22
Optional Soft Iron Calibration
The above mentioned (C,Z) calibration routines do not compensate for soft iron
effects. Soft iron, batteries, wires with moving currents and other high permeability
materials in the near field cause these. These are generally far weaker than hard iron
effects. Choosing a good compass mounting location with distance from soft iron
structures should be attempted. In cases where the sensor will be impacted by soft
iron you should run the soft iron calibration (available starting with firmware version
1.4).
The soft iron compensation routine is started by hitting the <Esc> $ key command.
You want to select option 2 and follow the screen prompts (see example screen shot
below).
Important setup steps prior to running soft iron calibration:
Before starting the calibration, you need to have the system with the compass installed
and freshly calibrated, (via the <esc>C,<esc>Z commands). You must have
declination set to 0 before soft iron calibration begins, check setting by <esc>Q and
make change to 0 if necessary then hit <enter>. You will need to align the system to
the four cardinal points according to an accurate reference magnetic compass, 0 North,
90 East, 180 South, 270 West in an area free of magnetic disturbance. Once you have
your device or system properly aligned, starting at 0 North, you want to start the soft
iron correction with the <esc>$ command followed by entering 2. Actual calibration
routine shown below.
