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Dual timebase

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Dual timebase

Postby guest » Wed Jan 24, 2007 12:15 am

Do the Picoscopes have a dual timebase facility such as that found on the ancient Tektronix 'scopes I used to use years ago... ie. the horizontal trace is in two parts, the first at, say, 10ms/div, the second at, again say, 100us/div, the crossover point determined by a delay time or a trigger event?

Thanks.
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dual time bases

Postby Autonerdz » Wed Jan 24, 2007 1:00 am

I am not familiar with that Tektronix model but you can have two scope windows within PicoScope open at the same time. Each window can have completely different settings. Different triggers, timebase, voltage, filters, etc. The windows take turns sampling.
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Postby Guest » Wed Jan 24, 2007 5:41 pm

Thanks for the response, it seems that the scope doesn't have the feature I'm looking for. Just to be certain, maybe I can clarify what I'm asking.

A dual timebase facility is needed when the event you want to capture is relatively high-speed, but occurs a (relatively) long time after another event. For example, let's say that a switch closure triggers the transmission of 10 bits of data at 10us/bit. The switch has to be debounced for 50ms, say, before the data is sent. To examine the transmitted data, the first timebase could be triggered at 10ms/div, with the second timebase triggered after a delay just less than 50ms, or (better in this case) triggered by the start of the data transmission, and running at 20us/div (this assumes that there are 10 divisions horizontally).

Without a dual timebase facility, it is difficult to capture the data.

So - following on from your reply - if this cannot be done in the traditional way, can the second window be triggered following events in the first window?
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dual time bases

Postby Autonerdz » Wed Jan 24, 2007 7:23 pm

I work with the automotive scopes and software. There may be a way to do what you want that I am unaware of. The automotive software is somewhat different. I mistakenly listed trigger as able to be different in the windows. I'll go to my corner now. :? This is only true for PicoScope 6 auto (beta). 5.15.4 auto doesn't allow separate triggers. The standard scope software may be different.

Trigger is common to the windows and the scope will wait for trigger for window 1, then for window two....The trigger in window one will not trigger window two. (with PicoScope 5.15.4 auto) You can, of course, time delay the trigger.

This may be a non issue because the deep memory models can acquire very long times with high sample rates so it may be as simple as putting more time on the screen to catch your second event. For example, using my 3423 scope, I could easily trigger on a switch and have an event on a second channel 50ms later (using 10ms/div), maintaining a sample interval of 400 nanoseconds (plenty for your 10us bits). You could then zoom in to examine the data bits. Other PicoScope models are much more powerful than this one.

I'll get out of the way and let the Pico staff to give you a more definitive answer that applies to the non automotive software.
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Postby Guest » Sat Jan 27, 2007 3:21 pm

Good point about the deep buffer - as you say, in some cases, that would be sufficient.

Thanks again for taking the time to reply.
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