Campbell Scientific 05103, 05103-45, 05106, and 05305 R. M. Young Wind Monitors - Manual (Page 28)

Appendix B. Wind Direction Measurement Theory
B-2
B.2 EX-DEL-SE (P4) Instruction
Instruction 4 outputs a precise excitation voltage (V
x
) and measures the voltage
between the wiper and analog ground, V
s
. The resistance between the wiper
and analog ground, R
s
, and V
s
varies with wind direction. Instruction 4 outputs
the measured voltage, V
s
. This measured voltage is related to resistance as
shown below:
( )
s t s x s
R R R V V + ⋅ =
The maximum value that R
s
will reach is R
f
just before it crosses over from the
west side of north to the east side of north (at this point R
t
= 0). V
s
reaches its
maximum value of V
x
. This maximum voltage equals 2500 mV for an
excitation voltage of 2500 mV recommended for the CR10(X) and 5000 mV
for an excitation voltage of 5000 mV recommended for the CR23X at 355
degrees. The multiplier to convert V
s
to degrees is 355 degrees / 2500 mV =
0.142 for the CR10X, or, 355 degrees / 5000 mV = 0.071 for the CR23X. See
Section 13.5 in the datalogger manual from more information on the bridge
measurements