Select a windy day to take the calibration readings in an unsheltered position. Another alternative is to get a reference wind speed from a traditional rotating cup anemometer. As most of us do not have access to a calibrated wind tunnel, we can use the local weather forecast to provide a reference for the actual wind speeds. The next step is to convert these readings into meaningful measurements of wind speed. So far, we have made an instrument that gives two voltages according to the wind strength and direction.
As a final operational test, blow some air into the anemometer with a cold hair dryer and make sure the two phase detectors give a change in output voltage. Check the output from the phase detectors to see if the mark space ratio is symmetrical, if not, the system can be adjusted by altering the reflector spacing or the sensor depth in the fibre board. Once there is a good signal from all three sensors, the phase lock loop can be reinstated. The reflector plate spacing can also be adjusted for the highest signal, about 10 mm is a good starting point. Now we need to measure the signal on the receiver transducers and fine tune the frequency for maximum output corresponding to the resonance frequency of the sensors. Adjust the variable resistor to make the output on pin 4 run at 40 kHz.
ANEMOMETER DIAGRAM SERIES
Temporarily wire two 10k resistors in series across the voltage supply and connect pin 9 of the phase lock loop IC to this half voltage point. The setup requires a basic oscilloscope to tune up the anemometer.
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