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ETS mode and Auto Trigger After

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ETS mode and Auto Trigger After

Postby RFCiv » Thu Sep 28, 2006 9:53 pm

I have a PicoScope 3206 and was attempting to use ETS mode and wanted to use the the Auto Trigger After triggering capability. I have written my own software and setting the ETS mode to fast and setting the trigger with the Auto Trigger After to a given value appears to work fine(no errors are reported by the set_ets_mode or set_trigger functions), until you run the block and the device never triggers. Using the PicoScope software it is impossible to have both the ETS Mode and Auto Trigger After checkboxes checked at the same time. So I am assuming that these two features cannot be used together(there is no mention of this in the documentation, however).

I am trying to collect a sine wave that repeatedly sweeps in one direction only(like the 3206's function generator with a repeated sweep without dual slope). The frequencies are such that ETS mode is needed. I know the duration of the total sweep(the time it takes to go from the start frequency to the stop frequency) and wanted to set the trigger to trigger after that time such that a reliable ETS reading can be taken.

Question 1: Can ETS mode be used to capture a repeating sweeped signal?
Question 2: Can ETS mode and Auto Trigger After be used at the same time? The PicoScope software does not allow it; is it possible with my own?

Postby Michael » Fri Sep 29, 2006 9:59 am


Thank you for your post.

ETS is a way of increasing the effective sampling rate when working with repetitive signals. It is controlled by the ps3000_set_trigger() and ps3000_set_ets() functions.

ETS works by capturing many instances of a repetitive waveform, then combining them to produce a composite waveform that has a higher effective sampling rate than the individual instances. The scope uses special circuitry to add a tiny variable delay, a small fraction of a single sampling interval, to each trigger event. This shifts each capture
slightly in time so that the samples occur at slightly different times relative to those in the previous capture. The result is a much larger set of samples spaced by a small fraction of the original sampling interval. The maximum effective sampling rates that can be achieved with this method are listed in the Specifications table.

Because of the high sensitivity of ETS mode to small time differences, you must set up the trigger to provide a stable waveform that varies as little as possible from one capture to the next.

The ETS mode is dependant upon a stable trigger, you will not be able to use auto trigger after as this will upset the previous waveform data points.

Best regards,
Michael - Tech Support
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