Instruction Manual

PNI Sensor Corporation Doc #1016102 r04
RM3000-f & RM2000-f Sensor Suite User Manual Page 5
2 Introduction
Thank you for purchasing PNI Sensor Corporation’s RM2000-f or RM3000-f Geomagnetic
Sensor Suite (pn 90042-f and pn 90043-f, respectively). The RM2000-f is comprised of two
Sen-XY-f geomagnetic sensors and a 3D MagIC ASIC MLF controller, and this forms the basis
for a 2-axis (horizontal) digital compass. The RM3000-f is the same as the RM2000-f but adds a
Sen-Z-f geomagnetic sensor, such that compassing measurements are not constricted to the
horizontal plane.
When implementing an RM3000-f or RM2000-f Geomagnetic Sensor Suite, each geomagnetic
sensor serves as the inductive element in a simple LR relaxation oscillation circuit, with the
sensor’s effective inductance proportional to the magnetic field parallel to the sensor axis. The
LR circuit is driven by the 3D MagIC ASIC. Since the LR circuit’s oscillation frequency varies
with the strength of the magnetic field parallel to the sensor, the 3D MagIC’s internal clock is
used to measure the circuit’s oscillation frequency (cycle counts) and hence the magnetic field.
The 3D MagIC also contains an interface circuitry to communicate with a host microprocessor
on an SPI bus. The 3D MagIC can control and measure up to three PNI geomagnetic sensors,
with each sensor individually selected for measurement and individually configured for
measurement gain (sensitivity).
Since the Geomagnetic Sensor Suite works in the frequency domain, sensitivity and noise are
established cleanly by the number of cycle counts. In comparison, fluxgate and MR technologies
require expensive and complex signal processing to obtain similar sensitivity and noise, and in
many respects the Geomagnetic Sensor Suite’s performance simply cannot be matched. Also,
the output from the 3D MagIC is inherently digital and can be fed directly into a microprocessor,
eliminating the need for signal conditioning or an analog/digital interface between the sensor and
a microprocessor. The simplicity of the Geomagnetic Sensor Suite combined with the lack of
signal conditioning makes it easier and less expensive to implement than alternative fluxgate or
magneto-resistive (MR) technologies.
For more information on PNI’s magneto-inductive sensor technology, see PNI’s whitepaper
“Magneto-Inductive Technology Overview” at http://www.pnicorp.com/technology/papers.