ADXL210AQC-1 Analog Devices Inc, ADXL210AQC-1 Datasheet - Page 9

• Manufacturer Part Number: ADXL210AQC-1
• Description: IC ACCELEROMETER DUAL 14CERPAK
• Manufacturer: Analog Devices Inc

Specifications of ADXL210AQC-1

• Rohs Status: RoHS non-compliant
• Axis: X, Y
• Acceleration Range: ±10g
• Sensitivity: 100mV/g
• Voltage - Supply: 3 V ~ 5.25 V
• Output Type: Analog
• Bandwidth: 6kHz
• Mounting Type: Surface Mount
• Package / Case: 14-CerPak
• Interface: -

REV. B
STRATEGIES FOR USING THE DUTY CYCLE OUTPUT
WITH MICROCONTROLLERS
Application notes outlining various strategies for using the duty
cycle output with low cost microcontrollers are available from
the factory.
USING THE ADXL202/ADXL210 AS A DUAL AXIS TILT
SENSOR
One of the most popular applications of the ADXL202/ADXL210
is tilt measurement. An accelerometer uses the force of gravity
as an input vector to determine orientation of an object in space.
An accelerometer is most sensitive to tilt when its sensitive axis
is perpendicular to the force of gravity, i.e., parallel to the
earth’s surface. At this orientation its sensitivity to changes in
tilt is highest. When the accelerometer is oriented on axis to
gravity, i.e., near its +1 g or –1 g reading, the change in output
acceleration per degree of tilt is negligible. When the accelerom-
eter is perpendicular to gravity, its output will change nearly
17.5 mg per degree of tilt, but at 45 degrees it is changing only
at 12.2 mg per degree and resolution declines. The following
table illustrates the changes in the X and Y axes as the device is
tilted 90 through gravity.
X AXIS
ORIENTATION
TO HORIZON ( ) X OUTPUT ( g )
Figure 14. How the X and Y Axes Respond to Changes in
Tilt
–
–
–
–
–
–
–
–90
–75
–60
–45
–30
–15
15
30
45
60
75
90
0
Y
–1.000
–0.966
–0.866
–0.707
–0.500
–0.259
0.000
0.259
0.500
0.707
0.866
0.966
1.000
X
X OUTPUT
DEGREE OF
TILT (m g )
PER
–0.2
12.2
15.0
16.8
17.5
16.9
15.2
12.4
4.4
8.6
8.9
4.7
0.2
+90
–90
Y OUTPUT ( g ) TILT (m g )
0.000
0.259
0.500
0.707
0.866
0.966
1.000
0.966
0.866
0.707
0.500
0.259
0.000
0
Y OUTPUT ( g )
1 g
DEGREE OF
–12.2
–15.0
–16.8
–17.5
PER
17.5
16.9
15.2
12.4
–4.4
–8.6
8.9
4.7
0.2
–9–
A DUAL AXIS TILT SENSOR: CONVERTING
ACCELERATION TO TILT
When the accelerometer is oriented so both its X and Y axes are
parallel to the earth’s surface it can be used as a two axis tilt
sensor with a roll and a pitch axis. Once the output signal from
the accelerometer has been converted to an acceleration that
varies between –1 g and +1 g, the output tilt in degrees is calcu-
lated as follows:
Be sure to account for overranges. It is possible for the acceler-
ometers to output a signal greater than 1 g due to vibration,
shock or other accelerations.
MEASURING 360 OF TILT
It is possible to measure a full 360 of orientation through grav-
ity by using two accelerometers oriented perpendicular to one
another (see Figure 15). When one sensor is reading a maxi-
mum change in output per degree, the other is at its minimum.
Figure 15. Using a Two-Axis Accelerometer to Measure
360 of Tilt
Y
X
Pitch = ASIN (Ax/1 g)
Roll = ASIN (Ay/1 g)
ADXL202/ADXL210
360 OF TILT
1 g