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Below shown is the screenshot of the GUI for Saleae logic analyser http://www.saleae.com/logic

I would like to know what is the meaning of "number of samples to collect" and "sample rate" ?

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As per my understanding, sample rate is how often samples are collected. Here it is shown 16MHz. so that means in one second, there are 16 mega samples collected.

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But then what is this "1 M samples" ? Is it 1 million samples per second (but then what is 16MHz) ?

Or is it like this

  1. in one second, we sample 16 Mega times
  2. and in each of this 16 Mega sample, we will take 1 Million samples ?

Please correct me. I am so much confused.

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The leftmost setting it the total number of samples per capture while the rightmost option selects the sampling rate.

1M samples, @16MHz : will gather 1M samples total with a rate of 16M samples per second. That means that the capture duration will be (1/16)=0.0625 second (1M/16M)

16M samples, @16MHz : will gather 16M samples total with a rate of 16M samples per second. That means that the capture duration will be (16/16)=1 seconds (16M/16M)

32M samples, @16MHz : will gather 32M samples total with a rate of 16M samples per second. That means that the capture duration will be (32/16)=2 seconds (32M/16M)

Choosing a different sampling rate

5M samples, @1MHz : will gather 5M samples total with a rate of 1M sample per second. That means that the capture duration will be (5/1)=5 seconds (5M/1M)

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  • \$\begingroup\$ Does this mean that 16M samples, @16MHz has a capture duration of 1 second and after 1 second, the measurement will stop ? \$\endgroup\$ – robomon Mar 22 '14 at 22:32
  • \$\begingroup\$ @robomon Yes, that is why I wrote in the reply for 16M/16M that the duration will be 1sec \$\endgroup\$ – alexan_e Mar 22 '14 at 22:33
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The 16 MHz refers to the sample rate while the 1 MHz is the actual number of samples taken. At a rate of 16 million samples per second, it takes 1/16 of a second to accumulate 1 million samples. Thus there is a tradeoff between sample rate and the number of samples. For a fixed sample rate, the sampling time is proportional to the number of samples.

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