
CMP6-L, CMP10-L, CMP11-L, and CMP21-L Pyranometers
15
TABLE 7-4. CMP21 Single-Ended Connections to Campbell Scientific Dataloggers
CR9000(X),
CR5000, CR3000,
CR1000, CR800
7.3 Programming
This section is for users who write their own datalogger programs.
You do not need to read this section if using Short Cut Program
Generator, or connecting the pyranonmeter to a prewired
enclosure or CWS900 Wireless Sensor Interface. Our prewired
enclosures include a datalogger program. Refer to the Wireless
Sensor Manual for programming information if using a CMP6,
CMP10 or CMP11 with a CWS900.
7.3.1 Solar Radiation Measurement
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
7-5. Programming examples are given for both average and daily total solar
radiation.
The pyranometers output a low level voltage ranging from 0 to a maximum of
up to 20 mV, in natural light, depending on the calibration factor and radiation
level.
This voltage output is measured using either a differential voltage instruction
(VoltDiff() in CRBasic or Instruction 2 (P2) in Edlog) or a single-ended
voltage instruction (VoltSE() in CRBasic or Instruction 1 (P1) in Edlog).
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.
7.3.1.1 Input Range
The output voltage is usually between 5 and 20 mV per 1000 W•m
–2
. When
estimating the maximum likely value of sensor output a maximum value of
solar radiation of 1100 W•m
–2
can be used for field measurements on a
horizontal surface. Plane of array irradiances can exceed 1500 W•m
–2
.
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