Measurement Programming Examples; Single-Ended Voltage - Li200S Silicon Pyranometer; Wiring Diagram For Li200S - Campbell Measurement and Control Module CR10 Operator's Manual

SECTION 7. MEASUREMENT PROGRAMMING EXAMPLES
This section gives some examples of Input Programming for common sensors used with the CR10.
These examples detail only the connections, Input, Program Control, and Processing Instructions
necessary to perform measurements and store the data in engineering units in Input Storage. Output
Processing Instructions are omitted (see Section 8 for some processing and program control examples).
It is left to the user to program the necessary instructions to obtain the final data in the form desired. No
output to final storage will take place without additional programming.
The examples given in this section would likely be only fragments of larger programs. In general, the
examples are written with the measurements made by the lowest numbered channels, the instructions
at the beginning of the program table, and low number Input Storage Locations used to store the data.
It is unlikely that an application and CR10 configuration exactly duplicates that assumed in an example.
These examples are not meant to be used verbatim; sensor calibration, input channels, and input
locations must be adjusted for the actual circumstances. Unless otherwise noted, all excitation
channels are switched analog output.
7.1 SINGLE-ENDED VOLTAGE - LI200S
SILICON PYRANOMETER
The silicon pyranometer outputs a current
which is dependent upon the solar radiation
incident upon the sensor. The current is
measured as the voltage drop across a fixed
resistor. The Campbell Scientific LI200S uses
a 100 ohm resistor. The calibration supplied by
LI-COR, the manufacturers of the pyranometer,
is given in µA/kW/m
values to volts multiply the µA calibration by the
resistance of the fixed resistor.
The calibration of the pyranometer used in this
example is 76.9 µA/kW/m
multiplied by 100 ohms equals 7.69mV/kW/m
The multiplier used to convert the voltage
2
reading to kW/m
2
0.13004 kW/m /mV.
Most LI-COR calibrations run between 60 and 90
2
µA/kW/m , which correspond to calibrations of
6.0 to 9.0mV/kW/m
atmosphere, the flux density through a surface
normal to the solar beam is 1.36kW/m
2
. To convert calibration
2
, which when
2
is 1/7.69mV/kW/m =
2
. Above the earth's
2
; radiation
FIGURE 7.1-1. Wiring Diagram for LI200S
at the surface of the earth will be less than this.
Thus, the 25mV scale provides an adequate
range (9.0mV/kW/m
CONNECTIONS
The pyranometer output can be measured with
a single-ended voltage measurement on
channel 5. There are twice as many single-
ended channels as differential channels and
they are numbered accordingly: Single-ended
channel 5 is the high side of differential channel
3 (3H); the low side (3L) is single-ended channel
6.
2
.
01: P1
01: 1
02: 23
03: 5
04: 1
05:
06: 0
2
x 1.36 kW/m
PROGRAM
Volt (SE)
Rep
25 mV 60 Hz rejection
Range
IN Chan
Loc [:RAD kW/m2]
.13004 Mult
Offset
2
< 25mV).
7-1