Using a Velocimeter 23© 2018 Nortek AS2.1 Vector2.1.1 Technical descriptionFor technical specifications, check out the product on our website.Probe with TransducersThe probe is mounted either on a cable or a fixed stem connected to the main housing through theprobe 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 receivetransducers, it is called a bistatic sensor.The center transducer transmit the sound waves, and the three receivers listen and measure theDoppler shifted return signal.Pressure SensorThe Pressure sensor is located inside the probe endbell. The pressure sensor provides instrumentdepth data, and can also be used for wave measurements.The pressure sensor is not calibrated to, or corrected by the atmospheric pressure. This means thatthe pressure sensor reading will follow the atmospheric pressure. Therefore, a pressure offset shouldbe 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 offsetcorrects for local atmospheric pressure, so by definition we want the pressure sensor to read zero inthe air. If there were not large changes in atmospheric pressure relative to the current pressureoffset, or the pressure sensor sensitivity was less than any atmospheric pressure changes, then thepressure 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 theDeployment Planning under Sampling Rate. That means that it can sample at up to 64 Hz.
