Wind direction measurement theory
It is not necessary to understand the concepts in this section for the general operation of the
05103 potentiometer in a half bridge circuit
The BRHalf CRBasic instruction outputs a precise excitation voltage (Vx) and measures the voltage between the wiper and ground (Vs). The resistance between the wiper and ground (Rs) and Vs vary with wind direction. The measurement result is the ratio of the measured voltage to the excitation voltage (Vs/Vx). This ratio is related to the resistance, as shown in this equation:
The maximum value that Rs will reach is Rf, just before it crosses over from the west side of north to the east side of north (at this point Rt = 0). Vs / Vx reaches its maximum value of 1.0 mV/mV at 355 degrees. The multiplier to convert Vs/Vx to degrees is 355 degrees / 1.0 Vs/Vx = 355. Refer to the data logger manual for more information on the bridge measurements.