EVAL-ADXL325Z Analog Devices Inc, EVAL-ADXL325Z Datasheet - Page 10

• Manufacturer Part Number: EVAL-ADXL325Z
• Description: Accelerometer Eval. Board
• Manufacturer: Analog Devices Inc
• Series: iMEMS®r

Specifications of EVAL-ADXL325Z

• Silicon Manufacturer: Analog Devices
• Application Sub Type: Accelerometer - Three-Axis
• Kit Application Type: Sensing - Motion / Vibration / Shock
• Silicon Core Number: ADXL325
• Sensor Type: Accelerometer, 3 Axis
• Sensing Range: ±6g
• Interface: Analog
• Sensitivity: 174mV/g
• Voltage - Supply: 1.8 V ~ 3.6 V
• Embedded: *
• Utilized Ic / Part: ADXL325
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

ADXL325
THEORY OF OPERATION
The ADXL325 is a complete 3-axis acceleration measurement
system. The ADXL325 has a measurement range of ±5 g
minimum. It contains a polysilicon surface micromachined
sensor and signal conditioning circuitry to implement an open-
loop acceleration measurement architecture. The output signals
are analog voltages that are proportional to acceleration. The
accelerometer can measure the static acceleration of gravity in
tilt-sensing applications, as well as dynamic acceleration, resulting
from motion, shock, or vibration.
The sensor is a polysilicon surface micromachined structure
built on top of a silicon wafer. Polysilicon springs suspend the
structure over the surface of the wafer and provide a resistance
against acceleration forces. Deflection of the structure is measured
using a differential capacitor that consists of independent fixed
plates and plates attached to the moving mass. The fixed plates
are driven by 180° out-of-phase square waves. Acceleration deflects
the moving mass and unbalances the differential capacitor resulting
in a sensor output whose amplitude is proportional to acceleration.
Phase-sensitive demodulation techniques are then used to determine
the magnitude and direction of the acceleration.
The demodulator output is amplified and brought off-chip through
a 32 kΩ resistor. The user then sets the signal bandwidth of the
device by adding a capacitor. This filtering improves measurement
resolution and helps prevent aliasing.
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MECHANICAL SENSOR
The ADXL325 uses a single structure for sensing the X, Y, and Z axes.
As a result, the three axes sense directions are highly orthogonal
with little cross-axis sensitivity. Mechanical misalignment of the
sensor die to the package is the chief source of cross-axis sensitivity.
Mechanical misalignment can, of course, be calibrated out at
the system level.
PERFORMANCE
Rather than using additional temperature compensation circuitry,
innovative design techniques ensure that high performance is
built-in to the ADXL325. As a result, there is neither quantization
error nor nonmonotonic behavior, and temperature hysteresis is
very low (typically <3 mg over the −25°C to +70°C temperature
range).