Digital Magnetic Compasses (DMCs) provide valuable navigation solutions, but they are sensitive to magnetic influences, causing inaccuracies in determining north direction. In this article, we deal with the challenges posed by numerous magnetic influences of a host system on DMCs and explain a easy solution to compensate for them with System State Compensation (SSC).
Integrating a DMC within a complex host system often leads to unforeseen challenges, particularly in compensating for magnetic effects. Within a host system, a multitude of magnetic influences originating from currents or materials are typically present at various times, which influence the DMC’s ability to find north. All these influences can be identified within the host system, and the SSC feature is capable of neutralizing the various magnetic effects stemming from hard magnetic materials or currents. Not all materials create equal disturbances; hard magnetic materials show a greater deviation compared to soft magnetic materials (see info box).
Hard & soft magnetic materials
Magnetic materials fall into two categories: soft and hard. Soft magnetic materials, like iron-silicon alloys and iron-nickel alloys, can be easily magnetized and exhibit a DMC deviation of 1°-3°. On the other hand, hard magnetic materials, including steel and alloys containing aluminium, nickel, cobalt, and copper can be magnetized permanently through strong magnetic fields, with a DMC deviation range of 3°-30°.
Example for showing the operating principle of SSC:
Magnetic influence of Thermal Imaging (TI) in a handheld system
Challenge:
The operation of a Thermal Imaging (TI) channel within a handheld device affects the DMC’s azimuth reading due to the flowing current. During the day, the optical sight is employed without any current flow, and therefore, the DMC‘s north finding is perfect. However this changes if the TI sensor is activated, as an electric current flows, which disturbs the magnetism and affects the DMC’s north finding accuracy.
Solution:
Implementing the System State Compensation function in DMC pico allows to neutralize various host system modes and their respective states. In this simple example, there is only one TI mode with two states: State1 = “TI switched off” and State2 = “TI switched on”. The offsets for these states need to be prepared in advance and SSC stored them in the DMC pico. Now, when the handheld device is used with the TI channel, the corresponding state is activated via the DMC interface software. The DMC automatically adjusts by adding or subtracting the correct offset to compensate for the magnetic impact of the TI current. This means, whenever the TI channel is activated and current flows, the DMC pico automatically compensates to ensure precise north finding.
Easy and fast preparation:
Preparing the states and DMC offset values for SSC is an easy and fast process. Following a basic 12-point compensation procedure, various modes can be selected, such as TI activation, GPS, Bluetooth, and any combination of these. For each mode, the DMC Pico autonomously determines seamlessly the hard magnetic offset value to ensure accurate north finding every time.
This process is very easy to use as only one 12pt compensation is needed for as many states as the system requires.
Efficient neutralization of magnetic influences with SSC:
This straightforward process significantly contributes to the overall ease of use of the SSC. By conducting just one 12-point compensation process, the DMC Pico is ready to neutralize as many states as required by the host system -and in today’s systems, there are often many states needed. The result is for all cases improved north finding accuracy for the user.
Note:
This simple example explains the operating principle of SSC for just one sensor. In today’s host systems usually there are often many more sensor used. The standard DMC-pico has already 6 in-built stores for saving 6 offset-modes and each mode has to be prepared with a single 12pt compensation – so SSC contributes to overall ease of use by eliminating the need for more than one compensation.