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Yokogawa Denshikiki Co., Ltd.


Electromagnetic Log

Electromagnetic Log System Descriptions

Electromagnetic Log System

Electromagnetic logs indicate water speed. Sensors in the ship hull use Fleming's rule.
There are two types of sensors (fore-and-aft) and dual-axis sensors (fore-and-aft andstarboard-and-port). In addition, various types of sea valves are available for installing sensors on the bottom of the hull. The sensor head extruded from the bottom is either 7mm or 50mm long type.

EML500: This type is suitable for general merchant vessels, and accepts both flush-mountable and dual-axis sensors.

EML50: This type is compact and can be mounted in many different ways.

System Configuration

The electromagnetic log system is configured as shown below and is suitable for a wide variety of vessels.

System Name Hull Type Sensing Axes Sensor Size Remarks
EML500 - HS1 Single bottom 1 35 mm dia.
- HD1 Double bottom 1 35 mm dia.
- HV1 Single bottom 1 70 mm dia.
- FA1 Single bottom 1 48 mm dia.
- HV2 Single bottom 2 70 mm dia.
- FA2 Single bottom 2 48 mm dia.

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System Configuration of EML500


Explanation of Units

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Explanation of Units

LT501 Master Unit
This unit consists of a terminal block and a signal processor.
Microprocessor and LSI based circuitry and the absence of moving parts ensure high reliability.

LR523 Master Indicator
This unit works as the control and display unit of the system.
The electromagnetic sensor can be backed up if the ground speed is supplied from a GPS receiver.

LR524/525 Analog Speed Indicators
These units are analog indicators for reading the vessel water speed. The LR524 is for a single-axis sensor,while the LR525 is for a dual-axis sensor.
There are six choices for the indicator speed range.

Various Sensors (LS501/531/541/542/571/572)
These sensors are used in the EML500 series.
The sensors have built-in preamplifier for stable and long-distance transmission of the current signal.

Flush-mounted Sensors
The 48mm or 70mm diameter sensor is flush-mountable and therefore suitable for highspeed vessels.
(The figure shows the sensor mounted on the bottom of a vessel.)

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