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Lab #1

Magnetic compasses UKP-M and KMO-T

Objective:

1. To study the principle of operation and the device of the UKP-M magnetic compass.

2. To study the principle of operation and the device of the magnetic compass KMO - T.

Lesson plan

1. Familiarization with the principle of operation and the device of the UKP-M magnetic compass.

2. Familiarization with the principle of operation and the device of the KMO magnetic compass - T.

Theoretical Provisions

The design of the UKP-M magnetic compass

Magnetic compasses are used on ships as a course indicator, as well as to determine the position of a ship in the sea according to the bearings of coastal landmarks and celestial bodies. The compass used for direction finding and course control is called main. It is installed on the upper bridge in the center plane of the ship or, as an exception, near it. The compass located in the wheelhouse, according to the indications of which the helmsman keeps the ship on a given course, is called track.

The sensitive element of the UKP-M magnetic compass is a six-needle magnetic system (Fig. 1.1), placed in a kettle with supporting fluid. The sensing element has a circular scale for reading the ship's heading. The magnetic system with a scale is called magnetic compass card, centered with a pin.

Since the ends of the arrows 1 are on the same circle and at predetermined angles with respect to the diameter of their magnetic system, then with sufficient accuracy for practice, the automatic destruction of the deviation coefficients of higher orders is achieved. This circumstance allows in all cases of ship practice to be limited to determining the residual deviation of the compass only on eight equally spaced compass or magnetic courses.

In addition, such an arrangement of the arrows also achieves equality of the moments of inertia of the card relative to any equatorial axis of its disk with divisions, which eliminates random oscillations of the card itself during the ship's motion.

Fig.1.1 Magnetic compass card

The frame of the card (Fig. 1.1) consists of a float 2 , made of thin sheet brass with a rim, a cone 7 equipped with an agate firebox 3 and fixing screw 4 to her, a paper disk 5 and platter 6 . Cone 7 serves to ensure that the card could acquire on a pin screwed into the column of the bowler to failure, the angle of inclination ≤ 12 °, without touching this column.

paper disc 5 divided into 360 ° through 1 °, and the numbers indicate tens of degrees, starting from 0 °. Latin letters indicate the main and quarter rumba.

The compass bowl with the liquid in which the card is located is installed in a gimbal suspension in the upper part of the binnacle, designed to suspend the magnetic compass and place the deviation device. The binnacle is attached to the upper deck and, as a rule, is located in the diametrical plane of the vessel. This location provides the most favorable magnetic conditions for the operation of a magnetic compass.

On the side wall of the kettle there is a hole closed with a screw plug. Through the indicated hole, the kettle is filled with a supporting liquid (an aqueous solution of ethyl alcohol with a strength of 43º), which does not freeze up to -26º. If there are air bubbles in the main chamber of the kettle, they must be removed. To do this, the compass bowl is carefully turned over with a glass lid down and swayed around a horizontal axis, or, having removed the light bulb cartridge from the cup with the load, lightly press the diaphragm plug several times. If these measures do not desired result, then add a certain amount of compass liquid to the kettle.

The compass kit includes a direction finder - a device for finding direction of objects and celestial bodies, as well as for determining heading angles.

A magnetic compass installed on a non-magnetic vessel shows a magnetic heading ( MK ), which differs from the true course ( IR ) by the magnitude of the magnetic declination d :

IR = MK + d(1.1)

Ship iron affects the readings of the magnetic compass. In his countdown - compass course ( QC ) - an error appears, called deviation δ . The total magnetic compass correction will be

∆ = d + δ.(1.2)

The true course of the ship is determined from the expression

IC = QC + ∆, (1.3)

IC = QC + δ + d(1.4)

compass course ( QC ) corrected by deviation δ , determines the magnitude of the magnetic course ( MK ),

MK = KK + δ(1.5)

On fig. 1.2 shows relations (1.1)-(1.5). Magnetic compass deviation δ - This is the error, which includes four of its components:

- permanent deflection arising from soft iron;

- semicircular deviation, due to the influence of mainly solid marine iron;

- quarter deviation, caused by soft ship iron;

-roll deviation, which occurs when the ship rolls and rolls, and is mainly due to the action of the vertical ferromagnetic elements of the ship's hull.

To destroy these three deviations in the design of the magnetic compass, there are three independent devices.

Semicircular deviation compensators - two pairs of permanent magnets-destroyers installed inside the compass. One pair is longitudinal magnets, the other is transverse. The elimination of semicircular deviation consists in finding the proper position of the magnets using carriages or flywheels. AT and FROM .

Compensators of the fourth deviation are made in the form of horizontal plates made of soft ferromagnetic material, which are installed from the outside of the binnacle, in its upper part.

A vertical permanent magnet for the elimination of roll deviation is placed inside the binnacle in a deviation pipe. Flywheel Z set it to its proper position.

The magnetic compass makes it possible to determine not only the course of the vessel, but also the heading angle and bearing of any object.

Magnetic compass checks

Checking the card for stagnation

Stagnation of the card is caused by dry friction in the suspension of the sensing element. To determine the amount of stagnation, the card is deflected at a small angle, acting on it with some kind of magnet. After the magnet is removed, it should return to the original countdown. In the presence of stagnation, the card will be installed in a different position. The difference between readings characterizes the amount of stagnation.

To increase the accuracy of determining the angle of stagnation, the readings on the card are measured through the prism of the direction finder. The work is carried out on the shore in the following sequence:

– set the direction finder to the 0° reading along the azimuthal circle and turn the compass binnacle so that the 180° reading is under the direction finder prism ( S) potatoes.

- acting with a small magnet, they deflect the card by 2 - 3 degrees, remove the magnet and, after the card calms down, take a reading under the prism of the direction finder (with an accuracy of 0.2 °); the procedure is repeated several times;

– find the angle of stagnation as the average difference of readings compared to the initial value of 180°.

Stagnation of the card is considered normal if the angle of stagnation does not exceed 0.2 °. With a large stagnation, it is necessary to sharpen or replace the compass pin.

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Purpose

Continuous indication of the course, heading angles and directions to various visible objects or celestial bodies. It is installed on ships of all classes.

Principle of operation and brief description

The principle of operation is based on the property of the magnetic needle to be installed in the plane of the magnetic meridian. In a 127-mm magnetic compass, the sensitive element is a float with a scale, to which 6 thin magnets are attached from below, located symmetrically with respect to the N-S scale line. The float is supported by a special device - a firebox - on a compass pin installed in the center of the pot filled with liquid, and can rotate freely. The bowler hat is placed in a binnacle - a special pedestal - with the help of a gimbal suspension, in such a way that the plane formed by the course threads fixed in the bowler hat is directed along the diametrical plane of the ship. The division on the scale of the card, against which the course thread of the bowler is set, will be the reading of the compass course.

127 mm compasses are available in three versions:
UKP-M1 - 127-mm marine magnetic compass on a high metal binnacle with a protective cap and an electric lighting device;
UKP-M3 - 127-mm marine magnetic compass on a low metal binnacle with a protective cap and an electric lighting device;
· UKP-M10 - 127-mm marine magnetic compass on a desktop plate with a blind cap and an electric lighting device.

All compasses are equipped with a device for the destruction of magnetic deviation - semicircular, quarter and roll. In the high and low binnacles, a place is provided for installing an electromagnetic compensator, which is part of the compensating devices (KUS-9U, KUS-9M, KUS-12U) and serves to compensate for electromagnetic deviation. The compass kit includes a visual direction finder, and to facilitate reading when using the compass as a traveling compass, a compass magnifier can be installed on the kettle.

Technical details

Card scale diameter 127 mm, division value 1°.
The stagnation of the card with a horizontal component, a magnetic field H - 0.05 Oe and a temperature from 15 to 20 ° C is not more than ± 0.2 °.
The half-cycle of oscillations of the card at H = 0.175 Oe and a temperature of 15 to 20 °C is 10.8 ± 1.5 s.
Accuracy of reading on the scale of the card through the prism of the direction finder is ±0.2°.
The kettle is filled with a 43% aqueous solution of ethyl alcohol. The freezing point of the liquid is minus 25 °C. The lighting device of the compass card scale is designed for 6, 12 or 24 V direct current or alternating current. A converter is used for a 110 or 220 V DC on-board network, and a transformer for a 127/220 V AC on-board network. The power consumed by the lighting device is from 4.5 to 6 W when powered through a converter or transformer - 12 W.

The accuracy characteristics of the compass do not change under the following conditions:
temperature from minus 24 to 50 °С;
Relative humidity up to 98% at temperatures up to 40 °C.