PNI RM3100 Sensor Suite - Manual (Page 19)

PNI Sensor Corporation Doc 1017252 r03
RM3100 & RM2100 Sensor Suite User Manual Page 18 of 45
Figure 4-4: RM3100 North-East-Down (NED) Sensor Layout
If the Sen-Z-f sensor coil is flipped to the bottom of the board such that the polarity
indicator still points back or the curved portion of the sensor still points forward, then to
retain NED the Sen-Z-f’s ZDRVN and ZDRVP pads should be as shown above, except
on the bottom of the board. As the pads on the Sen-Z-f have switched positions, the
connections to the Sen-Z-f sensor will be reversed.
4.2.2 Local Magnetic Field Considerations
Because the RM3100 sensor measure magnetic field, it is important to consider what
items in the vicinity of the sensors can affect the sensor readings. Note that magnetic
field drops off as (1/distance)
3
. Specific issues to consider include:
The sensors have a specified linear regime of 200 T. (Earth’s field is ~50 T.)
To ensure the sensors operate in their linear regime, do not place the sensors close
to large electric currents, large masses of ferrous material, or devices
incorporating permanent magnets, such as speakers and electric motors.
Locate the sensor coils away from changing magnetic fields. If this is not
possible, but the local magnetic field is known to have multiple states, try to take
readings only when the field is in a known state. For instance, if a motor runs part
of the time, take readings only when the motor is in a known state.
If you are uncertain about the effect a specific component may have on the
system, the RM3100 Evaluation Board can be used to help ascertain this. Place
the RM3100 Evaluation Board on a firm surface and gradually bring the
component in question close to the board, then note when the magnetic field starts
to change. If the component cannot be moved, then gradually move the RM3100
Evaluation Board towards the component, carefully ensuring the orientation of the
board remains constant while doing this.