Distance by Accelerometer?

[Faizan Jawaid]

accelerometer distance

I want to know through what expression i will be able to calculate the distance D. The body moves from rest i.e Initial Velocity=0, and moves with a constant acceleration from time t0 to t1. Then from t1 to t2 body moves with a constant velocity.

Regards.

 

[AVIANO]

accelerometer calculate distance

D=Vi.t+1/2.a.t.t

 

[Kral]

distance from accelerometer

Faizan Jawaid,
The expression given by Aviano is correct, of course.
.
However, I'm interpreting your question to be how to calculate the distance from an accelerometer output. The expression for distance as a function of acceeration is d = ∫∫a dt. In other words, you need to integrate the accelerometer output twice. This expression works regardless of whether the velocity is constant (zero acceleration) for a period of time.
.
There are practical problems in using this approach. The op amps used as integrators will have drift due to offset voltage, offset current and bias current. The accelerometer will have an output bias that must be compensated for.
Regards,
Kral

 

[Faizan Jawaid]

accelerometer distance calculatioin

Thanks you both. Actually i wanna use 'ADXL' accelerometer to calculate the distance. Do u think it can be done? i don't need a highly accurate system.

 

[Kral]

accelerometer constant velocity

Yes, you can use this accelerometer, but you must head the cautions regarding offsets. Also, you must make provisions for resetting the integrators befor beginning the distance calculation. This is usually done by shorting the integrator capacitor. You can calibrate the accelerometer by mounting it vertically, and comparing the output with local gravity.
Regards,
Kral