Random vibration units

[jimmyjimbob]

I normally input my random vibration units into my controller as g2/Hz. Sadly I have been given a specification quoting an ASD of 1.92m2/s3

Does anyone know how I can convert m2/s3 to g2/Hz.

Thanks

 

[SomptingGuy]

The dimensions are compatible. Is there not just a factor of (9.81)^2 to either multiply or divide by?

- Steve

 

[jimmyjimbob]

Thanks,
I remember doing this ages ago but was not too sure. Thanks for the prompt response I can now run my test today,


Thanks again.

 

[SomptingGuy]

... beware of peak-peak, peak, RMS differences too. Always a killer and best to understand before trusting and using these numbers.

- Steve

 

[jimmyjimbob]

Ahhhh..... Could you explain a bit of what you mean by this to me. I am worried that I miss something that is fundamental and wrong basically.

 

[SomptingGuy]

Sine wave: x=a*cos(2.pi.w.t)

Peak = a
Peak-Peak=2.a
RMS=a/sqrt(2)

If you are using a calibrator, it'll probbaly be set to a dB(RMS) acceleration value. That would be an RMS value divided by a reference RMS value, then logged, etc.

In my days working in this area, I never trusted any piece of vibration measurement equipment that didn't output instantaneous m/s2, which I could then mangle however I chose.

- Steve

 

[jimmyjimbob]

Thanks, I am with you now.... I think.

Your assistance and advice is greatly appreciated. Thanks for your time. This is a great site because you guys put in so much effort to help.

Thanks again.