Introduction, 2 introduction – PNI RM3100 Evaluation Board User Manual
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PNI Sensor Corporation
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RM3100 Evaluation Board User Manual
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2 Introduction
Thank you for purchasing PNI Sensor Corporation’s RM3100 Evaluation Board, pn 13606. The
RM3100 Evaluation Board is a plug-and-play module (PCA) version of PNI’s RM3100
Geomagnetic Sensor, principally intended for quickly evaluating and prototyping PNI’s
magnetic sensor technology. The primary components of the RM3100 Evaluation Board are two
Sen-XY-f sensor coils, one Sen-Z-f sensor coil, and PNI’s MagI2C ASIC controller. It also
incorporates resistors, capacitors, and connectors, all mounted on a PCB, to provide a complete
magnetic field sensing module. The RM3100 Evaluation Board incorporates both I
2
C and SPI
interfaces for system design flexibility.
PNI’s geomagnetic sensor technology provides high resolution, low power consumption, large
signal noise immunity, a large dynamic range, and high sampling rates. Measurements are stable
over temperature and inherently free from offset drift. The RM3100 Evaluation Board features
both continuous measurement mode and single measurement polling, an alarm feature for
monitoring magnetic field strength, software-configurable resolution and sample rate, and the
ability to operate one, two, or all three PNI sensor coils. These advantages make PNI’s RM3100
Evaluation Board not only the choice for prototyping high volume solutions, but also for lower
volume applications that require a complete solution.
Each sensor coil of the RM3100 module serves as the inductive element in a simple LR
relaxation oscillation circuit, where the coil’s effective inductance is proportional to the magnetic
field parallel to the sensor axis. The LR circuit is driven by the MagI2C ASIC and the MagI2C’s
internal clock is used to measure the circuit’s oscillation frequency, and hence the magnetic field.
Since the RM3100 works in the frequency domain, resolution and noise are established cleanly
by the number of MagI2C internal clock counts (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’s performance simply cannot be matched.
Also, the output from the MagI2C 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 PNI’s geomagnetic sensor 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