Magnetic compass according to the principle of the compass, used to indicate the direction of the instrument, also known as magnetic compass. It is mainly composed of a number of parallel magnetic needles, dial and magnetic error correction device. The magnetic needle is fixed on the back of the dial. Under the influence of geomagnetic field, the magnetic needle rotates with the dial to indicate the direction. It is often used for navigation on ships and aircraft.
Characteristic parameter Main technical parameters: Course measurement range: 0~360°. Angle measurement range: 0~180°. Course accuracy: ≤±1.5°. Inclination accuracy: ≤±0.2°. Stable time: ≥30 seconds. Size: 80mm×60mm×20mm(L×W×H) or customized. Power requirements Power supply: DC 12V. Working current: ≤100mA. Output interface Communication protocol: RS485, RS232 or custom. Working environment requirements: Operating temperature: -40℃ ~ + 50℃. Impact: triaxial 50g, 11ms, half sine. Random vibration: 0.04g/Hz,5 minutes.
The magnetic compass uses the inherent directivity of the geomagnetic field to measure the attitude Angle of space. It can measure the three-dimensional attitude data of the carrier: horizontal heading, pitch, roll. It can be widely used in situations where the attitude Angle of the platform (or carrier) needs to be obtained, such as navigation, oil drilling, underwater platform operation, aircraft attitude measurement, robot control and other fields. Digital magnetic compass has the advantages of small size, high course accuracy, wide tilt range, high frequency response and low power consumption, which is suitable for the occasions where the course accuracy is high and the power consumption and volume are limited. Principle Geomagnetic north and south and geographical north and south are very coincident, the direction of the free hanging magnetic needle and the geographical north and south (true longitude line) direction has a deviation Angle, that is, magnetic declination (also known as magnetic difference). In the specially drawn navigation map, the magnetic difference correction for each place is noted. The true course of the aircraft can be obtained by adding the magnetic heading reading and the magnetic difference algebra. The Angle between the intensity vector of the geomagnetic field and the horizontal plane is called the magnetic inclination. The magnetic inclination is not equal everywhere, and the closer you get to the geomagnetic pole, the greater the magnetic inclination. At high latitudes, the horizontal component of the geomagnetic field is very weak, and its directional effect on horizontally suspended magnetic bars is small. Therefore, in the polar regions of the Earth, magnetic compasses cannot be applied. In the aeromagnetic disk, a pair of permanent magnetic rods are suspended under the float ball, in a pendulum structure, so that the magnetic rods can remain horizontal. The float is supported by the tip of the shaft on the jewel bowl seat and suspended in the float (ethanol, light kerosene or other compass oil) to reduce friction with the support part. A bearing scale ring is attached to the magnetic bar and the float. The heading mark representing the nose direction relative to the reading of the bearing scale ring is the heading of the aircraft. The floating liquid will expand and contract when the ambient temperature changes, so the expansion chamber is used to compensate. Due to the interference of the magnetic field formed by the steel components and electrical equipment on the aircraft, the magnetic rod will be stabilized in the orientation of the magnetic field (compass longitude) of the composite magnetic field of the horizontal component of the geomagnetic field and the horizontal component of the aircraft magnetic field. The deviation Angle between compass north and magnetic north is called compass difference. The same aircraft has different values of difference in different directions. In order to correctly measure the magnetic heading of the aircraft, a compass corrector is installed on the shell of the magnetic compass to generate an artificially compensated magnetic field that can be adjusted arbitrarily to weaken or offset the interference of the aircraft magnetic field. The magnetic compass should be installed in the machine where the magnetic interference is weak.
Sort There are 2 basic types of airborne magnetic compasses: ① Direct reading type: the advantage is simple and reliable, but because it is installed in the cockpit with large magnetic interference, the gap is larger. ② Far-reading type: the magnetic compass is changed into a magnetic heading sensor, which is installed outside the cockpit, and the detected magnetic heading information is transmitted to the heading indicator and displayed at a distance. Its advantage is that the magnetic sensor can be installed in the position of the aircraft with less magnetic interference, such as the wing tip, the tail, etc., to reduce the error. The common disadvantage of these two kinds of magnetic compasses is that when the aircraft is flying at non-uniform speed or turning or circling, the magnetic sensitive element deviates from the horizontal plane and is subjected to the action of the geomagnetic vertical component, which will produce large acceleration error and turning error; Due to the damping effect of liquid on the magnetic sensor, the significant lag error will occur when the aircraft changes course. Magnetic compasses are not suitable for use in areas with magnetic anomalies and high latitudes. Gyro magnetic compasses solve these problems successfully. The direct-reading magnetic compass is simple and reliable, and is used as an emergency instrument in many aircraft, in addition to being still used in small aircraft. Far-reading magnetic compasses have been replaced by gyro magnetic compasses or heading systems with better performance.
