ADXL212 Просмотр технического описания (PDF) - Analog Devices
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ADXL212 Datasheet PDF : 12 Pages
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USING THE ADXL212 WITH OPERATING
VOLTAGES OTHER THAN 5 V
The ADXL212 is tested and specified at VS = 5 V; however, it
can be powered with VS as low as 3 V or as high as 5.25 V. Some
performance parameters change as the supply voltage varies.
The ADXL212 sensitivity varies proportionally to supply
voltage. At VS = 3 V, the sensitivity is typically 7.5%/g.
The zero g bias output is ratiometric to supply voltage;
therefore, the zero g output is nominally equal to 50% at all
supply voltages.
Self test response in g is roughly proportional to the square of
the supply voltage. Therefore, at VS = 3 V, the self test response
is equivalent to approximately 270 mg (typical), or 6%.
The supply current decreases as the supply voltage decreases.
Typical current consumption at VDD = 3 V is 450 μA.
USING THE ADXL212 AS A DUAL AXIS TILT
SENSOR
A common application of the ADXL212 is tilt measurement. An
accelerometer uses the force of gravity as an input vector to deter-
mine its orientation in space.
ADXL212
An accelerometer is most sensitive to tilt when its sensitive axis
is perpendicular to the force of gravity, that is, parallel to the
surface of the earth. At this orientation, its response to changes
in tilt is highest: its output changes nearly 17.5 mg per degree of
tilt. When the accelerometer is oriented on axis to gravity, that
is, near its +1 g or –1 g reading, the change in output acceleration
per degree of tilt is negligible. At 45°, its output changes by
12.2 mg per degree.
Dual Axis Tilt Sensor: Converting Acceleration to Tilt
When the accelerometer is oriented with both its x-axis and
y-axis parallel to the surface of the earth (reading approximately
0 g), it can be used as a dual axis tilt sensor with a roll axis and a
pitch axis. The output tilt in degrees is calculated as follows:
Pitch = ASIN(AX/1 g)
Roll = ASIN(AY/1 g)
where AX and AY are accelerations in g, ranging from −1 g to +1 g.
Be sure to account for overranges. It is possible for the
accelerometers to output a signal greater than ±1 g due to
vibration, shock, or other accelerations.
Rev. 0 | Page 11 of 12
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