Several of our instruments have a central beam in addition to the slanted ones. While the slanted beams mainly are used to measure the three dimensional current flow pattern (see Principles of Operation - Currents for details), the central beam with a vertical orientation can have different areas of use, depending on the instrument.

AWAC

The AWAC instruments have three slanted beams for measuring currents and one vertical, central beam. The central beam is only used for Acoustic Surface Tracking (AST) enabling a direct measure of the distance to the surface. The AST is used to measure waves. For more information about the AST and wave measurements, please refer to Principles of Operation - Waves. Note that this means the fourth, vertical beam on the AWAC can not be used to measure velocities.

Signature

Note that all uses of the central transducer on a Signature instrument requires an additional license. 

The Signature 500 and Signature 1000 both have four slanted beams and an additional vertical central beam. This central beam can, similarly as for the AWAC, be used to measure the distance to the surface using AST. In addition, these instruments can use the vertical beam to do a direct measure of vertical velocity or it can be used as an echosounder.

The Signature 250 can be bought both with and without a fifth central transducer. The fifth beam, if presence, can be used for wave measurements.

The Signature 100 also comes both with and without a fifth central transducer. The fifth beam for the Signature 100 is an echosounder, and can only be used for this application.