ADXL213 查看數據表（PDF） - Analog Devices

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ADXL213

Low Cost ±1.2 g Dual Axis Accelerometer

Analog Devices 

ADXL213

Peak-to-peak noise values give the best estimate of the

uncertainty in a single measurement. Table 6 gives the typical

noise output of the ADXL213 for various CX and CY values.

Table 6. Filter Capacitor Selection (CX, CY)

CX, CY RMS Noise Peak-to-Peak Noise

Bandwidth(Hz) (µF) (mg)

Estimate (mg)

10

0.47 0.64

3.8

50

0.1 1.4

8.6

100

0.047 2

12

500

0.01 4.5

27.2

USING THE ADXL213 WITH OPERATING

VOLTAGES OTHER THAN 5 V

The ADXL213 is tested and specified at VS = 5 V; however, it can

be powered with VS as low as 3 V or as high as 6 V. Some perfor-

mance parameters will change as the supply voltage is varied.

The ADXL213 output varies proportionally to supply voltage. At

VS = 3 V, the output sensitivity is typically 28%/g.

The zero g bias output is ratiometric, so the zero g output is

nominally equal to 50% at all supply voltages.

The output noise also varies with supply voltage. At VS = 3 V, the

noise density is typically 200 µg/√Hz.

Self-test response in g is roughly proportional to the square of

the supply voltage. So at VS = 3 V, the self-test response is

equivalent to approximately 270 mg (typical), or 8%.

The supply current decreases as the supply voltage decreases.

Typical current consumption at VDD = 3 V is 450 µA.

USING THE ADXL213 AS A DUAL-AXIS TILT

SENSOR

One of the most popular applications of the ADXL213 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, 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 accelera-

tion 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 both its X and Y axes 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. 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

calculated as follows:

PITCH = ASIN(AX/1 g)

ROLL = ASIN(AY/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 10 of 12

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