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    Recording vibrations with an accelerometer

    Hi everyone,

    I'm looking to record vibrations of machines in the frequency range between 0 - ca. 2 kHz with an accelerometer (amplitudes fewer than 4g). According to Shannon-Nyquist theorem I should aim for a sampling frequency of around 4 to 5 kHz.

    After making a survey of commercially available accelerometers from Digikey, I noticed that sampling rates are rarely mentioned in accelerometer datasheets. For example the LSM303 makes mention of SPI and I2C data rates, but doesn't mention the maximum sampling frequency anywhere in the datasheet. It's not mentioned in the characteristic data tables either.

    Am I perhaps looking at the wrong parameter? Or are there other reasons why maximum sampling frequency isn't mentioned in the performance characteristics?

    If anyone has experience with specific accelerometers for this purpose and can recommend some, I'd be very grateful!

    I read about recording vibrations using piezo discs, why is that better or worse than accelerometers for this application?

    •   Alt9th December 2016, 16:43

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    Re: Recording vibrations with an accelerometer

    Maximum accelerometer output data rate is written in the datasheet, it's 800 Hz.

    Most MEMS accelerometers are using AC bridges with demodulator and have respectively low cut off frequencies. I don't know if there's any with 2 kHz bandwidth.


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    Re: Recording vibrations with an accelerometer

    Quote Originally Posted by FvM View Post
    Maximum accelerometer output data rate is written in the datasheet, it's 800 Hz. Most MEMS accelerometers are using AC bridges with demodulator and have respectively low cut off frequencies. I don't know if there's any with 2 kHz bandwidth.
    Which other solutions would you suggest to measure these vibrations, if accelerometers are out of range?



    •   Alt9th December 2016, 18:09

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    Re: Recording vibrations with an accelerometer

    I see that Analog has some MEMS accelerometers with kHz bandwidth and is recently promoting ADXL35x series (1 kHz bandwidth) for machine health monitoring. In so far they may be used. Personally I'm used to piezo transducers since long.


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    Re: Recording vibrations with an accelerometer

    Thanks for the recommendation, FvM, I've looked into piezo transducers as an alternative to accelerometers, and they seem very promising, at least on paper. I've tested a few I had laying around, but unfortunately the performance seems to very greatly. None of them have any type numbers on them, which makes it difficult to replicate results.

    Can you recommend type numbers or manufacturers of piezo transducers you have good experiences with? I have found Cui Inc. discs being widely recommended, so you share that experience?



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    Re: Recording vibrations with an accelerometer

    My customers are e.g. using PI piezoelectric components https://www.physikinstrumente.com/en...ic-components/


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    •   Alt19th December 2016, 09:20

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  7. #7
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    Re: Recording vibrations with an accelerometer

    Quote Originally Posted by FvM View Post
    My customers are e.g. using PI piezoelectric components https://www.physikinstrumente.com/en...ic-components/
    They seem to have an impressive inventory, I'll see if I can get some samples from them. Thanks so much for your recommendation!



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