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Main obstacles to electric compass precision

 

The main obstacles to electric compass precision are as follows.

Major Causes of sensor accuracy deterioration and countermeasures

 

 
  Cause Countermeasure
Compass unit sensor's incorrect sensitivity and/or origin setting Use a standard magnetic field to calibrate. If such standard field generator is not available, use the calibration software.
Compass unit Sensor element mounting alignment errors in the compass package Use the standard magnetic field to calibrate the sensor element orthogonality.
Compass unit Electric noise from compass internal circuit

When the accuracy is not satisfactory even if the internals noise is within the product specification, apply software filter processing.

Compass unit Sensor temperature characteristics Temperature compensation is already done in the compass internal circuit. If the accuracy is still not satisfactory, a solution to maintain a constant ambient temperature is required.
Compass unit Effects due to moisture When moisture is absorbed, the sensors' sensitivity and origin may change.
Keep the compasses in the inside of the ship out packages until the compass mounting.  If a compass absorbs moisture, return it to the equilibrium state and calibrate.
Platform Magnetic noise from ferrous materials in the housing/PCBs

For connectors, IC leads, springs, screws, reinforcing plates, antennas and other materials with high hysteresis, check the guidelines, and avoid their proximity. If you are unable to avoid proximity, calibrate.
(Electric products often have nickel plated parts or nickel alloy leads, so these items have at least trace magnetic fields).

Platform Magnets For magnets in the detachable covers, speakers, oscillating motors, cooling fans, and the like, check the guidelines and avoid their proximity.
Platform Effects of wiring with strong electric current The relationship between current, magnetic fields, and distance are determined, according to the amperage laws. Avoid areas with wiring carrying strong electric current.
Platform Housing orientation and vibration

It can be influenced by the movement of the case in which the sensor is mounted. Where possible, use without moving.
In the case of a mobile device, it is almost impossible to avoid small hand movements and vibrations, so use software filter processing.

Platform Assembly errors Please be careful of mounting errors when the sensor is mounted on a circuit board or assembly errors stemming from when the circuit board is put in a case. When these can't be avoided, calibrate.
Platform - ※If a flexible circuit board is used where the sensor is able to be adjusted and not directly mounted on the circuit board, adjustment is much easier.
External causes The Earth's magnetic field and its deviation When measuring magnetic fields, the earth's magnetic field will always interfere.  As such, in order to exclude it, some solution like a magnetic shield must be used when measuring.
Also, when using the electric compass, it will have declination stemming from the Earth's magnetic field deviating from due north, so calibration is necessary. Use calibration software.
External causes Magnetic fields from being close to physical body and metal products. For belts, mobile phones, wristwatches, check the guidelines and avoid proximity when possible. When unavoidable, there are no countermeasures and the software will display a warning regarding worsening accuracy.
External causes A room's magnetic field and metal products For steel desks, chairs, speakers, electric fans, check the guidelines and avoid proximity when possible. When unavoidable, there are no countermeasures and the software will display a warning regarding worsening accuracy.
External causes Wiring with strong current or high voltage For high voltage, check the guidelines and avoid proximity when possible. When unavoidable, there are no countermeasures and the software will display a warning regarding worsening accuracy.
External causes Magnetic fields of vehicles and metal products For cars, trains, elevators, check the guidelines and avoid proximity when possible. When unavoidable, there are no countermeasures and the software will display a warning regarding worsening accuracy.
External causes Buildings and structures For rebar buildings, metal bridges, and structures, check the guidelines and avoid proximity where possible. When unavoidable, there are no countermeasures, and the software will display a warning regarding worsening accuracy.
External causes - ※External causes such as when GPS is nonfunctional inside a building or underground are a foundational problem so there are no countermeasures.
Examples of metal materials and soft magnetic materials

・In connector terminals, the gold plate's nickel base coat
・Nickel plated IC leads will have a magnetic field
・In springs, many metal alloys that have good elasticity also have magnetic fields
・In screws and reinforcing plates, the inexpensive types of stainless steel have magnetic fields
・In antennas, shape memory alloy antennas and the like have many varied properties
・In hinges and slides, the metal alloys in the bending mechanisms