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# Question regarding DC Accelerometer Experimenter

Hi all,

Consider a DC accelerometer that reads 1g when sitting stationary on top of a table. We have a couple of questions about what it would read in following scenarios (we are trying to replicate a signal in a CAE model that would look like DC accel's signal in testing and would like to make sure that our formulae etc are correct).

- What would a DC accel read in Z (as function of time) if it is allowed to free fall without rotation.

- What would it it read in Z (as function of time) if it is attached to an end of a perfecty simple pendulum (all mass at a point) intially held horizontal with the DC accel attached at the center of mass with Z pointing upward (Z of DC accel is perpendicular to length of pendulum). (see pic below for the second case)

Thank you all! 2 REPLIES 2

# Re: Question regarding DC Accelerometer  Siemens Phenom

Hello MakD,

If the DC Accelerometer is at rest it will see 1G.  Since you have it on a pendulum I would expect it to be somewhere between 1 and 0 and -1 (when upside down at 180 degrees) at 0 Hz.  It would depend on how much the pendulum string constrains the free fall and what angle the accelerometer is at because as it inclines it will not see 1 G but a vector.

Per your formulas the acceleration is probably some form of   Acceleration * cosine(theta) where initially it has cosine(0), at the bottom a cosine(-90) and at end of the swing cosine(-180).  Not sure how much the string constrains it through.

I found some information via google search:

https://en.wikipedia.org/wiki/Accelerometer

https://www.digikey.com/en/articles/techzone/2011/may/using-an-accelerometer-for-inclination-sensing

Maybe others can add responses as well

# Re: Question regarding DC Accelerometer Experimenter

Hi Kevin,