APPLICATION NOTE NO. 59
A Load-Bearing Underwater Cable for Hand-Hauled, Real-Time Profiling
Revised October 2012

Print version

Profiling in real time, from small boats not equipped with a winch, calls for hand hauling a CTD using a load-bearing data cable. Sea-Bird can supply cables up to 300 meters (985 feet) in length that provide a practical way to hand-haul SBE 19 / 19plus /19plus V2 SeaCAT Profilers or SBE 25 / 25plus Sealogger CTDs, and acquire CTD profile data in real time. In these cases the CTD is powered by its battery, and the cable allows two-way* RS-232 communications (3 conductors - transmit, receive, and common) and bears the weight of the CTD.

The cable is not intended for static working loads above 45 kg (100 lbs); working loads above 18 kg (40 lbs) may be difficult to handle without a winch. The minimum recommended cable bend radius is 10 cm (4 in.) (e.g., 20 cm sheave block nominal diameter). Use with loads exceeding 45 kg (100 lbs) or cable bend radius less than 10 cm (4 inches) will reduce the cable's useful life and void the warranty.

Drawings show the cable assembly and wiring details, and include tables of Sea-Bird part numbers for cables of specific lengths:

• Drawing No. 32284 -- Standard connector to the CTD and 9-pin connector to the computer
• Drawing No. 32643 -- Wet-pluggable connector to the CTD and 9-pin connector to the computer
• Drawing No. 32821 -- Standard connector to the CTD and 4-pin connector to a SeaCAT/Sealogger RS-232 & Navigation Interface Box (Interface Box PN 90488 or PN 90545)

If the length you need is not listed on the drawing, contact Sea-Bird with the drawing number and desired length (300 meter [985 feet] maximum).

* Notes:

• Communications from the CTD to a computer -- An SBE 19, 19plus, 19plus V2, 25, or 25plus reliably transmits data over 300 meters (985 feet) of cable to a computer. See the applicable CTD manual for baud rate and real-time output rate limitations.
• Communications from a computer to the CTD for instrument setup, data upload, etc. are dependent on the computer serial port hardware and software settings, but are usually reliable over cables up to 300 meters (985 feet) long at low baud rates. Some laptop computers may have inferior serial port hardware, limiting the cable length over which they can transmit. If a computer cannot transmit over a long cable, disconnect the CTD from the long cable and connect to the computer using the shorter I/O cable provided with the CTD.

1. Communicate with the CTD via the terminal program* to set up sampling parameters, initialize memory, etc. (see terminal program Help Files).
2. Configure Seasave for real-time acquisition and display (see Seasave Help files).
3. Start the CTD sampling via magnetic switch (or with computer command in the terminal program* per CTD manual instructions).
4. Deploy the CTD to begin profile.
5. Recover the CTD.
6. Stop the CTD sampling via magnetic switch (or with computer command in the terminal program*).
7. Communicate with the CTD via the terminal program* to upload data.

*Note:
Sea-Bird has several terminal programs for communicating with instruments --

• SBE 19, 19plus, and 25: use Seaterm terminal program
• SBE 19plus V2 and 25plus: use SeatermV2 terminal program

• Nominal O.D. 7 mm (0.270 in.)
• Twisted trio of 22 awg conductors
• Pressure-extruded polyurethane jacket, dull, non-slip finish
• Weight in air approximately 50 grams/meter (0.034 lbs/ft)
• Weight in water approximately 4 grams/meter (0.0027 lbs/ft)
• PMG-4FS connector with locking sleeve to CTD and DB-9 serial data connector to computer -- Drawing No. 32284
• MCIL-4FS wet-pluggable connector with locking sleeve to CTD and DB-9 serial data connector to computer -- Drawing No. 32643
• PMG-4FS connector with locking sleeve to CTD and MS3106A-14S-2P connector to SeaCAT/Sealogger RS-232 & Navigation Interface Box -- Drawing No. 32821
• Mechanical terminations are Chinese finger trap type, made from hollow-core, polypropylene rope with stainless thimbles
• Internal Kevlar braid with 180 kg (400 lb) breaking strength
• Maximum recommended working load 45 kg (100 lbs)
• Minimum recommended cable bend radius 10 cm (4 inches) (e.g., a 20-cm sheave block nominal diameter)

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