Issue with maths functions

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CDBS
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Issue with maths functions

Post by CDBS » Thu Apr 26, 2018 6:35 am

Hi

I am having an issue with the continuity of the maths functions. On each recorded screen every new screen the math line resets at the start so I loose continuity between screen boundaries when looking at changes.

I there anything that can be done to stop the reset.

Gerry
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Re: Issue with maths functions

Post by Gerry » Thu Apr 26, 2018 3:33 pm

Hi CDBS,

The short answer to your question is No, but you may be able to change where this happens in your data, so that the discontinuity doesn't affect what you want to see.

One reason for the discontinuity is that Math Channels, in PicoScope 6, are display functions (which can be saved to a file) so, at any one time, they only apply to the information currently in the display. In PicoScope 6, each 'recorded screen' is stored in the Waveform buffer as one waveform of data, and once the capture of a waveform is complete and all of the sample data is there, only then can the Math function can be applied to the data. This is because, for instance, some Math functions work on groups of data and need the data to be accessible before the processing can be started, and some Math functions are relative to Time T=0, where zero is the instant that the trigger occurred, and as you can only have one waveform per trigger those functions only can be applied to one waveform.

The other reason is that the Trigger is a hardware function that requires setting up in between captures (known as re-arming) in preparation for starting the next capture, and this takes a finite amount of time (anything from less than a microsecond to many microseconds, depending upon the sample rate being used). So, even if you could apply the maths to straddle between waveforms, you would have gaps in your data because of the time required to re-arm the Trigger.

If want to apply Math channels to more of your waveforms without any discontinuity (i.e. to data acquired over a longer duration of time) then you would need to increase the capture period by increasing the Time per division in the Timebase. If this reduces your sample rate too much then you may be able to use more samples per buffer (speeding up the sample rate) by increasing the 'Number of Samples' requested (in the text window to the right of the Timebase). Note that you can see your 'Sample Rate', 'Number of Samples' you actually get per waveform, and other useful data at a glance by opening a Properties Pane in your display (under the Menu option 'Views->View Properties').

Regards,

Gerry
Gerry
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CDBS
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Re: Issue with maths functions

Post by CDBS » Tue May 01, 2018 8:19 am

Thanks Gerry
Your reply was extremely comprehesive and very useful.

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