FURUNO DS-50 Doppler Speed Log – DS-500 Display and System Parts

The FURUNO DS-50 is a marine Doppler speed log designed to measure and display a vessel’s fore-aft and port-starboard speed. It can also present distance travelled and keel-clearance information received through the system’s processor and underwater transducer.

The photographed component is the FURUNO DS-500 Main Display Unit, which forms the bridge display of the complete DS-50 system. Its large LED indicators provide clear speed and distance information for navigation and manoeuvring.

What Is the FURUNO DS-50?

The DS-50 uses the Doppler effect and a 440 kHz, three-beam ultrasonic transducer to calculate vessel movement. Its three-beam arrangement reduces the influence of vessel pitch and roll while allowing both longitudinal and transverse speed measurement.

The system can operate in:

• Ground-tracking mode: Measures speed relative to the seabed
• Water-tracking mode: Measures speed relative to the surrounding water
• Auto mode: Automatically selects an appropriate tracking mode
• Distance mode: Displays accumulated distance travelled
• Keel-clearance mode: Displays the measured distance beneath the keel

Technical figures are available in the FURUNO DS-50 Operator’s Manual.

Main Specifications

Manufacturer: Furuno Electric Co., Ltd.
Model: DS-50
Main Display: DS-500
Product Type: Dual-axis Doppler Speed Log
Ultrasonic Frequency: 440 kHz
Number of Beams: Three
Fore-Aft Speed Range: –10.0 to +40.0 knots
Port-Starboard Range: –9.9 to +9.9 knots
Ground-Tracking Depth: Approximately 1–200 metres beneath the keel
Water-Tracking Depth: Approximately 3–25 metres below the hull
Distance Display: Up to 99,999.99 nautical miles
Speed Accuracy: ±1% or ±0.1 knot, whichever is greater
Data Interface: IEC 61162 and other analogue/digital outputs
Power Supply: 115/230 VAC

Actual performance depends on transducer condition, installation, water depth, sea conditions and correct calibration.

Main Features

• Fore-aft and transverse speed indication
• Ground-tracking and water-tracking modes
• Distance-run calculation
• Keel-clearance indication
• Clear LED display suitable for bridge use
• Selectable knot and metre-per-second indication
• Adjustable display illumination
• Audible and visual alarm indication
• Outputs for external navigation equipment
• Optional remote speed and distance indicators

FURUNO DS-50 System Components

A complete DS-50 installation may include:

• DS-500: Main display unit
• DS-510: Processor unit with built-in transceiver
• DS-511: Processor unit for separated-transceiver installation
• DS-520: Separate transceiver unit
• DS-530: Three-beam underwater transducer
• DS-531: Transducer tank
• DS-532: Optional gate-valve arrangement
• DS-501: Remote-control box
• DS-350/DS-351: Optional digital indicators
• DS-370: Distribution box
• DS-381/DS-382: Analogue speed indicators
• DS-389: Range-switch box
• DS-730: Distance indicator

The exact equipment combination depends on whether the vessel uses a DS-510 processor with an integrated transceiver or a DS-511 processor with a separate DS-520 transceiver. Installation details can be checked in the DS-50 Installation Manual.

How the DS-50 Works

The hull-mounted DS-530 transducer sends ultrasonic signals toward the seabed or through the surrounding water. Reflected signals return with a frequency shift created by the vessel’s movement.

The processor calculates this Doppler shift and sends speed, distance and keel-clearance data to the DS-500 display and other connected bridge equipment.

Typical Marine Applications

• Merchant ships and container vessels
• Tankers and bulk carriers
• Offshore and support vessels
• Research and survey ships
• Bridge navigation systems
• Manoeuvring and berthing support
• Speed input for radar, ARPA, ECDIS and other compatible equipment
• Replacement of an existing DS-50 display or system component

Common Problems

No Speed Indication

Check the DS-530 transducer, processor power, transceiver, cabling, terminal connections and selected tracking mode.

Unstable or Incorrect Speed

Possible causes include transducer contamination, bubbles beneath the hull, shallow-water effects, rough seas, incorrect calibration or electrical interference.

Ground Tracking Is Lost

The seabed may be deeper than the working range, too soft or unsuitable for a strong acoustic reflection. The system may switch to water tracking when available.

No Keel-Clearance Reading

Check water depth, transducer condition, range settings and whether the system is receiving a usable bottom echo.

LED or Dimmer Problem

Inspect the DS-500 power supply, control panel, display PCB, illumination circuit and internal connectors.

Distance Does Not Accumulate Correctly

Verify the speed input, distance settings, pulse output, calibration and selected tracking mode.

Maintenance Recommendations

• Keep the transducer face free from marine growth and heavy coating.
• Inspect the transducer tank, gate valve and cable seals for leakage.
• Compare indicated speed with another reliable navigation source.
• Check ground and water tracking during sea trials.
• Inspect processor ventilation and power connections.
• Protect electronic units from moisture and excessive heat.
• Record calibration values before replacing a PCB or processor.
• Use qualified marine technicians for transducer and gate-valve work.

Why the FURUNO DS-50 Is Still Used

Although the DS-50 is a legacy system, many vessels continue using it because of its durable construction, clear LED presentation and ability to provide both longitudinal and transverse speed.

Maintaining an existing DS-50 can also be more economical than immediately replacing its processor, transducer, cabling and bridge indicators. However, modernization with newer Furuno equipment must be assessed as a complete system project rather than assuming direct plug-in compatibility. Furuno’s present speed-log range can be viewed on the official Furuno Speed Log page.

Frequently Asked Questions

Is the photographed unit a complete DS-50 system?
No. It is the DS-500 main display. A complete system also requires a compatible processor, transducer and associated installation equipment.

Can the DS-50 show sideways speed?
Yes. It can indicate port-starboard transverse speed as well as fore-aft speed.

Does it measure speed over ground or through water?
It supports ground tracking and water tracking within their respective operating-depth ranges.

Can a DS-500 display be replaced without calibration?
The replacement should be tested with the existing processor and checked against the master calibration settings before normal navigation.

What details are needed for a quotation?
Send photographs and nameplates of the display, processor, transceiver and transducer. Mention the required part number, quantity, vessel voltage and delivery country.

Short Product Description

FURUNO DS-50 Doppler Speed Log with DS-500 bridge display for fore-aft speed, port-starboard speed, distance run and keel-clearance indication. Suitable for compatible DS-510 or DS-511 processor arrangements with DS-530 three-beam transducer. Complete systems, display units and related spare parts are available subject to stock and technical confirmation.

Manuals and Technical Resources

• FURUNO DS-50 Operator’s Manual
• FURUNO DS-50 Installation Manual
• Archived FURUNO DS-50 Product Brochure
• Official FURUNO Speed Log Products

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