PDA

View Full Version : [Question(s)] Accelerometer



Dewayne4444
06-11-2009, 12:17 PM
I need to measure vibration of a rotating cylinder but I am not sure of the type of accelerometer to use. It may also be used for other measurements so I don't want a vibration sensor. I need some advice on what frequency and g range would work for vibration.

Adrenalynn
06-11-2009, 12:34 PM
Welcome to the forum!

I suspect we'll be needing more information than that. A 20meter, 12 Ton steel cylinder rotating at 1 rotation per month would have a very different signature than would a 2mm, 3g Delron cylinder rotating at 30,000RPM.

Even with that, we'd be guessing - but at least our guesses will be somewhere in the "educated" realm. ;)

Dewayne4444
06-11-2009, 12:55 PM
Sorry for my vagueness. I am rotating a set of aluminum cylinders with a height of 60 cm. There is an outer cylinder with a radius of 22 cm and an inner cylinder with between 11 and 21 cm depending on the setup. The cylinders are then filled with water and rotated at a max 2000 rpm. The total weight of the rotating part of the instrument is around 450 lbs. I need to measure the vibration for quality purposes but I am not sure of the g forces that would occur during vibration. I would assume that I would need a minimum frequency to cover the rotational speed which would be around 34 Hz. I would guess that 200 Hz would work fine but I am uncertain of the possible vibrational g forces. Maybe 5-10 g.

ScuD
06-11-2009, 01:28 PM
Analog devices has an entire range (http://www.analog.com/en/mems-and-sensors/imems-accelerometers/products/index.html) of accellerometers, some of which might meet your needs.
However, they top off at 2.5kHz bandwidth so I think you'll be pushing them. There might very well be a higher frequency vibration than the 2000rpm rotation.

Is there a way you can just slap on a simple piezo beeper on there and hook up an oscilloscope to get a rough estimate of the frequency without too much expense? (see the mechwars hit sensor for example)

Robert
12-07-2009, 04:43 PM
What sort of interface are you looking for? A simple analog output that you can feed into something, or something like USB?

I have a sample program that reads acceleration in from a Phidget 3 axis accelerometer http://www.phidgets.com/products.php?product_id=1059, ran it through a software highpass filter to get rid of anything under 4 hz, does a FFT to it in order to show the frequency components, and then graphs it. It was pretty reliable up to a few hundred hz. The sensor is a little noisy, but there's a new one coming out shortly that's a lot better.