Using a Velocimeter 23
© 2018 Nortek AS
2.1 Vector
2.1.1 Technical description
For technical specifications, check out the product on our website.
Probe with Transducers
The probe is mounted either on a cable or a fixed stem connected to the main housing through the
probe endbell. The probe consists of three receiver transducers, each mounted inside a receiver arm,
and a transmit transducer at the center. When an instrument uses separate transmit- and receive
transducers, it is called a bistatic sensor.
The center transducer transmit the sound waves, and the three receivers listen and measure the
Doppler shifted return signal.
Pressure Sensor
The Pressure sensor is located inside the probe endbell. The pressure sensor provides instrument
depth data, and can also be used for wave measurements.
The pressure sensor is not calibrated to, or corrected by the atmospheric pressure. This means that
the pressure sensor reading will follow the atmospheric pressure. Therefore, a pressure offset should
be run before using the instrument, and this can be done using the Vector software; click Menu: 'On-
line' - 'Set Pressure Offset...'.
The pressure sensor offset should be run right before the instrument id deployed. The pressure offset
corrects for local atmospheric pressure, so by definition we want the pressure sensor to read zero in
the air. If there were not large changes in atmospheric pressure relative to the current pressure
offset, or the pressure sensor sensitivity was less than any atmospheric pressure changes, then the
pressure sensor will read zero in the air.
The pressure data is collected at the same rate as velocity, which is set by the user in the
Deployment Planning under Sampling Rate. That means that it can sample at up to 64 Hz.
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