Nortek Vectrino, User Manual

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Vectrino 15
Chapter 4
Functional Description
This section briefly describes some of the underlying principles that control
the operation and application of the Vectrino velocimeter.
The Vectrino has two modes of operation:
• Command mode.
In command mode the Vectrino is ready to accept
your instructions.
• Data Acquisition Mode. The Vectrino enters data acquisition mode
when you click any of the Start commands (e.g. Start Data Collection )
in the Vectrino software. The Vectrino collects data without interruption.
Doppler Theory
Sound does not reflect from
water, but from particles
suspended in the water. These
particles are typically
suspended sediment or seeding
particles, and move with the
same average speed as the
water. The velocity that is
measured is consequently the
velocity of the water. The Vectrino uses the Doppler effect to measure current velocity. The
Doppler effect is the change in pitch that is heard when either the source of
a sound or the listener is in motion. When you hear a vehicle with a siren,
the pitch is higher when the vehicle is heading towards you, and lower
when it is going away. The change in pitch tells you how fast the vehicle is
moving.
The Vectrino transmits short pairs of sound pulses, listens to their echoes,
and, ultimately, measures the change in pitch or frequency of the returned
sound.