ADXL206 Analog Devices, ADXL206 Datasheet - Page 11

• Manufacturer Part Number: ADXL206
• Description: High Temperature iMEMS Accelerometer
• Manufacturer: Analog Devices

USING THE ADXL206 WITH OPERATING VOLTAGES
OTHER THAN 5 V
The ADXL206 is tested and specified at V
can be powered with V
performance parameters change as the supply voltage is varied.
The ADXL206 output is ratiometric; therefore, the output
sensitivity (or scale factor) varies proportionally to the supply
voltage. The zero g bias output is also ratiometric; therefore, the
zero g output is nominally equal to V
The output noise is not ratiometric but is absolute in volts;
therefore, the noise density decreases as the supply voltage
increases.
Self-test response in g is roughly proportional to the square of
the supply voltage. However, when ratiometricity of sensitivity
is factored in with supply voltage, self-test response in volts is
roughly proportional to the cube of the supply voltage. There-
fore, at V
50 mV or about 160 mg.
S
= 3 V, the typical self-test response is approximately
S
as low as 3 V or as high as 6 V. Some
S
/2 at all supply voltages.
S
= 5 V; however, it
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USING THE ADXL206 AS A DUAL-AXIS TILT
SENSOR
One of the most popular applications of the ADXL206 is tilt
measurement. An accelerometer uses the force of gravity as an
input vector to determine the orientation of an object in space.
An accelerometer is most sensitive to tilt when its sensitive axis
is perpendicular to the force of gravity, that is, parallel to the
earth’s surface. At this orientation, the sensitivity of the acceler-
ometer to changes in tilt is highest. When the axis of sensitivity
is parallel to gravity, that is, near its +1 g or −1 g reading, the
change in output acceleration per degree of tilt is negligible.
When the accelerometer is perpendicular to gravity, its output
changes nearly 17.5 mg per degree of tilt. At 45°, its output
changes at only 12.2 mg per degree and resolution declines.
Dual-Axis Tilt Sensor: Converting Acceleration to Tilt
When the accelerometer is oriented so that both its x-axis and
y-axis are parallel to the earth’s surface, it can be used as a 2-axis
tilt sensor with a roll axis and a pitch axis. After the output signal
from the accelerometer is converted to an acceleration that varies
between −1 g and +1 g, the output tilt in degrees is calculated
as follows:
Make sure to account for overranges. It is possible for the
accelerometer to output a signal greater than ±1 g due to
vibration, shock, or other accelerations.
PITCH = arcsin(A
ROLL = arcsin(A
Y
/1 g)
X
/1 g)
ADXL206