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Is there a general range for the oscillation of the internal structure in common MEMS gyroscopes and accelerometers?

I'm considering the possibility of damaging MEMS sensors via externally introduced vibrations, ideally through external stimulation at the internal resonant frequency. However, I haven't been able to find much information about the actual internal structure's resonant frequencies.

I'd assume it's fairly high, considering the scale of the features, but I can only really guess.

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  • \$\begingroup\$ these things are small, but also quite light. If I remember correctly you'd expect something within the kHz range. \$\endgroup\$ – Vladimir Cravero Nov 9 '15 at 20:48
  • \$\begingroup\$ @VladimirCravero - That was my assumption, but then I thought about the feature size, and the fact that you can buy MEMS oscillators that go up to the gigahertz range, and I re-evaluated. My current guess is they work in the megahertz range. Making something that small oscillate at a few khz would be hard. \$\endgroup\$ – Connor Wolf Nov 9 '15 at 21:13
  • \$\begingroup\$ Can you provide some source on this MHz MEMS oscillators? Again, small and light. Density is constant so what really counts is the aspect ratio of the components. \$\endgroup\$ – Vladimir Cravero Nov 9 '15 at 21:19
  • \$\begingroup\$ I googled 'mems gyroscope frequency' and was quite entertained for the evening reading the pdfs on the first page. You might try the same. Mr. Fluff's link, answer below, was one of them. \$\endgroup\$ – Neil_UK Nov 9 '15 at 21:27
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MEMS accelerometers have a relatively high resonant frequency- tens of kHz. For example, here is the datasheet for the classic (aka obsolete) ADXL150, which has a resonant frequency of 24kHz typically.

enter image description here

The precision navigation-grade ones (non-MEMS) have a relatively low resonant frequency- more like 1kHz.

Sensitivity is directly related to resonant frequency (the square root of the ratio of spring constant to mass is the angular frequency) so you can expect some consistency in the resonant frequencies of the structures of different designs. They normally have some kind of end stops to prevent damage in case the fundamental frequency gets excited with power off or whatever.

I believe they're almost all force rebalancing types these days, so the mechanical resonance should be greatly damped when they are in normal operation.

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  • \$\begingroup\$ "High" frequency is 30 KHz? O.o. I've been reading about bulk-acoustic-wave gyros, and those suckers run at ~10 MHz! \$\endgroup\$ – Connor Wolf Nov 9 '15 at 22:24
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    \$\begingroup\$ Interesting enough the ADXL150 is a capacitive accelerometer. If it is a typical one, then the thesis I looked at is wrong by an order of magnitude or so. \$\endgroup\$ – Fizz Nov 9 '15 at 22:29
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I'm considering the possibility of damaging MEMS sensors via externally introduced vibrations

Every MEMs oscillator I've come across can survive 10,000g in shock and are far less susceptible than xtals. Read this for example. We could never ever hope to use xtals on our spinning (10,000 rpm to 50,000 rpm) telemetry units but now we are introducing MEMs oscillators cautiously. We're using Silicon labs devices and they have been tested to survive 10,000 g. See this: -

enter image description here

They still work at this level. Is this as high as the shock levels you might induce? The internal resonant frequency will be "stimulated" by external shock so my gut feeling is that unless you are doing something profoundly mechanically "crazy" you won't have a problem.

This answer is only for the oscillator modules. I can't vouch for other mems sensors because I've not investigated them.

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    \$\begingroup\$ The key thing is I'm not looking at pure shock stimulus, but destructive resonance. Basically, I want to possibly blast a MEMS device with ultrasonics (or something else) at it's internal resonance, and see if I can crash the oscillating mass that way. \$\endgroup\$ – Connor Wolf Nov 9 '15 at 21:50
  • \$\begingroup\$ Alternatively, rendering the output values from the MEMS device nonsensical or invalid would also be acceptable. \$\endgroup\$ – Connor Wolf Nov 9 '15 at 21:51
  • \$\begingroup\$ I'm interested in what you find out when u do tests if you can release the info. \$\endgroup\$ – Andy aka Nov 9 '15 at 22:31
  • \$\begingroup\$ If I can release it, I will. I'll have to talk to my boss. \$\endgroup\$ – Connor Wolf Nov 9 '15 at 23:04
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According to this thesis the most common type of accelerometer used in MEMS is the capacitive one, and it has a natural/resonant frequency of "a few kHz".

The info that capacitive MEMS accelerometers are the most common ones also appears in here. So if the aforementioned thesis is wrong with respect to the frequency (which it might be given Spehro Pefhany's answer), you could at least survey some capacitive MEMS datasheets and derive your own range/statistics. Looking at this paper at least some academic ones have indeed a resonant frequency of only a couple of kHz. As another datapoint the datasheet of ADXL105 gives a min of 13kHz, typical 18kHz, and no maximum stated. You may not be so lucky with manufacturers other than AD; I've looks through a few of ST's MEMS accelerometers but they don't seem to give this data [resonant frequency] for any of them. I suspect the reason is that for [MEMS or otherwise] accelerometers the resonant frequency isn't important enough to tell the users, because they can only be used well below that.

enter image description here

Moving to gyros, according to this book there are three common types of MEMS gyros: tuning fork, vibrating wheel, and wine-glass resonators. So you could apply the same methodology to each those. For the vibrating MEMS gyros in general, this paper gives the resonant frequency as 10 kHz to 30 kHz as the most common range. Vibrating gyros are actually designed to vibrate at their natural/resonant frequency. The paper has a graph with both academic and industry devices; I suppose you're only interested in the latter, so you could filter out the graph's data accordingly.

enter image description here

Whether you'd be able to break any of these [accelerometers or gyros] just by externally forced resonance depends obviously on the amplitude of the external vibration as well. Unfortunately determining what amplitude they'd survive at their resonant frequency isn't so easy from datasheets. For accelerometers, you can certainly find the max g they can take, but this for non-repetitive motion/stress; e.g. for LIS3DSH this absolute limit is given as 10000g is for 0.1ms max, 3000g for 0.5ms. The paper I've taken the above graph from says their gyro could handle 1000g continuous external vibration below its resonant frequency [which was 100kHz], and in fact measure robustly in these conditions with error under 0.003°/s/g, but also says a commercial MEMS gyro had an error 1000 times higher, but they don't say at what max g they tested the commercial one.

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