Yokogawa EML-500 Speed Log

Complete Marine Technical Guide for Navigation Professionals

Manufacturer

Yokogawa Denshikiki Co., Ltd.

Country of Origin

Japan

Product Type

Marine Electromagnetic Speed Log System

Marine Application

Ship Speed Measurement, Distance Recording, Navigation Data Distribution, ECDIS Integration, AIS Input, VDR Recording, Bridge Navigation Systems

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Product Introduction

The Yokogawa EML-500 Speed Log is a highly reliable marine speed and distance measuring system designed for commercial vessels operating worldwide. The system continuously measures vessel speed through water and calculates travelled distance, providing essential navigation data to bridge equipment and integrated navigation systems.

For decades, Yokogawa navigation products have been trusted aboard:

• Tankers
• Bulk Carriers
• Container Ships
• Offshore Support Vessels
• LNG Carriers
• Passenger Vessels
• Research Ships

The EML-500 became particularly popular because of its reliability, accuracy, and seamless integration with modern bridge systems.

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Main Equipment

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The image above shows the Yokogawa EML-500 Speed Log Master Unit available from SM MARINE SERVICE™.

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What Is a Marine Speed Log?

A marine speed log is an instrument used to determine:

• Ship Speed Through Water (STW)
• Distance Travelled
• Navigation Performance
• Voyage Data Recording Inputs

Unlike GPS speed, which measures speed over ground (SOG), the speed log provides direct water-referenced speed information, which remains essential for safe navigation and ship maneuvering.

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Yokogawa EML-500 System Components

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How the Yokogawa EML-500 Works

The EML-500 utilizes electromagnetic measurement technology.

Electromagnetic Principle

The system generates a magnetic field around the transducer.

As seawater passes through this magnetic field, a voltage is generated proportional to vessel speed.

The electronics process this signal and calculate:

• Ship Speed
• Distance Run
• Navigation Data Output

Continuous Monitoring

The system continuously updates:

• Speed Through Water
• Total Distance
• Voyage Distance
• Navigation Data Outputs

This information is distributed to navigation systems throughout the vessel.

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Typical Shipboard Installation

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Main Features

Accurate Speed Measurement

Provides reliable vessel speed information under varying sea conditions.

Distance Recording

Calculates total and voyage-specific distance travelled.

Navigation System Integration

Interfaces with:

• ECDIS
• AIS
• VDR
• Radar
• Autopilot
• Integrated Bridge Systems

Continuous Data Output

Real-time speed information is available for navigation decisions.

Rugged Marine Design

Built to withstand harsh shipboard environments.

Long Operational Life

Many EML-500 systems remain operational after decades of service.

Low Maintenance Requirements

Simple design reduces maintenance workload.

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Main Components

A complete Yokogawa EML-500 installation generally consists of:

Master Display Unit

Bridge-mounted operator interface.

Signal Processing Unit

Processes speed measurement signals.

Electromagnetic Transducer

Installed below the vessel hull.

Power Supply Unit

Provides stable operating voltage.

Interface Modules

Transmit data to connected systems.

Communication Outputs

Supports navigation equipment integration.

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Display & Control Units

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Marine Applications

The EML-500 is commonly used for:

Navigation Operations

Provides accurate speed information to navigation officers.

ECDIS Integration

Supports route monitoring and voyage planning.

AIS Data Input

Provides vessel speed information.

Voyage Data Recording

Records speed data for voyage analysis.

Fuel Efficiency Monitoring

Assists operators in optimizing vessel performance.

Harbor Maneuvering

Supports precise vessel handling.

Offshore Operations

Provides reliable speed references during offshore activities.

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Common Problems & Troubleshooting

No Speed Indication

Possible Causes:

• Transducer Failure
• Power Supply Fault
• Signal Cable Damage

Solutions:

• Verify Power Supply
• Inspect Transducer Connections
• Check Input Signals

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Unstable Speed Reading

Possible Causes:

• Marine Growth on Sensor
• Damaged Transducer
• Electrical Noise

Solutions:

• Clean Sensor Surface
• Verify Shielded Cabling
• Inspect Transducer Condition

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Incorrect Distance Calculation

Possible Causes:

• Calibration Error
• Processing Unit Fault
• Sensor Problems

Solutions:

• Verify Calibration Parameters
• Perform System Diagnostics

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Communication Failure

Possible Causes:

• Interface Card Problems
• Wiring Faults
• Port Configuration Errors

Solutions:

• Inspect Output Connections
• Verify Communication Settings

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Alarm Indications

Possible Causes:

• Sensor Failure
• Signal Loss
• Power Issues

Solutions:

• Review Alarm Codes
• Check Sensor Inputs
• Verify System Voltage

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Maintenance Tips

To maximize system reliability:

Monthly Checks

• Verify Display Accuracy
• Check Alarm Functions
• Inspect Wiring

Quarterly Maintenance

• Test Output Signals
• Verify Distance Calculation
• Inspect Interface Connections

Annual Maintenance

• Clean Transducer Area
• Check Hull Penetration
• Verify Calibration
• Test Data Outputs

Dry Dock Maintenance

• Inspect Sensor Condition
• Remove Marine Growth
• Check Sealing Components

Proper preventive maintenance greatly extends equipment lifespan.

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Speed Log Sensors & Marine Applications

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Why Ships Still Use Speed Logs

Although GPS provides Speed Over Ground (SOG), speed logs remain essential because:

• GPS Cannot Measure Speed Through Water
• Autopilot Systems Require Accurate Inputs
• ECDIS Benefits From Water Speed Data
• Fuel Optimization Requires Speed Analysis
• Harbor Maneuvering Depends on Accurate Speed Information
• Regulatory Requirements Still Support Log Data Usage

As a result, speed logs remain a critical part of modern bridge navigation systems.

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Frequently Asked Questions (FAQ)

What is the Yokogawa EML-500?

It is an electromagnetic marine speed log used for measuring vessel speed through water and travelled distance.

What does the EML-500 measure?

The system measures:

• Speed Through Water (STW)
• Distance Travelled
• Navigation Speed Data

Is it compatible with ECDIS?

Yes. The EML-500 can provide speed information to ECDIS systems.

Can it interface with VDR systems?

Yes. Speed data is commonly recorded by Voyage Data Recorders.

Why is Speed Through Water important?

It helps navigation officers understand vessel performance independent of current and tidal influences.

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Short Product Description

The Yokogawa EML-500 Speed Log is a professional marine speed measurement system designed to provide accurate vessel speed-through-water and distance information. Widely used aboard commercial vessels worldwide, it supports ECDIS, AIS, VDR, radar, and integrated navigation systems while delivering reliable long-term performance.

SM MARINE SERVICE™

Marine Automation & Navigation Equipment Supplier

Available Condition:

• New Equipment
• Used Equipment
• Refurbished Equipment
• Reconditioned Equipment

Stock Location:

• Bangladesh
• China

Services:

• Worldwide Shipping
• Technical Support
• Spare Parts Supply
• Marine Equipment Sourcing

Contact Information

SM MARINE SERVICE™
Samir Market, DT Road, Pahartali, beside CDA Market, Chattogram, Bangladesh

Mobile / WhatsApp / Viber: +88 01818 929292

Email: info@smmarineservice.com

Website: www.smmarineservice.com

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