How to choose an electronic compass ?

There are a lot of people in the choice of electronic compass do not know how to choose, sometimes because did not consider the following content, and choose the wrong electronic compass, resulting in a waste of time and money, let us to see some tips when choose an electronic compass. 

First, let's take a look at what an electronic compass, also known as a digital compass, is a way of locating the North Pole using the geomagnetic field.

Secondly, as an important navigation and orientation tool, electronic compass is increasingly used in navigation and orientation systems.Most current navigation systems use an electronic compass to indicate direction.The electronic compass can accurately output Azimuth, pitch, Roll and other parameters by calculating the earth's magnetic field and gravitational field.

Known the basic concept of the electronic compass, now let's take a look at the electronic compass types on the market, manufacturers, many models, in the face of these we may look confused, so how to distinguish the performance of the electronic compass, how to choose a suitable for your application of the electronic compass?What's the difference between a good compass and a bad compass?

The main difference between electronic compasses is the difference in accuracy, namely the accuracy of heading, pitch and roll, and especially the accuracy of heading.The heading is defined as the Angle between the projection of the compass's axis on the horizontal plane and the north direction, the pitch is defined as the Angle between the compass's axis and the ground plane, and the roll is defined as the Angle at which the compass rotates about its axis.As shown in the figure below

According to the above definition, if the compass changes only in pitch, then its output azimuth and roll Angle should remain the same.In the same way, if a compass rolls about itself, that is, on its axis, the azimuth and pitch angles of its output should remain the same.In the use of compass, such as used in vehicles, antenna orientation and surface buoys and many other occasions, the carrier will often tilt back and forth, when used in petroleum, geological logging, often rotation, so most applications require compass to meet the requirements of tilt and roll orientation will not change.

Another requirement for compass accuracy is that the output of the compass should be 0 degrees if the current carrier is pointing north, and 90 degrees if the carrier is pointing east. The measured value and the true value should match exactly within the margin of error

For petroleum, geological, and coal logging, the orientation and inclination of the product should not change as the logging instrument rotates downhole, which is important for logging applications.

Another rule when choosing a compass is whether it is resistant to harsh conditions.A natural disadvantage of compasses is that they become less accurate in environments with magnetic interference.Compasses use the direction of the Earth's magnetic field to determine orientation. If the Earth's magnetic field is disturbed or distorted, the accuracy of orientation measurement will be reduced.Iron materials, batteries, motors, high currents, and so on can interfere with the geomagnetic field, and the closer these materials are to the compass, the worse the interference is.So if you want the compass to be accurate, you have to stay away from the source of the interference, but in many cases this is not possible.So the only way to solve this problem is to do magnetic calibration.In the process of magnetic calibration, the compass rotates with the measured object (i.e., the interference source) in a certain way and learns the surrounding magnetic environment to distinguish which is magnetic interference and which is geomagnetic field. Through this learning, the interference is eliminated and the high-precision azimuth output is obtained.