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Laboratory work No. 1

Magnetic compasses UKP-M and KMO-T

Goal of the work:

1. Study the principle of operation and structure of the UKP-M magnetic compass.

2. Study the principle of operation and structure of the KMO-T magnetic compass.

Lesson plan

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

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

Theoretical provisions

Design of the UKP-M magnetic compass

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

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

Since the ends of the arrows 1 are on the same circle and at given angles with respect to the diameter of their magnetic system, then this automatically eliminates the deviation coefficients of higher orders with sufficient accuracy for practice. This circumstance allows in all cases of shipboard practice to limit ourselves to determining the residual deviation of the compass only on eight equally spaced compass or magnetic courses.

In addition, this arrangement of the arrows also ensures equality of the moments of inertia of the card relative to any equatorial axis of its disk with divisions, which eliminates random vibrations of the card itself during the rocking of the ship.

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, cone 7 equipped with an agate firebox 3 and fastening screw 4 to her, a paper disk 5 and support disk 6 . Cone 7 serves so that the pot can acquire an inclination angle of ≤ 12° on a pin screwed into the pot column completely, without touching this column.

Paper disk 5 divided into 360° every 1°, with numbers indicating tens of degrees, starting from 0°. Latin letters indicate the main and quarter directions.

The compass pot with the liquid in which the card is located is installed in a gimbal suspension in the upper part of the binnacle, intended for suspending the magnetic compass and placing a deviation device. The binnacle is attached to the upper deck and, as a rule, is located in the centerline of the ship. This arrangement provides the most favorable magnetic conditions for the operation of a magnetic compass.

There is a hole on the side wall of the pot that is closed with a screw cap. 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 down to -26º. If there are air bubbles in the main chamber of the pot, they must be removed. To do this, the compass bowl is carefully turned over with the glass lid down and rocked around the horizontal axis, or, after removing the light bulb socket from the cup with the weight, lightly press the diaphragm plug several times. If these measures do not give desired result, then you should 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 mounted on a non-magnetic ship shows the magnetic heading ( MK ), different from the true course ( IR ) by the magnitude of magnetic declination d :

IR = MK + d(1.1)

Ship's iron affects magnetic compass readings. In its reference - compass course ( QC ) – an error appears, called deviation δ . The general correction of the magnetic compass will be

∆ = d + δ.(1.2)

The true course of the vessel is determined from the expression

IR = CC + ∆, (1.3)

IR = CC + δ + d(1.4)

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

MK = KK + δ(1.5)

In Fig. 1.2 presents relations (1.1)-(1.5). Magnetic compass deviation δ - This is an error that includes four components:

- constant deviation, arising from soft iron;

- semicircular deviation, caused mainly by the influence of solid ship iron;

- quarter deviation, caused by soft ship's iron;

-roll deviation, which occurs during the roll and pitching of the ship, and is mainly caused by the action of the vertical ferromagnetic elements of the ship's hull.

To eliminate these three deviations, the design of the magnetic compass has three independent devices.

Semicircular deviation compensators - two pairs of permanent destroyer magnets installed inside the compass. One pair is longitudinal magnets, the other is transverse. Eliminating semicircular deviation involves finding the proper position of the magnets using carriages or flywheels IN And WITH .

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

A vertical permanent magnet for eliminating heel deviation is placed inside the binnacle in the deviation pipe. Flywheel Z set its appropriate position.

A magnetic compass makes it possible to determine not only the course of a ship, 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 sensitive element. To determine the amount of stagnation, the card is deflected at a small angle, influencing it with some kind of magnet. After the magnet is removed, it should return to the original reading. If there is stagnation, the card will be installed in a different position. The difference in readings characterizes the amount of stagnation.

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

– set the direction finder to a reading of 0° in the azimuthal circle and turn the compass binnacle so that a reading of 180° appears under the direction finder prism ( S) cards.

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

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

The stagnation of the card is considered normal if the stagnation angle does not exceed 0.2°. If there is a lot of stagnation, it is necessary to sharpen or replace the compass pin.

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Purpose

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

Operating principle and brief description

The principle of operation is based on the property of a 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 below, located symmetrically relative to the N - S scale line. The float is supported by a special device - the firebox - on a compass pin installed in the center of a pot filled with liquid and can rotate freely. The bowler, using a cardan suspension, is placed in the binnacle - a special cabinet - so that the plane formed by the course threads fixed in the bowler is directed along the center plane of the ship. The division on the card scale, against which the kettle's course thread is installed, will be the compass heading count.

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 tabletop plate with a blank cap and an electric lighting device.

All compasses are equipped with a device for eliminating magnetic deviation - semicircular, quarter and roll. In the high and low binnacles there is space 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 taking readings when using the compass as a guide, a compass magnifying glass can be installed on the bowler.

Technical data

The diameter of the card scale is 127 mm, the division value is 1°.
Stagnation of the card with a horizontal component, a magnetic field H - 0.05 Oe and a temperature from 15 to 20 ° C no more than ±0.2 °.
The half-cycle of oscillations of the card at H = 0.175 Oe and a temperature from 15 to 20 ° C is 10.8 ± 1.5 s.
The accuracy of reading on the card scale through the direction finder prism is ±0.2°.
The pot is filled with a 43% aqueous solution of ethyl alcohol. The freezing point of the liquid is minus 25 °C. The compass card scale lighting device is designed for power supply with direct or alternating current voltage of 6, 12 or 24 V. For an on-board DC network with a voltage of 110 or 220 V, a converter is used, and for an on-board AC network with a voltage of 127/220 V, a transformer is used. The power consumed by the lighting device is from 4.5 to 6 W when powered through a converter or transformer - 12 W.

The compass accuracy does not change under the following conditions:
· temperature from minus 24 to 50 °C;
· relative humidity up to 98% at temperatures up to 40 °C.