Wind Direction; Wind Speed Multiplier - Campbell 05103 Instruction Manual

The expression for wind speed (U) is:
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).
Model
05103, 05103-45, or 05106
05305

7.4.2 Wind Direction

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 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. Edlog
dataloggers (CR510, CR10X, CR23X) use Edlog Instruction 4—Excite, Delay
(P4).
Some CRBasic measurement sequences cause the measurement of the wind
direction to return a negative wind direction (–30º) while in the dead band.
This can be overcome by using a delay of 40 ms (40,000µs) or by setting
negative wind direction values to 0.0: If WindDir < 0, then WindDir = 0.0.
The excitation voltage, range codes, and multipliers for the different datalogger
types are listed in TABLE 7-3. Appendix B has additional information on the
P4 and BRHalf() measurement instructions.
05103, 05103-45, 05106, and 05305 R.M. Young Wind Monitors
U = Mx + B
where
M = multiplier
x = number of pulses per second (Hertz)
B = offset
TABLE 7-2. Wind Speed Multiplier
Miles/
Hour Output
0.2192
0.2290
Meters/
Second Output
0.0980
0.1024
11