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bandwidth of USB6008

Hello to All,

 

I am doing vibration analysis with accelerometers connecting with USB-6008.

However, due to the aliasing, I wanna add a low pass filter at the output pin of accelerometers on a expansion board to deal with it, as the spec sheets of the accelerometer recommended.

However, to select the capacitors, I need to choose the bandwidth.

And I am really do not know what is the suitable bandwidth with USB-6008.

If anyone knows, would you please let me know??

Or any suggestions??

 

Thanks,

Best Regards,

SH

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What rate are you sampling at?  You should set the bandwidth to be a little smaller than half of your sample rate.


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I think 1k/s..

It means 1000hz right?? so I need to choose bandwidth 500hz??

 

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I would go a little less, like 400Hz, due to the band reject slope.


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Thanks for the advice!

BTW, 1k / s sampling will be fine??

USB6008 can increase sample rate upto 10k / s..

I think more sampling rate could get better results.

 

 

 

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Ok, what frequencies are you trying to pick up?  If your frequencies are less than your bandwidth, then don't worry about it.  If you are trying to capture 1kHz signals, then I would setup the bandwidth to something like 3kHz and sample at probably the max 10kHz.

 

Let's put it this way.  Set your bandwidth to something slightly higher than the max frequency you are trying to capture.  As an example, I will go with 800Hz max frequency.  So I would go with something like 1kHz for my filter cutoff.  You just don't want to attenuate your max desired frequency.  So now my sample rate needs to be at least twice the cutoff frequency to avoid aliasing.  So I would probably choose 5kHz for my sampling frequency.

 

Notice that there's no true rhyme or reason to my numbers.  Just the rules that your cutoff needs to be slightly higher than you max signal frequency and your sampling rate needs to be at lease 2x your cutoff frequency.


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Ok, what frequencies are you trying to pick up?  If your frequencies are less than your bandwidth, then don't worry about it.  If you are trying to capture 1kHz signals, then I would setup the bandwidth to something like 3kHz and sample at probably the max 10kHz.

 

Let's put it this way.  Set your bandwidth to something slightly higher than the max frequency you are trying to capture.  As an example, I will go with 800Hz max frequency.  So I would go with something like 1kHz for my filter cutoff.  You just don't want to attenuate your max desired frequency.  So now my sample rate needs to be at least twice the cutoff frequency to avoid aliasing.  So I would probably choose 5kHz for my sampling frequency.

 

Notice that there's no true rhyme or reason to my numbers.  Just the rules that your cutoff needs to be slightly higher than you max signal frequency and your sampling rate needs to be at lease 2x your cutoff frequency.

 

 

Actually, this is my first time to do vibration analysis, so it is fairly difficult to make a clear concept of sampling rate, bandwidth, and frequencies..

I am trying to pick up as many natural frequencies as I could with 4 accelerometers on the mini blade.

(it is difficult to answer the frequencies I wanna pick up.)

I guess the max frequency might be several hundreads.

So, If the max frequency is 500 Hz, I need to add low pass filter at 800 to 1000 Hz. If so, I need to choose at least 1k Hz multiplies at least 2??

like over 2k Hz??

 

Sorry for keeping questioning you.

 

 

 

 

 

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I guess the max frequency might be several hundreads.

So, If the max frequency is 500 Hz, I need to add low pass filter at 800 to 1000 Hz. If so, I need to choose at least 1k Hz multiplies at least 2??

like over 2k Hz??


Sounds like you're getting it.

If we say the max desired frequency is 500Hz, 800Hz cutoff sounds quite reasonable.  Yes, you need AT LEAST 2x that for your sampling rate.  2kHz should work, but I would bump it up just a little bit, to something more like 3 or 4kHz.


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Cheers~~~~!

You saved my weekend~! ^^

 

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