PNI SENtral - Manual (Page 11)

PNI Sensor Corporation Doc #1018049 R03
SENtral Technical Data Sheet Page 10
3.3 Sensor Layout
SENtral provides for considerable flexibility in sensor orientation and layout, but there are
some basic requirements, as given below.

All three axes of a sensor must be orthogonal to each other. This is by-design for
most accelerometers, gyroscopes, and magnetometers.
 A sensor’s X axis and Y axis should act parallel to the primary plane of the
motherboard. A sensor’s Z axis should act perpendicular to the primary plane.

Either a sensor’s X axis or Y axis should align parallel to the line-of-sight of the
motion-tracking device.

It is NOT necessary that the gyroscope, accelerometer, and magnetometer have their
same-axis sensors (i.e. all X-axis sensors) point in the same direction, since sensor
orientation is configured when running the SENtral Configuration Tool and stored in
the SENtral Configuration File.
Assuming the Orientation Matrix is properly input in the SENtral Configuration Tool,
SENtral will output data conforming to a North-East-Down (NED) convention. To convert
to East-North-Up (ENU) see Appendix II – Converting Quaternions.
In addition to the requirements listed above, other recommendations regarding sensor layout
are given below. These represent good practices, but are not mandatory.

Accelerometer
o Locate the accelerometer near the expected center of rotation of the device to
minimize rotational accelerations being interpreted as linear accelerations.

Magnetometer
o Locate the magnetometer >1 cm away from magnetic sources (hard-iron), such as
speaker magnets or known magnetized metals. If uncertain about whether a
component is a magnetic source, check it with a Gauss meter if possible.
o For non-magnetic components, try to avoid placing wireless antenna, power
capacitors, inductors, ferrite beads, and components using ferromagnetic materials
(Fe, Co, Ni) within 1 cm of the magnetometer. Examples of components in a cell
phone which typically contain ferromagnetic materials are the memory card slot,
battery, frame, electrical and magnetic noise shields, connectors, and hinges.
o Materials that are magnetically transparent, and thus relatively safe, include
aluminum, gold, titanium, copper, brass, and magnesium. Most stainless steel
alloys have relatively weak magnetic properties and are not as safe as those just
listed, but don’t need as much attention as ferromagnetic materials.
o Locate high-frequency signal lines away from the magnetometer.
o Locate power lines away from the magnetometer, per the table below.