PNI SeaTRAX - Manual (Page 38)

PNI Sensor Corporation DOC#1018154 r02
SeaTRAX User Manual Page 33
6.7 Graph Tab
The Graph Tab provides a 2-axis (X,Y) plot of the measured field strength. If “w/o User
Cal” graph data is selected, the plot and data provide magnetic field strength measurements
after the FIR taps are applied, but prior to applying the user calibration coefficients. If “with
User Cal” graph data is selected, the plot and data provide data after applying the FIR filter
and the user calibration coefficients. The two sample plots shown above are for the same
360° rotation in the horizontal plane of a SeaTRAX with a battery mounted next to it. For
the “w/o User Cal” plot the data is slightly ellipsoid with an offset of about +4 T in both the
MX and MY direction. The “with User Cal” plot is more clearly a circle and is properly
centered. The plots can be used to visually see hard and soft iron effects within the
environment measured by the SeaTRAX, as well as corrected output after a user calibration
has been performed. Note that if the calibration score is relatively poor, then the “with User
Cal” plot may not be a circle.