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Sampling rate

I have a amplifier which gives me a gain of 1000 and a low pass filter value of 53Hz. I am inputting this signal to NI-USB but the minimum sampling rate of it is 1000 Hertz. How can i decrease the sampling rate of NI Usb ?

Help guys I am very confused in sampling rate and how it works

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Hi yum,

 

which hardware do you really use? NI-USB is certainly not the correct label...

Best regards,
GerdW


using LV2016/2019/2021 on Win10/11+cRIO, TestStand2016/2019
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Sorry i forgot to mention its NI USB 4431

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You can sample at whatever rate you want. Generally you want to be sampling faster than your source, so just keep it at 1 kHz.

 

The sample rate is how fast the DAQ device records the input voltage. The low-pass rate is the fastest sine wave that will be transmitted through the amplifier. Though both are in Hz you can't directly compare the two.

 

If you sample a 53 Hz sine wave at 53 Hz you'll just see a row of constant points! If you want to see a nice smooth sine wave, sample at 10x or 100x the wave frequency. At 1000 Hz sample rate, you'll get 18 points per wave, which should be plenty.

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And what about the number of samples ? If input analogue signal peaks at 53 Hz and the sampling rate of DAQ is 1k Hz then how much should be the number of samples ?

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Hi Yum,

 


@Pukhtun_Yum wrote:

And what about the number of samples ? If input analogue signal peaks at 53 Hz and the sampling rate of DAQ is 1k Hz then how much should be the number of samples ?


You define number of samples according to your requirements!

There is a simple formula describing the relationship: time * samplerate = NumOfSamples

 

(For continuous reading I advise to read 1/10 the samplerate, so at 1kS/s I would read 100 samples per iteration...)

Best regards,
GerdW


using LV2016/2019/2021 on Win10/11+cRIO, TestStand2016/2019
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What if the number of samples are greater than sampling rate ? How would it effect the measurement ?

Like for example if sampling rate is 1000 and number of samples are 2500

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@Pukhtun_Yum wrote:

What if the number of samples are greater than sampling rate ? How would it effect the measurement ?

Like for example if sampling rate is 1000 and number of samples are 2500


2500 Samples) / (1000 Samples/second) = 2.5 seconds

 

So it will take 2.5 seconds to take that data.


GCentral
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