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3 Operation
As shipped from the factory, the WSO200 automatically provides apparent wind direction,
apparent wind speed, outside air temperature, relative humidity, and barometric pressure and
requires no user configuration. However, some of the WSO200 parameters are user
configurable as described below:
• Installation Offset – As shipped from the factory, the WSO200 will read 0° apparent wind
direction when the wind blows into the sensor directly from the direction of the post
nearest the black humidity sensor that protrudes from the bottom of the sensor. If the
WSO200 is mounted with this post facing directly towards the bow of the boat, no
adjustment is necessary; however, if the sensor is mounted in any other orientation, the
installation offset can be used to compensate the apparent wind direction reading such
that it will read 0° when the apparent wind is blowing directly into the bow of the vessel.
• Wind Speed Damping Period – As shipped from the factory, the WSO200 uses a damping
period of 1.5 seconds to filter short-term variations in wind speed and direction and
provide a more stable, usable output. This damping period can be changed by the user
to increase or decrease the amount of filtering.
• Periodic Rate of Transmission – As shipped from the factory, the WSO200 transmits
PGNs at a periodic rate. Alternatively, a PGN can be disabled by programming its periodic
rate to zero.
Users with direct access to the NMEA 2000
through the NMEA 2000
®
2000
messages used to configure these parameters.
3.1 Ultrasonic Wind Speed Sensing
The wind speed measurement portion of the WSO200 consists of three sets of ultrasonic
transducers spaced equally around a horizontally-aligned circle.
The wind speed is measured by measuring the time of flight of an ultrasonic sound pulse
generated by one set of sensors and received by the other two sets of sensors. Each of the three
sets of sensors takes a turn at being the transmitter, which the remaining two sensors receive
the pulse. Wind blowing in the direction of flight of a pulse increases the speed of the pulse by
the amount of the wind speed. Measuring the time of flight in both directions between a given
pair of transducers allows the speed of sound to be cancelled out of the calculation, making the
wind speed computation independent of air temperature and relative humidity.
The ultrasonic transducers are robust, yet sensitive instruments. The transducers themselves
must be kept free of any coating, such as paint. The WSO200 unit itself, especially the area
between the transducers, must be kept clean and free of debris for maximum wind speed and
direction accuracy.
Revision 1.0
®
®
interface. Please refer to Appendix A for a description of the NMEA
interface may configure these parameters directly
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