Software tool for noise/vibration/resonance

[vger]

I came across this program that some of you might find a use for. It's a very nice software Oscope/FFT analyzer that uses the sound card as input.

The price can't be beat... FREE

VA - Visual Analyser 4.0 for Windows XP/2000/NT/ME/98/95

You can use a small microphone element as a vibration pickup if you cover the microphone so it doesn't get much/any sound into it. Just hold the covered microphone against the part that is vibrating. You can see gear mesh frequencies, stepper resonance... etc.

There is a "Peak hold" check box in the spectrum settings so you can attach the pickup to a part, then bump/thump the part and find it's natural resonance.

Uncheck the "Log Y axis" to put the grass at the bottom. The thing is even calibratable if you have a standard to calibrate it with.
Steve

[mike_Kilroy]

hey thanks Viper!

I recently helped a customer in CA diagnose a motor winding that was shorting out when motor got hot with this approach! I had the customer turn on their windows sound recorder, hold laptop against motor case while moving motor so we got the sound it was making (was too hi a freq to come thru his cell phone to me). He emailed it to me, I stuck it in my spectrum analyzer and found a nice solid 1.5khz spike at 1x/rev rate; told me the motor winding was partially shorting out when voltage on that phase got to peak of the sine - causing the motor inductance to reduce enough to cause the servo drive's current loop to go unstable and oscillate at 1.5khz!

Poor customer was down nearly 6 months while everyone and their brother had tried to find the problem until this.

So thanks for the free program I can share with others!

[vger]

Mike,

Great story I run into some really strange ones every once in a while. I was doing vibration analysis rounds at a steel mill for a while and lugging the instrument (laptop) around while crawling over rolling mill stands just wasn't feasable. I used a small hard drive based MP3 player recorder (set to record in .WAV format) with an IRD 544 as a pickup, and just recorded about 30 seconds of each point. After recording 136 points, I could play them back into the analyzer and save the spectrums. Worked pretty well.

I have 3 clamp type current probes that have BNC connectors for connection to instruments. It's amazing what you can find looking at FFT spectrums of 3 phase motor currents. Especially when the motor is being driven by a VFD.

A customer called me one morning saying "One of our cooling tower fans just went out of balance over night". They shut them down at night when there is no demand. 24 ft dia fan had the top of the tower in motion about 1/4" at 180 RPM (3 Hz). The fan blades were hollow fiberglass construction and have drain holes at the blade tips. I figured the heavy blade had clogged drain holes so out came the drill and drill bit to clear them out. The drill bit came out covered with blood, bits of bone, and feathers !!! A bird had gotten into the shank of the fan blade at the hub and when they turned the fan on in the morning, the bird took a ride to the tip of the blade.

Have a good one

[mike_Kilroy]

Vger, cool beans! yep, lots of info in the raw data! I enjoyed your first 2 stories, then most of 3rd b4 I got the bird! sounds like some of the problems they have with windmills. thanks again for the program link - it seems on the surface better suited to our use than 2 separate programs I have been using. i will sure give it a workout!

[vger]

Mike,

The software I use on the job comes from Sound Technologies called "SpectraLAB". I have a much older version than the current one but it works great for me. It will let you display the signal calibrated in Volts, G's, Velocity, Displacement, or Db. Waterfall plots, time domain, recording, post processing with filters etc. You can input a response curve to flatten the response of your pickup / microphone / whatever. It will let you capture data and control the analyzer from another program like MS Excel using VB macro's. I don't know what current pricing is, mine is almost 10 years old. The only other software I've been considering is LabView from National Instruments, but I've not been able to justify getting it just yet.

Steve