Introduction
MetPak Base Station User Manual
©
Gill Instruments Ltd
Last Change
Page 2
22 April, 2013
1.1
Principle of Operation
1.1.1
Wind Speed and Direction Sensor
The MetPak Base Station can be used with Gill 2axis (WindSonic or
WindObserver) or 3 axis (WindMaster or WindMaster Pro) wind speed and
direction sensors. They are connected via the supplied RS422 10 Metre lead. The
sensors measure the times taken for an ultrasonic pulse of sound to travel from the
North transducer to the South transducer, and compares it with the time for a pulse
to travel from S to N transducer. Likewise times are compared between West and
East, and E and W transducer.
If, for example, a North wind is blowing, then the time taken for the pulse to travel
from N to S will be faster than from S to N, whereas the W to E, and E to W times
will be the same. The wind speed and direction can then be calculated from the
differences in the times of flight on each axis. This calculation is independent of
factors such as temperature.
Figure 1
U and V Compass points 2 Axis Instruments
Figure 2 Compass points and polarity of U, V and W on a 3 axis instrument.
