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an instrument for measuring the magnetic dip, that is, the angle between the geomagnetic field vector and the horizontal plane. The direct measurement of dip is usually made using a dip needle or earth inductor.
A dip needle is a magnetic needle with a horizontal axis of rotation passing through the needle’s center of gravity. When measuring the dip, the direction of the axis at which the arrow rests vertically is found, and then the arrow is set to the magnetic meridian by rotating the arrow’s axis of rotation by 90°. The angle between the direction of the arrow’s magnetic axis and the horizontal plane corresponds to the dip at the point of measurement. The maximum accuracy of the determination of dip using a dip needle does not exceed ± 2’.
The operating principle of an earth inductor is based on the appearance of an electromotive force (or induction current) in a coil rotating in the earth’s magnetic field. The emf in a coil is absent only when its axis of rotation is directed along the magnetic field vector. The lack of current in the coil is recorded by means of a galvanometer. The accuracy of the earth inductor’s determination of dip may be as high as tenths of an angular minute. There are also other types of inclinometers. Because an inclinometer cannot always provide the needed accuracy of measurement, the dip is most often calculated on the basis of the results of measurements of the magnitudes of the total vector of magnetic field intensity and its components (horizontal and vertical).
REFERENCESIanovskii, B. M. Zemnoi magnetizm, 2nd ed. Moscow, 1953.
Afanas’ev, Iu. V. Ferrozondy. Leningrad, 1969.
IU. A. BURTSEV
a device for determining the angle and azimuth of curvature of a well or borehole in order to check its spatial attitude. Inclinometers are divided into two groups according to the method of measurement: direct-measurement instruments, using the earth’s gravitational field or the geomagnetic field, the gyroscopic effect, and telemetric sounding; and indirect-measurement instruments, using methods of orientation from the surface, successive trips, seismic surveying, radiolocation, and the magnetometric method. The measurements may be recorded directly in the inclinometer (by mechanical photographic, electrometric, or chemical methods) or by remote control.
Of the numerous inclinometer designs developed in the USSR, the most widely used are the IK-2, IT-200, and UMI-25 multiple-point models and the single-action ZI-1M and ZI-2. The IK-2 inclinometer consists of a down-hole unit (sensor) and a surface recording station (control panel). The position of the inclinometer is determined by three sensitive elements: the frame, the plumb, and the compass. A rheostat with a slide, whose resistance is proportional to the angular (azimuthal) deflection of the hole’s axis from the vertical at a given point, is connected to the metering circuit of the control panel by means of a commutator and brushes located in the upper part of the frame. The angle and azimuth are fixed by a switch gear activated by an electromagnet. The diameter of the down-hole unit is 58 mm; the measuring range of the angular deflection from the vertical is 0°–50°, and the range for the azimuth is 0°–360°. The error of measurement of angular deflection is no more than ±0°30’, and that of azimuthal deflection is no more than ±4° The down-hole unit is remotely controlled by logging cable.
REFERENCESMikhailovskii, V. N., and S. K. Ivanov. Izmerenie krivizny skvazhin. Kiev, 1960.
Kalinin, A. G. Iskrivlenie burovykh skvazhin. Moscow, 1963.
A. G. KALININ
an instrument for measuring a ship’s heeling angle. Inclinometers are based on the plumb, level, or vertical gyroscope principles. The simplest and most widely used inclinometer consists of an arrow indicator that rotates freely in the transverse plane of the ship and registers on a graduated scale. When the ship lists, the arrow responds to the force of gravity and keeps its vertical position, thus indicating the angular deviation of the scale to one side or the other, that is, the ship’s heeling angle. Less commonly used are fluid inclinometers constructed on the level principle. To measure list during rolling, inclinometers are used that make photographic records of the angles of deviation of the axis of the instrument from the horizon. Inclinometers are installed in the control room.