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Setting the Samples to Read and Rate (Hz) in Continuous Mode in DAQ Assistant, for a NI USB-6001 with a Maximum Sampling Rate of 20kS/s

I would really like some advice please in understanding the relationship between the NI USB-6001 and the LabVIEW DAQ Assistant, pertaining to the setting of the Samples to Read and Rate (Hz) in Continuous Mode in DAQ Assistant, for a NI USB-6001 with a Maximum Sampling Rate of 20kS/s.

 

Am I correct in my understanding that the NI USB-6001 ADC can only sample up to 20kS/s, and is this therefore the upper limit for the Samples to Read and Rate (Hz) settings in DAQ Assistant?

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Hi Ted,

 

here's the manual for your USB6001!

 

 

It clearly says: "20kS/s (aggregate)": You can read one channel at 20kS/s or two channels at 10kS/s or 4 channels at 5kS/s. Do you get the scheme?

 

The relation between "Samples to read" and "Rate" is quite simple: t = "samples to read" * "Rate"…

Best regards,
GerdW


using LV2016/2019/2021 on Win10/11+cRIO, TestStand2016/2019
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Hi GerdW,

 

Thanks for your quick response, however I already know the maximum sampling rate of the NI USB-6001 as prevously stated.

 

My question is to the relationship between the NI USB-6001 ADC threshold, and the DAQ Assistant settings for an input recieved from said device. (considering single channel only)

 

So by your explaination if I wanted to sample a signal at 200 Hz, I would be limited to 100 Samples to Read for this NI USB-6001 device?

 

The DAQ Assistant will let me enter much larger values than these, without any noticeable issues which is where my query on the relationship begins.  If the NI USB-6001's ADC sample-and-hold before quantisation is a limiting factor, i should see the effects of this, but don't? 

 

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Hi Ted,

 

if I wanted to sample a signal at 200 Hz, I would be limited to 100 Samples to Read for this NI USB-6001 device?

Please explain "signal at 200Hz"!

Do you want to measure a signal with a main frequency component at 200Hz - or do you want update rates of your FP (or data analysis) of 200Hz?

 

The DAQ Assistant will let me enter much larger values than these, without any noticeable issues

Really? No "noticable issues"?

Let's make a test: read 200 Samples at 20kS/s, then read 200kSamples at 20kS/s. It will make a difference!

Again the relationship between "Samples to read" and "sample rate" is "t" - the time it takes to read the samples: t := "samples to read" * "sample rate"…

Best regards,
GerdW


using LV2016/2019/2021 on Win10/11+cRIO, TestStand2016/2019
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Hi GerdW,

 

Now I understand the DAQ assistant settings, thanks.

 

So the Samples to Read is the buffer size, and the Rate (Hz) is actually the Samples/second (S/s).

 

So as my NI USB-6001 has a maximum sampling rate of 20,000 S/s, I can set the Rate (Hz) anywhere between limits of 0 and 20 kHz, in my case it is set to 200 Hz.  I had incorrectly assumed the Samples to Read to be directly related to the device sampling rate, where in reality I can set this freely, affecting only the front panel update time and resolution.

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Hey! 

I am kind of having the same issue here. I do not understand why you say t=samples to read*rate?

As you mentioned:

samples to read = how many samples we want to read 

rate=how fast we want to read the samples

then isn't t should be samples to read/rate instead of *?

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Hi karenzzuzzu,

 

yes, you're right. Probably a typo…

Best regards,
GerdW


using LV2016/2019/2021 on Win10/11+cRIO, TestStand2016/2019
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