Vibration Analysis

How inexpensive? How accurate? Is it for comparison or characterization?

I have used a cheap microphone and an acoustic analyzer taped to pump housings, so I could identify specific frequencies and amplitudes. Then I'd compare this to a known good pump's profiles.

If you just need amplitude, use a db meter.

Just depends what you want to do. Have you looked for sound analysis software on the net?

Before you can implement you have to establish a benchmark, so you know the difference of what its supposed to sound like against when there is something wrong.

You state what items you want to test, but you do not tell us what you want to know. If all you want is amplitude of displacement, accelaration or velocity then a simple SKF Vibropen would do. (There are many other manufacturers to choose from for similar instruments). On the other hand if you are wanting a full FFT spectrum analyser then B& K, SKF, Bently, Schenk and many others are available.

First decide exactly what you want to know and how you want to manipulate your results. This will allow you to buy (second hand equipment is cheap) something fit for purpose accompanied by the right software for your needs.

Great information so far. I used to fly the MH-53 and we would have to run vibration tests on certain parts of the fuselage to determine if parts needed to be replaced or if drive shafts needed to be adjusted. Accelerometers (bi and triaxial) were attached to certain parts of the fuselage with cables running to a computer. The output was read on a computer in a frequency in Hz. I am working on a Dornier DO-335 condeptual design and the biggest problem is the aft engine and drive train. I am looking for a inexpensive but reliable vibration analysis setup to test the vibrations in this aft area.

For a quick and dirty (and cheap) picture of magnitudes and frequencies, I would go with lynchlynch's suggestion of a microphone coupled to a digital oscilloscope that has FFT capabilities. You could probably use one of the software oscilloscopes available for computers for this (i.e., oScope in Linux- there are others that work in the other operating system). This will not give you 3-axis data, and I am not sure it would stand up in a court of law, but I have been able to pick out failing bearings, identify the sources of unwanted vibrations (assuming one knows a bit of the specifications of the various contributors), etc., and come up with isolation solutions that work.

or another option ..... pending on how many test you wish to perform ......

Solidworks coupled with Cosmos - motion can give basic information without distroying anything ...

Anthony@alno

www.alnoproductservices.com.au

The Motorola Droid phone has an App that does that.

Here is a link to Analog Devices.They have a relatively inexpensive vibration sensor that is easily interfaced to your computer: ADXL 105 Chip.

Here is an excerpt from the website:

The primary opportunity posed by the low cost and increasingly high performance of these devices is to enable new applications that weren't possible before. Although there is also a potential for replacing other means in existing applications, there is no reason to believe that designers who design or customers who purchase precision instruments will suddenly change to a new technology strictly on the basis of cost, as there are other important considerations in the precision instrumentation business.

However, there is a limitless opportunity to develop new or expanded uses of precision sensors. For example, the new technology may allow designers to instrument full-time monitoring of every machine, motor, pump or compressor that a manufacturer makes. New low cost, precision sensors with their fully signal conditioned output can reduce the cost of each point in a real-time monitoring system from $1000 to under $100. That kind of cost reduction makes feasible new uses for sensors that were not possible before. For example, a manufacturer of industrial equipment can now economically produce a "smart motor", which has high-efficiency drive electronics employing DSP for speed control, and accompany it by a low-cost machine-health conditioning module to increase energy efficiency, improve up time, reduce maintenance cost, and thus lower the end customer's total cost of ownership.

http://www.analog.com/library/analogDialogue/archives/33-06/adxl105/article.html

Good Luck

The iphone has some vibration analysis apps. I don't know how good they are but if you already have an iphone then you won't find any other tool cheaper than purchasing an app.

Same query here. I'm looking for similar equipment for open gear (girth gears) vibration analysis. Need inputs pl

You will need an accelerometer connected to an A/D converter whose output is fed to an FFT program in order to measure the frequencies and harmonics. Be absolutely sure to use an anti-aliasing filter to condition the accel output before going to the A/D.

The best route is to go to used sources to buy a commercially made vibration analyzer.

The Apple iPad has a full spectrum vibration analysis app with external accelerometor's. This is a very inexpensive solution and I think they have several apps to suport balancing, bearing, and gear defect frquency's. If you google iPad vibration analyzer there are several videos on the subject.

If its the vibration app I'm think of, there was a compliant that there was no unit specification on the vibration, allot of charts but no units.

There was something similar with the accelerometer app

I'm not sure which app you were looking at - the one I'm familiar with - VibePro - captures frequency in "Hz/CPM" - it is pretty well marked to show that off. There may be other apps I'm not familiar with.