What Is a Compass Inclinometer?

The geological compass is an indispensable tool for geological work in the field. It can be used to determine the direction, the location of the observation point, and measure the spatial position of any observation surface (such as the rock layer level, the fold axis surface, the fault plane, the joint surface, etc.), and determine the igneous rock. Various structural elements, the occurrence of ore bodies, etc. So you must learn to use a geological compass.

Geological compass

Structure of geological compass: There are many types of geological compass, but the structure is basically the same. We usually use the circular basin geological compass. It consists of magnetic needle, dial, inclinometer, aiming plate, level, etc. installed in a copper, aluminum or wooden round basin, as shown in the figure.

1 Test conditions: including trend, tendency, inclination;

2 rough terrain survey: including fixed orientation (that is, fixed point of intersection), slope angle measurement and fixed level;

3Measure the vertical angle.

1. The magnetic needle damping time (the time when the magnetic needle is deflected by 90 ° to stay in the original position) is 30-60 seconds.

2. Reading error:

a) The error of the degree indicated before and after the magnetic needle rotates is not more than 0.5 °;

b) The error of magnetic needle at 0-180 °, 90-270 ° due to eccentricity is not more than 0.5 °;

c) The reading error of the goniometer is not more than 0.5 °

3. Level sensitivity:

a) Long level is 15 ± 3 / 2mm

b) Circular level is 30 ± 5 / 2mm

Principle : The instrument uses a magnetic object (that is, a magnetic needle) to indicate a certain direction of the magnetic meridian. With the reading of the scale ring, the direction of the target relative to the magnetic meridian can be determined. Based on the two selected measuring points (or known measuring points), the position of another unknown target can be measured.

Structure (reference structure diagram)

The instrument is composed of an upper cover 6 and a casing 13 through a joint 8 to form an instrument main body. A reflector 7 is installed in the upper cover, so that the target can be reflected in the mirror. A long sight 1 is mounted on the outside of the casing 13, and a small sight 5 can be used to aim at the target. A scale 2 and a magnetic needle 3 are installed in the housing, which can directly read the azimuth value of the target, and the circular level 10 can indicate the horizontal position of the instrument. The long level 4 and the indicating plate 11 are used for measuring the slope angle, and can be directly read on the inclination scale of the steering wheel 12. The switch 9 is a magnetic needle brake mechanism, and a magnetic declination adjustment shaft is provided on the outside of the casing. The instrument has the characteristics of compact structure, small size, convenient carrying, reliable accuracy and stable performance.

The magnetic declination must be corrected before use.

Because the geomagnetic north and south poles do not exactly coincide with the geographic north and south poles, that is, the magnetic meridian does not coincide with the geographic meridian, the magnetic north direction of any point on the earth does not coincide with the north direction of that point, and the angle between the two directions Called magnetic declination.

The east of the magnetic needle at the north end of a point on the earth is eastward, and westward is westward. East bias is (+) West bias is (-).

1. The magnetic needle, thimble and agate bearing are the main parts of the instrument. They should be carefully protected and kept clean to avoid affecting the sensitivity of the magnetic needle. When not in use, the instrument should be shut down securely. After the instrument is turned off, the magnetic needle is automatically lifted by the action of the switch and the lever to disengage the thimble from the agate bearing, so as not to damage the thimble.

2. Do not disassemble all hinges easily, so as not to affect accuracy.

3. The instrument should avoid high temperature exposure as much as possible, so as to prevent the air bubbles from leaking and malfunctioning.

4. The rotating part of the hinge should often be ordered with some watch oil to prevent it from being broken by dry grinding.

5. When not used for a long time, it should be placed in a ventilated and dry place to avoid mold.