULTIPLIERS
W m
-2
1
10
3
C
∗

 

(average)
MJ m
-2
t
C
∗

 

10
9
(total)
kJ m
-2
t
C
∗

 

10
6
(total)
cal cm
-2
min
-1
1 4333
10
6
.
C
∗

 

(average)
cal cm
-2
t
C
∗
∗

 

0 02389
10
6
.
(total)
C=CM3 calibration: eg. 21.87x10
-6
V / W m
-2
t = datalogger execution interval in seconds
5.1 Average Solar Radiation
Example 1 shows the program instructions used by a CR10X to measure the
signal from the CM3. A sixty-minute average is calculated and stored in final
storage.