Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here


Calcn. of Displacement, Velocity & acceleration

Calcn. of Displacement, Velocity & acceleration

Calcn. of Displacement, Velocity & acceleration

I just want to know, if acceleration displayed on vibration analyzer can be directly divided by angular velocity of the shaft in order to obtain the value of veloity(mm/sec)and similarly for displacement(velocity/angular velocity of the shaft).

RE: Calcn. of Displacement, Velocity & acceleration

Yes, but only at a single frequency this does not hold for a complex wave. For a sine wave, the conversions in metric units:

V= pi*f*D

where V is velocity in meters/second

and D is displacement in meters pk-pk

and f is the frequency of the sine wave in Hz

I'll leave it to you to convert from meters to mm or microns.

RE: Calcn. of Displacement, Velocity & acceleration

Dear dgallagher,

thanks for the information, but i have a small suggestion to make. Foll. is the formulas displayed in u'r website,
I think wherever 103 is displayed it's 10E+03, which otherwise could be misleading.

But for the rest thank you,


D = Displacement, P-P, Mils.
V = Velocity, 0-P, in/sec.
A = Acceleration, 0-P, g's.

D = 19.10 x 103 x (V/CPM)
D = 70.4 x 106 x (A/CPM2)

V = 52.36 x 10-6 x D x CPM
V = 3.87 x 103 x (A/CPM)

A = 14.2 x 10-9 x D x CPM2
A = 0.27 x 10-3 x V x CPM

RE: Calcn. of Displacement, Velocity & acceleration

The original question involved converting between acceleration, velocity, and displacement based upon the shaft angular velocity (rpm or rpm/60).

The first response correctly pointed out that any such conversion only holds for a single frequency (the conversion is frequency-dependent).

Subsequent formula's would be correct by substituting f=shaft angular velocity IF AND ONLY IF the acceleration is due soley to vibration at 1x running speed.   Such vibration is common, but sometimes the predominant vibration may be 2x, 3x running speed etc (for misalignment, blade pass, gear mesh etc)or even a non-syncronous multiple of running speed (for bearing problem).

RE: Calcn. of Displacement, Velocity & acceleration

kashyap - thanks for pointing out the typo in the formula - must not have translated properly when it was imported into the website.

RE: Calcn. of Displacement, Velocity & acceleration

Judging from the questions you've been asking,  you might want to invest in a text on the subject.

RE: Calcn. of Displacement, Velocity & acceleration

Dear Rob,

  good observation & analysis,

keep - it - up!!!!!!!!!!   



Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


eBook - Mastering Tolerances for Machined Parts
When making CNC machined parts, mastering tolerances can be challenging. Are general tolerances good enough? When does it make sense to call out for tighter tolerances? Do you need a better understanding of fits, datums, or GD&T? Learn about these topics and more in Xometry's new e-book. Download Now
eBook – How to Choose the Correct Corrosion Testing Method
When designing a metal component, engineers have to consider how susceptible certain alloys are to corrosion in the final product’s operating environment. In a recent study by NACE (National Association of Corrosion Engineers), it was estimated that the direct and indirect costs of corrosion in the United States is approximately 6.2% of the GDP. In 2016, that cost exceeded $1 trillion dollars for the first time. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close