Introduction, 2 introduction – PNI RM3000 Sensor Suites User Manual
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RM3000 & RM2000 Sensor Suite User Manual r08
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2 Introduction
Thank you for purchasing PNI Sensor Corporation’s RM2000 or RM3000 Geomagnetic Sensor
Suite (pn 90042 and pn 90043, respectively). The RM2000 is comprised of two Sen-XY
Geomagnetic Sensors (pn 12683) and a 3D MagIC ASIC controller (pn 12927), and this forms
the basis for a 2-axis digital compass. The RM3000 is the same as the RM2000 but adds a Sen-Z
Geomagnetic Sensor (pn 12779), such that compassing measurements are not constricted to the
horizontal plane.
When implementing a 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, and the circuit’s oscillation frequency varies with the strength of the magnetic
field parallel to the sensor. The 3D MagIC’s internal clock measures the circuit’s oscillation
frequency, and the magnetic field strength is derived from this. The 3D MagIC also contains
interface circuitry to communicate with the 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.
Since the Geomagnetic Sensor Suite works in the frequency domain, resolution 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 resolution 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” a
Note:
PNI’s Sen-Z Shield is available as an option to provide mechanical protection to the Sen-Z sensor
since the solder joint that attaches the Sen-
Z to the user’s PCB may break if the Sen-Z is impacted. The
Sen-Z shield generally should not be required in a well-controlled, high-volume production environment,
but may be advisable for product development and testing or in less-controlled production environments.