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Two timescales

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Two timescales

Postby torbjorn » Fri Apr 26, 2013 8:09 am

Hello,
I have a need of recording single shot data with high resolution in time for the beginning, and later the time resolution could be lower.
Typically we have done with two channel recording on separate timebases.
Is there a possibility with an PicoScope 4227 to do something like that?
I don't see that the two channels can be on differnt timebases, so I am thinking about alternatives.
Nonlinear timebase and a single channel?
Switch timebase, say after 10-50 us, to a 0.1-100 second timebase, on the same channel?
Any other possibilities, or ideas.
Regards,
Torbjörn
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Re: Two timescales

Postby Martyn » Mon Apr 29, 2013 10:55 am

How many samples of data are you looking to capture in each part of the trace ?
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Re: Two timescales

Postby torbjorn » Mon Apr 29, 2013 4:16 pm

Thanks for responding,
The transient signal can in many cases be described by a sum of 2 exponentials, so recording say 1000 points at high speed for the first interval, and then say 10K - 100K points for the slow part, and baseline, would probably represent the data just fine.

Y = A* exp-(t/T1)+B*exp-(t/T2)

If the difference between T1, and T2 is large, recording one vector to cover both decaytimes would require a very (too) large vector.
Am I correct that the 4227 can do 128 ms at 4 ns sampling interval in single shot mode? (A total of 32 MS for one chanel) ?
Maybe two 4227 in parallel would make the task easier?

Regards,
Torbjörn
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Re: Two timescales

Postby Martyn » Tue May 07, 2013 10:46 am

Changing timebase would require a reconfiguration and rearm of the scope and potential data loss.

Looking at the detailed part of your signal, 1000 samples for 50us would then enable you to continue and capture a further 12 seconds of data without data loss, 1000 samples for 10us only just over 2 seconds.

Two scopes or a scope with deeper memory may be the only option.
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