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Instrumentation

BB150 System

150 khz Broadband Instrument

The first LADCP configuration used at WHOI in November, 1994 consisted of a single downward facing 150 khz Broadband ADCP. We no longer have any working BB150 instruments in our LADCP inventory. These have now been replaced with 150 kHz Workhorse instruments (described below). In near surface regions of high scatter, the BB150s had a range of up to 400 meters. This dropped significantly in the deep ocean where lack of scatterers can reduce range to near zero. Due to a lack of replacement parts, we will no longer be using BB150s.

Dual Workhorse System

Example Package with Dual Workhorse System

In 2000, a dual Workhorse LADCP system was developed at WHOI. The need for a new instrument configuration was driven by Teledyne RDI's decision to discontinue the Broadband line of ADCPs. The dual ADCP system consists of a pair of 300 khz Workhorse ADCPs mounted on a CTD rosette in an upward and downward facing configuration. Both instruments are powered by a single rechargeable battery pack. Each instrument provides about 125 meters of range under ideal scattering environments, The dual system doubles that range and also provides valid data from the upward facing ADCP when the CTD package is near the bottom.

Listed below are some requirements and suggestions if adding these components to your own CTD frame.

  • Note both ADCPs should have a clear view of open water.
  • Upward ADCP should be mounted towards outer edge of rosette perimeter yet still within the protection of the frame.
  • Downward ADCP should be as far from battery and CTD as possible to avoid possible compass contamination.
  • Diameter of brackets for ADCP's and battery case should be oversized by 1/4" to allow for 1/8" neoprene strips to be glued onto each bracket. The neoprene allows for a tighter fit when bolted and protects the paint.
  • Note gussets on battery brackets for additional strength if necessary.
  • An exact wooden replica of a Workhorse ADCP can be provided for bracket design and frame fitting.

Hybrid System

Hybrid Configuration

In 2004, we began using the hybrid LADCP configuration. This consists of a downward facing 150 khz ADCP and an upward facing 300 khz ADCP. This system combines the benefits of increased range from a BB150 instrument with the ability to collect data near the sea bottom from a dual Workhorse system. The only drawback from this confifuration has been the inability to use ping synchronization between the two instruments to minimize ping interference from one instrument to the other. However, by using different ping timing, the interference can be minimized.

This system is also powered from a single battery pack. Due to the increased power demands of the BB150 instrument, a new battery system was developed for this generation of LADCPs. We now use an oil-filled pack that does not require a pressure case. This provides an increase from 9 amp-hours to 12 amp-hours capacity for the LADCP instruments.