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Ruian Shunfeng Navigation Instruments Co.,Ltd

Add: No.20, Heping Road, Jinhu Street, Ruian, Zhejiang, China
Con: april Zhang
Tel: +86-577-65520898
Fax: +86-577-65966926
Mob: +8618158321811

Dead Reckoning Instruments.

For dead reckoning equipment. There are compass, log, autopilot, trace recorder, etc.

1. Compass: instruments that determine the direction and direction of the object. The ship is equipped with gyro compass and magnetic compass. The former is precise and convenient, while the latter is simple and reliable. The compass and the same as the most important navigational tools, after drawing the route on the chart, the ship depends on the compass direction, along the route to the destination.

The magnetic compass is made by the use of a magnetic needle pointing north. The compass is the original type of magnetic compass, one of the four great inventions of ancient China. The compass for sailing is also called a compass. After the arrival of the iron ship, the magnetic field produced a deviation. Since the 19th century, the method of eliminating deviation has been proposed successively. By the beginning of the 20th century, the liquid compass with stable performance and less friction was made and used for most ships. Magnetic compass has a magnetic difference, because the geomagnetic field is extremely inconsistent with the ground. The Angle between the magnetic north and the true north is the magnetic declination. The chart is marked with a magnetic difference and annual rate of change, and the magnetic compass can be used to correct the reading. The magnetic compass structure is mainly composed of the compass cabinet and the compass bowl, and the compass card with the magnetic needle is installed in the basin.

Gyro compass is also called the gyro compass, is the use of fixed axis of gyroscope and precession, combined with the earth's rotation vector and gravity vector, made from control equipment and damping devices to provide true north benchmark instrument. The gyro compass is composed of the main compass and the repeater, the power converter, the control box and the control box.

2. Log: instrument for measuring speed and cumulative range. It and the compass are the basic instruments for the dead reckoning, the work on the chart is based on the log reading on the route to take the navigation distance.

The theory and performance of modern log are mainly composed of the speed part and the indicator part. The speed measuring part is used to detect and amplify the ship's speed signal or voyage signal; Indicates that a ship's speed or voyage is displayed in mechanical or electrical form, and the voyage or speed is displayed by means of an integral or differential method. The working principle and performance of different types of log are described below.

The towed log. By using the current of the ship's navigation, the rotor of the aft tug is rotated, and the accumulative voyage of the ship is shown on the indicator by the log rope, the connecting hammer and the balance wheel. This kind of log linear difference, the high speed error is large, is affected by the airflow greatly, the operation is inconvenient, but the performance is reliable, some ships as the spare log.

A wheel log. Using the water flow relative to the navigation of the ship, the rotating wheel is driven, and the electrical impulse or mechanical intermittent signal is produced. After the electronic circuit is processed, the speed and range of the flight are given by the indicator. This kind of log is linear, the low speed sensitivity is high, but the mechanical part is easy to wear. In addition to the boat application, has gradually been phased out.

The water pressure log. Use relative to the dynamic pressure of navigation water, acting on the diaphragm chamber pressure conduction, converted to mechanical force measuring device, by means of compensation, converts mechanical force to speed, then through calculating speed device range is given. This kind of log work performance is reliable, but linear difference, low speed error is big, cannot measure backward speed, mechanical structure is complex, use inconvenience, gradually be eliminated.

The electromagnetic log. By cutting the magnetic field of the electromagnetic sensor at the bottom of the ship through the flow of water (conductor), the moving speed of the ship to the water is converted to the induction potential, and then to the speed and range. Its advantages are linear, high sensitivity, and can measure back speed, which is the most widely used.

It's called the doppler log. The doppler frequency shift between the transmitted sound waves and the underwater reflected waves is used to measure the speed and the cumulative range of the ship relative to the bottom. This type of log is accurate, sensitive, and can be measured vertically and horizontally, but is expensive. It is mainly used for the accurate data of the ship's longitudinal and transverse movement when the ship is sailing in the narrow waterway, entering and leaving the port and leaving the dock. When the doppler log is restricted to a depth of more than a few hundred meters, it can only use the water mass in the water layer as a reflection layer and become a water log.

The acoustic correlation log. The acoustic correlation principle is used to measure the time shift of the echo information from the same scattering source from the bottom to the two receivers. This kind of log can be measured backward speed and is used for sounding. The water depth of more than a few hundred meters also becomes relative to the water log, still in improvement.

Automatic steering gear: a device that can automatically control the steering gear (see) to keep the course, or automatic steering gear. At present, there are more electromechanical automatic steering instruments, which can adjust the rudder Angle, the rudder Angle and the Angle of the rudder according to the sea condition and the loading condition of the ship. The adaptive automatic steering instrument that appeared in the 1970s can automatically adjust the various rudder angles according to the objective situation, making the course more stable and the economic benefit is better.

4. Track recorder: an instrument that can automatically calculate the operation on the chart. It works according to the input of compass and log (or engine speed) information. In addition, there are sea chart equipment such as chart divider, nautical parallel ruler, navigation triangle, etc. Calculating tools such as slide rule, etc.