CXM543 User’s Manual
Doc.# 6001-0015 Rev 1.2
Page 28
8.3
Hard Iron Commands
The hard iron correction procedures are described in the following sections.
The commands that are used with the 543 to complete the procedure are
described as follows:
?
Lists all commands recognized by the sensor, both those related to
hard iron corrections and those not related to hard iron.
HI
The hard iron correction is toggled on or off, if a correction is
available.
H2
2-dimensional data is to be collected, with the CXM543 prompting
the user with a set of good orientations. These orientations do not
need to be precisely met. If some data points have already been
gathered then this data is lost and the process starts all over. H2
uses 4 data points.
H3
3-dimensional data is to be collected, with the CXM543 prompting
the user as with H2. For H3, 6 data points are used.
HP
Records a hard iron data point using the present orientation. If an
H2 or H3 is being used to prompt the data, then the correction will
be calculated when the proper number of points have been
gathered. If neither H2 nor H3 has been used then data will be
gathered until the HC command is used, or the gathering of data is
aborted by means of the HQ command, or restarted by means of
the H2 or H3 commands.
HC
Calculates a hard iron correction using the data gathered so far.
The hard iron correction continues to be available until HC is used
again, even if the sensor has begun to accumulate data for another
correction. The command reports the “residuals” both with and
without the use of a hard iron correction. Small residuals indicate
a good fit to the data. A hard iron correction should be used when
the residual with hard iron is much smaller than the residual
without. If the residuals are comparable, this indicates that the
hard iron correction is too small to be determined with the data
gathered (and usually is sufficiently small that use of the correction
is not indicated).
HW#
Where, # is a number 0-10, hereinafter referred to as the weight.
This number sets the way corrections are calculated. The
corrections make maximal use of accelerometer data if the weight
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