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


Low Frequency Vibration

Low Frequency Vibration

Low Frequency Vibration

This machine has 3 rotating assembles that run at 13.6 Hz, 17 Hz and 19.7 Hz. I am seeing a very strong 3.4 Hz signal which translates into a very large displacement. I can't figure out the source. It only exists when the machine is running other nearby operations don't contribute. The closest thing I found is a bearing FTF at 5.5 Hz.

I'm at a loss, any ideas?

RE: Low Frequency Vibration

17 - 13.6 = 3.4 beat frequency.

RE: Low Frequency Vibration

If my addition is correct you may be getting a beat frequency at 17-13.6 = 3.4 hz.

RE: Low Frequency Vibration

Thanks. I thought that too and forgot to mention it. However, my understanding is that beat frequencies won't be present in structural measurements. The data is from accels. There actually has to be a forcing to get a response.

We also have bellow actuators in the system. they have a natural freq near 3Hz. Still, a forcing frequency near that freq would be necessary to excite.

Another clue; we tested this same exact machine on the same test stand in May. responses are consistent with the exception of this 3.4Hz.

Any other thoughts?

RE: Low Frequency Vibration

"my understanding is that beat frequencies won't be present in structural measurements".

Why would you think that?

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! Already a Member? Login


White Paper – Data Security and Know-How Protection
Our data is constantly exposed to the danger of being intercepted or stolen as it wends its way over global data networks. Data security measures and measures for protecting intellectual property should not, however, first be implemented when data is exchanged – companies must lay the foundation for these measures within their own organization. Download Now
White Paper – Collaboration in the PLM Context
The influence exerted by the Internet of Things (IoT) means that there is a steadily growing need for collaboration in industry. Partners from new industries and areas of application need to be integrated in cross-company business processes to ensure that the lifecycle of smart, connected products can be managed from end to end. Download Now
White Paper – The Challenges of PLM Collaboration
There is cross-company collaboration - and then there is cross-company collaboration. Large-scale corporations and joint ventures need different mechanisms to protect intellectual property from those required for communication between different company locations with heterogeneous IT landscapes. 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