HRP Instrument description

The High Resolution Profiler (HRP) is an oceanographic instrument designed to collect fine- and microstructure data during vertical profiles. A larger version of the schematic of the HRP's structure and component systems shown at the right is available here (figure by J.Cook ).

The HRP's operation is controlled by an onboard interface bus computer (IBC) that uses the original PC 8086 chip. In order to have the computer fit into a 6" diameter pressure case, the IBC was designed to fit on several small cards interfaced to the instrument backplane. This is also how the A/D sensors and integral CTD communicate with the computer. The software controlling the computers operation is written in C and assembler.

The HRP has two profiling modes: fine and micro, with the transition between them triggered by the CTD's pressure reaching user defined threshold values. Fine sensors (including the CTD) are sampled at 10 Hz, and microstructure sensors are sampled at 200 Hz, with fine sampling continuing throughout the period of micro sampling. Up to 16 sensors may be added to the HRP to complement the basic CTD measurements. The profiler is designed for versatility, so its configuration is determined by whichever suite of sensors is connected to the available channels.

The sensor configuration we normally use is shown below :

        fine sensors-                                A/D channel
                pressure
                temperature 
                conductivity
                accelerometer top X                       0
                accelerometer top Y                       1
                accelerometer bottom X                    2
                accelerometer bottom Y                    3
                acoustic current meter X velocity          4
                acoustic current meter Y velocity          5
                X magnetometer                             6
                Y magnetometer                             7
                A/D ground                                14
                
        micro sensors-                                  channel-
                differential conductivity                 10
                differential temperature                  11
                shear X                                   12
                shear Y                                   13
The sensors and their positions on the nose of the instrument are shown in the schematic below:
schematic of HRP sensors

To minimize ship induced noise in the measurements, the HRP profiles without attachment to the ship. It is deployed, falls freely while collecting data, releases its weights and ascends to the ocean surface where it can be recovered. Once on deck, the data is downloaded from instrument memory to a shipboard computer where analysis and archival occurs. At a nominal descent rate of 0.6 meters/second, a 1000 meter dive typically takes thirty minutes, during which time one half megabyte of fine data and two megabytes of micro data will be acquired and stored, given the above configuration.

For additional information on the development of the HRP, see the these papers:

  • Schmitt, R. W., J. M. Toole, R. L. Koehler, E. C. Mellinger, and K.W.Doherty, 1988. The development of a fine- and microstructure profiler. Journal of Atmospheric and Oceanic Technology, 5(4), 484-500.
  • Montgomery, E. T., 1991. High Resolution Profiler (HRP) user's guide and software modifications documentation. Woods Hole Oceanographic Institution Technical Report 91-01,  32 pp.
  • Montgomery, E. T. and R. W. Schmitt, 1997.  Acoustic Altimeter control of a free vehicle for near-bottom turbulence measurements.  Deep-Sea Research, 44, 6, 1077-1084.
  • Schmitt, R. W., E. T. Montgomery, and J. M. Toole,  1995.  A free vehicle explores deep-sea mixing.  Oceanus, 38 (1), 21-25.

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