PNI FieldForce Trax - Manual (Page 31)

PNI Sensor Corporation DOC#1016505 r06
TRAX User Manual Page 27
6.5.1 Calibration Settings
Calibration Type
The “Calibration Type” pull down menu establishes the type of calibration to be
performed. The options are Full, 2D, Hard-Iron-Only, Limited-Tilt, and
Accelerometer. These are briefly discussed below and in more detail in Section 5.
Full Range – recommended calibration method when ≥45° of tilt is possible.
2D – recommended when the available tilt range is limited to ≤5 °.
Hard Iron Only – serves as a hard-iron recalibration to a prior calibration. If the
hard-iron distortion around the device changes, this procedure can bring the device
back into specification more quickly than other methods.
Limited Tilt Range – recommended calibration method when >5° of tilt calibration
is available, but tilt is restricted to <45°. (i.e. full range calibration is not possible.)
Accelerometer – The user should select this when accelerometer calibration will be
performed. Accelerometer calibration is recommended every 6 to 12 months to
compensate for bias drift in the accelerometer. The TRAX can also be returned to
PNI for accelerometer calibration.
Number of Points
This establishes how many samples will be taken during the calibration. The minimum and
recommended number of samples depends on the calibration method, and is summarized in
The following subsections provide instructions for performing a magnetic calibration of a
TRAX system. Several calibration mode options exist, as summarized in Table 5-1. To meet
the accuracy specification, the number of samples should be the “Minimum Recommended”
value, or greater. Calibration may be performed using TRAX Studio or using the PNI binary
protocol, and up to 8 sets of magnetic calibration coefficients may be saved. The
recommended calibration patterns described in the following sub-sections provide a good
distribution of sample points. Also, PNI recommends the location of the TRAX remain fairly
constant while only the orientation is changed.
Table 5-1. The maximum number of samples is 18.
Mag Coefficient Set & Accel Coefficient Set
At any one time, the TRAX will use one set of magnetic calibration coefficients and
one set of accelerometer calibration coefficients. The magnetic coefficients
compensate for measured magnetic distortions in the host system as determined
during a magnetic calibration. The accelerometer coefficients compensate for bias
and offset of the accelerometers, as determined during an accelerometer calibration.