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I want to measure the vibration of a roller coaster cart while it is riding down the tracks. Handheld data loggers with a pin on them won't work. I'd need something I can attach or place inside of the roller coaster track. I am worried that conventional data loggers won't be well suited for this because the acceleration of the cart influences the vibration readings when using an accelerometer. I have found exactly 0 results on Google for "measuring vibration of moving objects"-like queries. I want to measure 3-axis G-force.

Is there anything you could recommend me to use?

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  • $\begingroup$ An accelerometer app on a smartphone as a cheap option , if not a 3 axis accelerometer connected to a Cambell data logger budget permitting... $\endgroup$ – Solar Mike May 19 '17 at 13:57
  • $\begingroup$ PLease clarify: is the problem finding a data logger, or finding a decent vibration sensor? Nearly any sensor can be fed directly to a PC with some National Instruments hardware. $\endgroup$ – Carl Witthoft May 19 '17 at 14:46
  • $\begingroup$ Are you trying to measure the vibration of the track, inside the car or both? $\endgroup$ – DLS3141 May 19 '17 at 15:03
  • $\begingroup$ There are lots of options here, which unfortunately means lots of questions to narrow down the choices. What recording rate are you looking for? A high frequency time history, say, 10,000 samples/sec, or just a rough "overall vibration level" recorded at a much lower frequency like once per second? $\endgroup$ – Daniel K May 20 '17 at 3:16
  • $\begingroup$ The exact problem is how do I measure vibration in a moving object like a rollercoaster vehicle. Because it accelerates and decelerates the G-forces measured by a vibration sensor using an accelerometer are off since they also include the acceleration of the vehicle. This in contrast to a stationary machine which does not move. $\endgroup$ – Zimano May 20 '17 at 9:58
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The exact problem is how do I measure vibration in a moving object like a rollercoaster vehicle. Because it accelerates and decelerates the G-forces measured by a vibration sensor using an accelerometer are off since they also include the acceleration of the vehicle. This in contrast to a stationary machine which does not move

To do this, you do in fact want an accelerometer, and then you want to add to it a thing called a "high pass filter".

The reason this will work is that the "rigid body acceleration" you refer to is at a fairly low frequency compared to the vibration you want to measure. Consider your basic roller coaster ride. Going up the first your accelerometer is going to measure 1g in the vertical direction. Then going down the hill, you measure much less than one g in vertical direction, say 0.2g for a few seconds (this is assuming that your accelerometer always stays in vertical direction and doesn't change with the direction of the car). Then at the bottom of the hill, you are measuring more than 1g, say 2.0g, again for a few seconds. So our signal will have a 1 -> 0.2 -> 2.0 g waveform lasting maybe 5 seconds, or effectively 0.2 Hz. Superimposed on top of that is the vibration you want to measure. That will be at a higher frequency, perhaps 10 - 1000 Hz. So if you apply a high pass filter with a 1 Hz cutoff frequency, you'll get rid of the 0.2 Hz rigid body acceleration and keep the 10 - 1000 Hz vibration. The filtering could be done before the recording is made, or you could just record the whole thing and then filter it out later.

Another entirely different option, would be to use a displacement sensor that measures the distance between the car and the track, which will change very slightly as the car vibrates. These types of sensors can be made with a resolution of better than 0.001", so should be able capture to the vibration of interest.

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  • $\begingroup$ An excedllent answer providing me with a viable solution. I am going to check out this filtering; I've thought about it but didn't know if it would be practical. Thanks! $\endgroup$ – Zimano May 21 '17 at 12:44
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I'm sure there is more than one way to do what you want, but based on what you have posted and my experience measuring vibration in and out of vehicles, this is basically how I would do it:

I used an earlier version of these data recorders from IST to measure the vibration environment inside shipping containers and truck trailers as they travelled around the world.

For this application, I would mount 1 inside the cart using the built in sensors, and a second unit mounted near the tracks, using external accelerometers. Triggering both systems to record at the same time would be tricky, but I would set up optical sensors to trigger both or use one optical sensor to trigger a radio module which would in turn trigger both recorders. They won't be perfectly synced, but probably good enough. I'm sure that the folks at IST would be more than happy to help you with getting this set up.

Another nice thing about IST is that they rent equipment so you don't necessarily have to make a huge investment.

Note: I am not associated with IST in any way aside from being a satisfied customer.

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And a google search for "vibration datalogger" gave : https://www.crystalinstruments.com/coco-90-dynamic-signal-analyzer-and-data-collector/?gclid=CPz8w9KO_NMCFSEW0wodzs4FHQ

As the first result....

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    $\begingroup$ The CoCo 90 is a great device for measuring vibration on equipment using external accelerometers, but it's simply NOT ruggedized enough to survive long mounted inside a vehicle that is subjected to significant vibration levels itself. $\endgroup$ – DLS3141 May 19 '17 at 15:03
  • $\begingroup$ my comment was made about the results available when searching as the OP states they had 0 results... $\endgroup$ – Solar Mike May 19 '17 at 15:08
  • $\begingroup$ OK, that makes sense then. $\endgroup$ – DLS3141 May 19 '17 at 15:09
  • $\begingroup$ Had success with these and they are quite tough : picotech.com/products/data-logger $\endgroup$ – Solar Mike May 19 '17 at 15:13
  • $\begingroup$ Those ARE pretty cool, but I don't see any signal conditioning capability. $\endgroup$ – DLS3141 May 19 '17 at 15:33

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