PNI TCM - Manual (Page 25)

PNI Sensor Corporation DOC#1014688 r06
TCM User Manual – July 2013 Page 20
Note: While the TCM is shown removed from the host system, the Accelerometer
Calibration may be performed with the TCM mounted in the host system.
Figure 5-2: Accelerometer Calibration Starting Orientations
5.2.2 Mag-and-Accel Calibration
The TCM allows for a simultaneous magnetometer and accelerometer calibration. This
requires a full-coverage calibration pattern, physically stable measurements, and
installation in the user’s system so the host system’s magnetic signature is present. PNI
recommends 18 to 32 calibration points for a Mag-and-Accel Calibration. The
Accelerometer-Only Calibration pattern discussed in Section 5.2 will work for a Mag-
and-Accel Calibration. Optimal performance is obtained when all rotations of the TCM
are performed towards magnetic north to achieve the widest possible magnetic field
distribution.
Note that combining calibrations only makes sense if all the host system’s magnetic
distortions (steel structures or batteries, for instance) are present and fixed relative to the
module when calibrating. If an Accelerometer-Only Calibration is performed, the user’s
system distortions are not relevant, which allows the TCM to be removed from the host
system in order to perform the Accelerometer-Only Calibration.