CNR4 Net Radiometer
15
acquisition needs are more complex, the files that
Short Cut
creates are a great
source for programming code to start a new program or add to an existing
custom program.
Short Cut
cannot edit programs after they are imported and edited
in CRBasic Editor.
A
Short Cut
tutorial is available in Section
(p. 1)
. If you wish to
import
Short Cut
code into CRBasic Editor to create or add to a customized
program, follow the procedure in Appendix
(p. A-1)
. Programming basics for CRBasic data loggers are
provided below. Complete downloadable program examples are available at:
/downloads/cnr4-thermistor-example-program
/downloads/cnr4-pt100-example-program
/downloads/cnr4-cnf4-example-program
The CNR4 outputs four voltages that are measured with the
VoltDiff()
or
VoltSE()
CRBasic instructions. The voltage outputs typically range from 0 to
15 mV for the pyranometers, and
±
5 mV for the pyrgeometers.
7.4.1 Sensor Sensitivity
The CNR4 comes with four different sensor sensitivity values for four separate
probes. The CNR4 sensor comes with two copies of its ‘Certificate of
Calibration’ by the manufacturer. They show the sensor serial number and
sensitivity values for four individual probes: one copy for pyranometers, and
another copy for pyrgeometers. The serial number and sensitivity values are
also shown on a label affixed to the bottom of the sensor. If you choose to
attach the CNF4 heater/ventilator unit to the CNR4, the label showing the
serial number and sensitivity values will be covered. After attaching the CNF4
heater/ventilator, affix the extra label to the bottom of the CNF4 in a visible
location. The extra label containing the serial number and sensitivity values is
supplied with the purchase of the CNR4. Please refer to Appendix
(p. C-1)
, for more details.
The sensor sensitivity is in
µ
V/(W/m
2
). This needs to be converted into
(W/m
2
)/mV to be used as a multiplier parameter inside the data logger
program. To convert the units, divide the sensor sensitivity value into 1000.
For example, if the sensitivity is 7.30
µ
V/(W/m
2
), the multiplier is 1000/7.3 =
136.99 (W/m
2
)/mV.
7.4.2 Internal Temperature Sensors Programming
The thermistor is typically used with Campbell Scientific data loggers. The
thermistor is measured using the
BrHalf()
CRBasic instruction. The value
provided by the half bridge instruction needs to be converted to resistance and
then converted to temperature.
Use the following expression in the program to convert to resistance:
Rs = Rf*(Vx/(1-Vx))
NOTE
