×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

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

Jobs

Vibrating Element Structures

Vibrating Element Structures

Vibrating Element Structures

(OP)
Can anyone recommend a good reference on the design of vibrating element sensors?
Mostly Google comes up with MEMs sensors/energy harvesting devices (but not with the information I am looking for) and I am looking for something that relates to somewhat larger sensors that use piezo drives.

The problem is to know how to get the bit you want to vibrate to vibrate and everything else to not vibrate, or to vibrate at lower amplitude and in some well removed frequencies.

Some sort of guidance is needed on how to design the structure to achieve that.

Any ideas?

JMW
www.ViscoAnalyser.com
 

RE: Vibrating Element Structures

jmw,

   Getting the one part to vibrate and everything else to not vibrate is easy.  Everything else must be a couple of orders of magnitude less flexible (higher natural frequency).  A designer will good engineering skills should be able to pull this off fairly easily.

   Getting the one part to vibrate exactly the way you want will be more challenging, and figuring out where the heck it is while it is vibrating, more challenging still.

   Proximity sensors?

                           JHG

RE: Vibrating Element Structures

(OP)
Thanks Drawoh,
I found a paper on mounting accelerometers which gave some useful advice such as the need to fill cavities with potting compound but nothing that otherwise helps me.

Er, no, not proximity sensors, Im afraid I'm not allowed to say what it is just yet.

JMW
www.ViscoAnalyser.com
 

RE: Vibrating Element Structures

We used this product on our high speed machinery to prevent catastrophic sympathetic vibration of the frames.

I just had a discussion about one of the machines that I worked on in the 90's.  Interest was lost when I mentioned a purchase order or a temp job.  

http://www.iotech.com/vibe.html

If the order of magnitude is fairly high there was a show on TV where they were using a small seismometer to record micro quakes

RE: Vibrating Element Structures

(OP)
Thanks for the link Unclesyd,
by the way, how high is high temperature?
The limit we have begins with the piezos where it depends on the Curie temp but the manufacturers don't seem that enthusiastic about going too high and it looks as if we might comfortably settle at 160-200degC.
Of course, we are not mounting on a circuit board.

JMW
www.ViscoAnalyser.com
 

RE: Vibrating Element Structures

High temperature and high pressure have always been a moving target for me. When I started work our 10,000 psig, with hydrogen and ammonia, process was scary and 300C polymer kelp me on my toes. When I left we had 77,000 psig water and testing equipment pieces to 20,000+ psig.

Just made a call and found out the ones we used are limited to 125C. I don't know if this is manufacturers requirement or just by our procedures. I think manufacturers have gotten more conservative on temperature ratings of equipment.

I would checkout the NASA tech site as I know they have done a lot of work in the area of high temperature transducers.  

RE: Vibrating Element Structures

I vaguely remember that the upper limit on piezo shear type accelerometers is set by the properties of the epoxy they use.

Cheers

Greg Locock

SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.

RE: Vibrating Element Structures

(OP)
Can be.
In one design I found that they had a 200degC piezo with 100degC (or some such silly value) solder and the wrong wiring insulation.
Weakest link stuff.

JMW
www.ViscoAnalyser.com
 

RE: Vibrating Element Structures

GregLocock,
That is probably why we have a low temperature limit based on the current crop of transducers. As you probably remember some Epoxies weren't very good early on, that is the relatively inexpensive ones.

 

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!


Resources