Wind Direction Measurement Theory; D-1. 05103 Potentiometer In A Half Bridge Circuit - Campbell 05103 User Manual

Appendix D. Wind Direction
Measurement Theory
D.1 BRHalf Instruction
It is not necessary to understand the concepts in this section for the general
operation of the 05103 with Campbell Scientific's datalogger.
Figure D-1. 05103 potentiometer in a half bridge circuit
The BRHalf instruction outputs a precise excitation voltage (V
voltage between the wiper and ground (V
ground, R , and V varies with wind direction. The measurement result is the ratio
s s
of the measured voltage to the excitation voltage (V
the resistance as shown below:

 
V V R R R
s x s t s
The maximum value that R
west side of north to the east side of north (at this point R
maximum value of 1.0 mV/mV at 355 degrees. The multiplier to convert V
degrees is 355 degrees / 1.0 V
V / V , the multiplier is the same for both the CR10(X) and CR3000, even though
s x
they use a different excitation voltage. See Section 13.5 in the datalogger manual
from more information on the bridge measurements.
). The resistance between the wiper and
s

will reach is R , just before it crosses over from the
s f
/V = 355. Since the datalogger outputs the ratio
s x
), and measures the
x
/V ). This ratio is related to
s x
= 0). V / V reaches its
t s x
/V
s
to
x
D-1