Wireless Vibration Monitoring 1

[goldfields]

I need to make use of wireless on-line vibration monitoring on blades of a rotating fan. What technologies or techniques are available other than scanning laser vibrometers?

 

[Hatch]

I don't know of any technology to do wireless vibration measurements on a rotating member. It is interesting because any conventional accelerometer or transducer would mostly see centrifugal forces (if it is mounted radially) and would therefore have a mostly sinusoidal accelerations which I assume are not what you are looking for. If it is mounted axially, I would expect some leakage from the radial forces and the same thing would happen.

However, you could mount strain gauges on the fan blades or shaft and monitor the stresses during rotation by use of a transmitter. The stress readings could be calibrated to an equivalent vibration level.

 

[GregLocock]

SPATE might be worth a look.

Stress patterns by thermal emissions.

It's a camera that gives you stress contours. I don't know if it can cope with a rotating target.

SDRC or GenRad used to sell the system.

Cheers

Greg Locock Cheers

Greg Locock

 

You could do something really cheap and nasty by setting up a minidisk recorder to a portable accelerometer power supply. I use a SONY MZ-R30 to record at 44 kHz digitally and I use a PCB 480E09 power supply to power the accelerometer. This will give you about 40 minutes of recording time. Tape everything to the fan shaft and start it recording - start the fan. After the fan is stopped you can play the vibration back into any vibration analyzer which has an aux input connection. The beauty then is that you can analyze at different frequencies under all sorts of conditions.

Good luck

Ron Frend

 

[GregLocock]

That's evil.

Incidentally you shouldn't use a minidisc for analytical work unless you really understand the compression formula they've used, or disabled it somehow. As I remember the algorithm only retains (worst case) 25% of the data!





Cheers

Greg Locock

 

[ronfrend]

Yes you need to be aware of the algorithms used. There is a nice description at

http://hive.me.gu.edu.au/~csand/md/mdpage/minidisc/aes_atrac.html

For the frequencies of fan blades I think you should be OK.

 

[GregLocock]

Sometimes someone posts exactly the right information.

Thanks
Cheers

Greg Locock