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3204A limited to 1.25M samples?

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3204A limited to 1.25M samples?

Postby va3ttn » Tue Nov 20, 2012 4:52 pm

I'm unable to get more than 1M or 1.25M samples with a single channel active on 3204A.
With two channels active I can't get more than 625k samples per channel.
The signal generator is turned off.

So, how do I approach the advertised 4M samples?

Help, About dump follows:

PicoScope® 6 - PC Oscilloscope software version: 6.6.46.1
Copyright © 1995-2012, Pico Technology Ltd

Model: PicoScope 3204A
Serial Number: AV700/222
USB Version: 2.0
Calibration Date: 08 June 2012
Hardware Version: 1
Driver Version: 1.0.0.263
Firmware Version: 1.1.0.0 / 0.5.8.0

The computer is HP Probook 6560b with 8 GB RAM.

Sinisa
va3ttn
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Re: 3204A limited to 1.25M samples?

Postby va3ttn » Tue Nov 20, 2012 7:02 pm

The above results were obtained with total collection time of 20 ms,
because I bought this unit specifically to sample a single channel
for 20 ms using the sampling rate of at least 100 Ms/s,
which amount to 2M samples.

But now it seems that my prospects of achieving the goal are very low.

Here are the sampling rates and record lengths for all the available collection times.

Code: Select all
Conditions:
  A channel on, +/-50 mV, DC
  B channel off
  signal generator off
  maximum waveforms = 1
  horizontal zoom = 1
  requested record size = 4 M samples


total
collection   sample        sample       no.
time         interval      rate         samples
--------------------------------------------------
   20 ns       2 ns        500 Ms/s     15 (120)
   50 ns       2 ns        500 Ms/s     30 (120)
  100 ns       2 ns        500 Ms/s     55 (110)
  200 ns       2 ns        500 Ms/s     105
  500 ns       2 ns        500 Ms/s     255
    1 us       2 ns        500 Ms/s     505
    2 us       2 ns        500 Ms/s     1,005
    5 us       2 ns        500 Ms/s     2,505
   10 us       2 ns        500 Ms/s     5,005
   20 us       2 ns        500 Ms/s     10,005
   50 us       2 ns        500 Ms/s     25,005
  100 us       2 ns        500 Ms/s     50,005
  200 us       2 ns        500 Ms/s     100,005
  500 us       2 ns        500 Ms/s     250,005
    1 ms       2 ns        500 Ms/s     500,005
    2 ms       2 ns        500 Ms/s     1,000,005
--------------------------------------------------
    5 ms       4 ns        250 Ms/s     1,250,005
   10 ms       8 ns        125 Ms/s     1,250,005
   20 ms      16 ns        62.5 Ms/s    1,250,005
   50 ms      32 ns        31.25 Ms/s   1,562,505
  100 ms      48 ns        20.83 Ms/s   2,083,339
  200 ms     112 ns        8.929 Ms/s   1,785,720
  500 ms     256 ns        3.906 Ms.s   1,953,130
    1 s        1 us        1 Ms/s       1,000,005
    2 s        1 us        1 Ms/s       2,000,005
    5 s        2 us        500 ks/s     2,500,005
   10 s        3 us        333.3 ks/s   3,333,339
   20 s        5 us        200 ks/s     4,000,005
   50 s       13 us        76.92 ks/s   3,846,159
  100 s       26 us        38.46 ks/s   3,846,159
  200 s       51 us        19.61 ks/s   3,921,574
  500 s      126 us        7.937 ks/s   3,968,259
1000 s      251 us        3.984 ks/s   3,984,069
2000 s      501 us        1.996 ks/s   3,992,021
5000 s    1.251 ms        799.4 s/s    3,996,808
10000 s    2.501 ms        399.8 s/s    3,998,406
--------------------------------------------------


Up to 2 ms total collection time everything is as expected.
At 5 ms one should have expected 500 Ms/s and 2.5 M samples,
well within the advertised 4 M samples, but only 1.25 M samples are possible.

Apparently, 3204A won't go above 2 M samples until the sampling rate
is low enough (500 ks/s) that it can start using PC memory instead
of its own fast and very expensive memory.

I still hope that there is a gross mistake in my tests, as I only have the unit for 2 hours.
Can somebody enlighten me?
va3ttn
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Re: 3204A limited to 1.25M samples?

Postby Martyn » Wed Nov 21, 2012 8:31 am

If you are free running, or using repeat/auto triggers, and 1 channel enabled you will only have half of the memory available to fit a waveform in. If you enable single trigger then the full memory will be used.
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Re: 3204A limited to 1.25M samples?

Postby va3ttn » Wed Nov 21, 2012 11:23 am

That worked, thank you!

May I suggest that such an information deserves a prominent place
in the documentation, perhaps even somewhere in the user interface.
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Re: 3204A limited to 1.25M samples?

Postby Martyn » Thu Nov 22, 2012 10:46 am

Thanks for the suggestion I will pass the information on
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