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Block mode, how to chose number of segments?

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Block mode, how to chose number of segments?

Postby sqi » Wed Jul 28, 2010 12:28 pm

Hi Support,

I want to perform fast sampling on a Pico4424 to monitor a signal during an undefined period of time. So I am considering using Block mode:

Code: Select all
1. Setup device
While monitoring is on
{
  2. ps4000RunBlock()
  3. ps4000GetValues()
  4. Do someting with data and then discard it
}


In that case, is there any reason to segment my buffer? Or is Streaming mode more appropriate?

Thanks in advance
Julien
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Re: Block mode, how to chose number of segments?

Postby Robin » Wed Jul 28, 2010 1:37 pm

Hi Julien

In streaming mode, you get a continuous stream of data. However, the sampling rate is limited by the USB trasfer rate.

Block mode allows much higher sampling rates, but there will be gaps in the data. If you are waiting for a particular event to occur, then you can set the oscilloscope to trigger on that event, ensuring that it is not missed.

Unless you want to keep multiple blocks of data on the device at once, you don't need to use segmentation.

The choice of sampling mode depends on your requirements in terms of sampling rate and whether you need to capture more samples continuously than can be stored in the device's memory.

Robin
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Re: Block mode, how to chose number of segments?

Postby sqi » Thu Jul 29, 2010 7:33 am

Hi Robin, thanks for the insights.

Then, concerning rapid block mode, documentation says: "rapid block mode allows you to sample several waveforms at a time with the minimum time between waveforms."

As far as I understand, the rapid block mode is relevant only when buffer needs to be segmented: I can sample as many data with no gap in normal block mode if I setup a large buffer with less (or no) segment. Am I correct?

Julien
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Re: Block mode, how to chose number of segments?

Postby ziko » Mon Aug 02, 2010 10:28 am

Hi,

In block mode, the scope stores data in the RAM and then transfers it to the PC. Between each block of data there is an associated trigger re-arm delay (which can be in 10s of milliseconds). Uses same segment. For more information please refer to the programmers manual under section 4.6.1.1

Whilst in Rapid block mode the scope captures all the waveforms until the buffer is full and then transfers the data across. This reduces the gap between waveform buffers to about 2.5 microseconds. The memory would be segmented, for more information please refer to the programmers manual under section 4.6.2.1

http://www.picotech.com/document/pdf/ps4000pg.en-4.pdf

Kind regards
Ziko

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Re: Block mode, how to chose number of segments?

Postby sqi » Wed Aug 04, 2010 7:34 am

Thank you for support
Julien
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