[SOLVED] need clarification about adxl335

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dxtr

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hey everyone , i have an accelerometer adxl335 , i'm trying to figure out how it works
i put it in the table 'not moving' and its gives me :
Xout = 1.447v
Yout = 1.525v
Zout = 1.803v
i still remember a little about physics and i know if an object is not moving it acceleration is 0 m/s² ( a = dv/dt )
then why it gives me those values ? shouldn't give me 0v at the output ?
i need some clarification please
 

If the sensor is in zero acceleration position, it produces about 1.5 V,
so Xout = 1.447v and Yout = 1.525v are OK.

> <i>i know if an object is not moving it acceleration is 0 m/s²</i>

It is true concerning horizontal axis,
but vertical axis sensor is affected by gravity, i.e. 1g.
Sensitivity is 300mV/g, therefore 1g gives additional 300 mV.
You have 1.803v, it is absolutely normal.
 
dxtr said:
i still remember a little about physics ...
Click to expand...

Apparently the emphasis should be on "little".

Due to the fact the following statement is simply not correct.

dxtr said:
... i know if an object is not moving it acceleration is 0 m/s² ( a = dv/dt )
Click to expand...

The are numerous cases when an object has 0 m/s velocity (not moving) and still under acceleration (≠ 0 m/s²).

A simple analogy:

You toss a ball perfectly straight up into the air.

At some point the ball with come to a complete stop (0 m/s velocity), motionless for a finite period of time, before beginning to fall/move back towards you.

During the balls entire flight it is accelerating due to gravity, approximately 9.8 m/s² towards the earth.

It is in fact this gravitational acceleration which brings the ball to a momentary stop, motionless, during its flight.



BigDog
 
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