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Wind Monitor Series
7.4.1 Wind Speed
7.4.2 Wind Direction
12
import Short Cut code into CRBasic Editor to create or add to a customized
program, follow the procedure in Appendix A, Importing Short Cut Code Into
CRBasic Editor
. Programming basics for CRBasic dataloggers are
(p. A-1)
provided in the following sections. Complete program examples for select
CRBasic dataloggers can be found in Appendix B, Example Programs
Programming basics and programming examples for Edlog dataloggers are
provided at
www.campbellsci.com\old-manuals.
For CRBasic dataloggers, wind speed is measured using the PulseCount()
instruction. Syntax of the the PulseCount() instruction is:
PulseCount( Dest, Reps, PChan, PConfig, POption, Mult, Offset )
The PConfig parameter should be set to 1 (Low Level AC) and the POption
parameter should be set to 1 (Frequency).
The expression for wind speed (U) is:
U = Mx + B
where
M = multiplier
x = number of pulses per second (Hertz)
B = offset
TABLE
7-2
lists the multipliers to obtain miles/hour or meters/second when
the measurement instruction is configured to output Hz.
The helicoid propeller has a calibration that passes through zero, so the offset is
zero (Gill, 1973; Baynton, 1976).
TABLE 7-2. Wind Speed Multiplier
Model
05103, 05103-45, or 05106
05108 or 05108-45
05305
The wind vane is coupled to a 10 kΩ potentiometer, which has a 5 degree
electrical dead band between 355 and 360 degrees. A 1 MΩ resistor between
the signal and ground pulls the signal to 0 mV (0 degrees) when wind direction
is in the dead band (between 355 and 360 degrees).
The CR200(X) datalogger uses the ExDelSE() instruction to measure wind
direction. All other CRBasic dataloggers use the BRHalf() instruction.
Some CRBasic measurement sequences can cause the measurement of the
wind direction to return a negative wind direction (–30º) while in the dead
Miles/
Meters/
Hour Output
Second Output
0.2192
0.0980
0.3726
0.1666
0.2290
0.1024
.
(p. B-1)
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