Wind Speed; Wind Direction; Wind Speed Multiplier - Campbell 05103 Product Manual

7.4.1 Wind Speed

7.4.2 Wind Direction

Wind speed is measured by using the PulseCount() instruction. Syntax of the
the PulseCount() instruction is:
PulseCount(Dest, Reps, PChan, PConfig, POption, Mult, Offset)
Set the PConfig parameter to Low Level AC and the POption parameter to
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.
TABLE 7-2. Wind Speed Multiplier
Model
05103, 05103-45, or 05106
05108 or 05108-45
05305
Set the offset to zero since the helicoid propeller calibration passes through
zero (Gill, 1973; Baynton, 1976).
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) data logger uses the ExDelSE() instruction to measure wind
direction. All other CRBasic data loggers 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
band. To overcome this problem, all program examples use a delay of 20 ms
(20,000 μs) and set any negative wind direction values to 0.0: If WindDir < 0,
then WindDir = 0.0.
The excitation voltage, range codes, and multipliers for the different data
logger types are listed in TABLE 7-3. Appendix D, Wind Direction
Measurement Theory
(p. D-1)
measurement instruction.
Miles/ Meters/
Hour Output Second Output
0.2192 0.0980
0.3726 0.1666
0.2290 0.1024
, has additional information on the BRHalf()
Wind Monitor Series
12