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Increasing Recording Sampling Rate (Pico2205)

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Increasing Recording Sampling Rate (Pico2205)

Postby Steven » Tue Dec 29, 2009 3:02 pm

I am using the latest PicoLog software with the aim of recording signals at around 78KHz. The Problem is that when trying to set the sampling frequency in the PicoLog Software (Settings/Sampling) i.e through the Samping Interval - the minimum sampling interval you are able to set is that of 1 ms. (It is indicated in the help that you can only enter whole numbers i.e 0.05 ms would be invalid).

Given that the Pico2205 is listed with a sampling frequency of 200MS/s how can I achieve a sampling frequency adequate for my application.

Thanks in advance for your time.

Steven
Steven
 

Re: Increasing Recording Sampling Rate (Pico2205)

Postby PeterF » Tue Dec 29, 2009 4:39 pm

Hi,
PicoLog software is intended for use when logging slower waveforms for long periods of time. The fastest sample rate that can be set is 1mS in "Continuous sampling" mode and in practice you will not achieve this. You can set Picolog into "Fast sampling mode" but then you might as well use our PicoScope6 software which is far superior at high speed. In PicoScope6 adjust the sample rate by selecting the number of samples per screen capture. The time period of each screen capture is set by adjusting the time per division (10 divisions).
The 2205 is in "Block" mode for screen times of 1 sec or faster. It is in "Streamimg" mode at 2 secs and longer. (Screen time is the time/division x10).
Here are some example results:-
Block Mode:-
Speed Screen time Samples per screen
40MS/s 10uS 406
40MS/s 100uS 4006
5MS/s 1mS 5006
625KS/s 10mS 6256
78KS/s 100mS 7818
4.8KS/s 1 sec 4888

Streaming Mode:-
Speed Screen time Samples per screen
1MS/s 2 secs 2MS
333KS/s 5 secs 2MS
200KS.s 10 secs 2MS
100KS/s 20 secs 2MS
10KS/s 200 secs 2MS

In Block mode, the input signal is fed into the SCOPE buffer memory, (max of 16KS on the 2205, shared between the number of active channels) and then sent to the PC over the USB connection. Up to 1,000 consecutive but separate screens of data can be held in PC memory for later saving to disk.
In Streaming mode the limitation is in Picoscope6 which limits the maximum number of samples per screen to 2MS. The input signal does not use the Scope buffer memory at all, the data is sent directly over the USB connection into the PC buffer memory (RAM). The downside of using a large (2MS) screen size is that it takes just over 1 second to transfer to PC RAM, thus there is that gap in the recorded data.
All data, in both block mode & streaming mode is saved to PC RAM only during recording and can only be saved to Hard Drive after recording has stopped.
These screens can easily be saved all at once to hard drive in psdata format for later reloading into PicoScope6 and review.
I hope that helps,
PeterF.
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Re: Increasing Recording Sampling Rate (Pico2205)

Postby Steven » Wed Dec 30, 2009 11:34 am

Thanks Peter Your information was helpful.
Just to clarify, from what you said it would seem that the Pico2205 cannot record an indefinte amount of data onto the PC because data has to be transfered from memory to the Harddisk after recording. So effectively there is a limit to how much data I may record.Is this limit determined by the size of RAM I have?
Steven
 

Re: Increasing Recording Sampling Rate (Pico2205)

Postby PeterF » Sat Jan 02, 2010 4:49 pm

Hi Steven,
Here is an article on Streaming mode:-
kb/kbfiles/PicoScopeUSBStreaming.pdf
Maximum record length with the 2000 series scopes is 2MS. The maximum number of 2MS screens of data that can be held in PC memory is affected by the amount of PC memory. If you write your own routine for data capture and continuous, direct saving to hard drive then the only limit is the hard drive size.
PeterF.
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