PNI MicroMag - Manual (Page 13)

MicroMag User Manual – March 2010 Page 13 of 23
4 Set-Up & Interface Lines
4.1 PCB Orientation and Output Polarities
Both the MicroMag2-on-Carrier and MicroMag3 have an arrow printed on the PCB
indicating the “reference direction” for the module, while the MicroMag2’s reference
direction is shown in Figure 3-4. The sensors on the MicroMag modules are arranged in
a south-west-down (SWD) coordinate system. The reference direction is parallel to the
x-axis sensor, such that when the MicroMag is pointing directly magnetic south (in the
absence of any other magnetic field) the x-axis reading of the module will be maximized
and the y-axis will be zero. Likewise, when the MicroMag module is pointing directly
west the y-axis reading of the module will be maximized and the x-axis reading will be
zero. For the MicroMag3, the z-axis reading will depend on the dip angle or inclination
at the given location (which is related to latitude). At the geomagnetic equator, where
Earth’s magnetic field is horizontal, the z-axis reading will be zero when flat and at its
maximum when the module is pointed down such that the top of the module faces
magnetic north.
Note that if the MicroMag is used with the PNI CommBoard, the coordinate system is
changed in software to be north-east-down (NED).
4.2 Pin/Pad Connections
The pin and pad numbers for the MicroMag modules are identified on their
respective mechanical drawings, as given in Section 3.3. The connections to be made
the various pins and pads are given below in Table 4-1. The MicroMag2-on-Carrier and
MicroMag3 have similar pin-outs, while the pad connections for the MicroMag2 are
different and include some additional lines. Descriptions of the functions of the various
connections is provided in Section 4.3.