Capture stops, shimmies back, then continues. Weird

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AlexMpico
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Joined: Sun Jul 01, 2018 7:20 am

Capture stops, shimmies back, then continues. Weird

Post by AlexMpico »

Hi, I have a strangely behaving waveform on an Ignition firing event and Cam signal capture (automotive).

On Auto or Repeat, waveform for 2 traces reaches the trigger point (triggering on ignition capture) halts, shimmies back perhap 1/c of a time Div maybe 2-3 times, then continues on its merry way.
Happens about 3 our of 4 screen traces.
I using a x1 on Cam sensor and an Ignition inductive pick up on ignition or a coil-near-plug wasted spark Hyundai system.
No change if I disconnect Cam signal, but seems to behave if I drop the time base from 500ms/Div to 200ms/Div.
Only happened on last usage. Not noticed before.
Recently added a Picoscope to my collection (2205). Otherwise works wonderfully and lives up to Pico reputation.
The .psdata buffer capture doesn't really show it because it it a series of stills rather than a moving image.
However, I have attached anyway.
Any thoughts. Very puzzling Dance of the Waveform here!
Attachments
180701 Cyl 1 Idle Hyundai Getz -0001.psdata
(430.32 KiB) Downloaded 365 times

Martyn
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Re: Capture stops, shimmies back, then continues. Weird

Post by Martyn »

You are performing a streaming capture with a trigger, so I believe what you are seeing is correct behaviour.

Data will appear from the left of the screen and continue until the trace reaches the trigger diamond, 0 seconds on the x axis. It will then continue to draw data at this point, forcing the previously drawn trace to scroll off the left of the screen, until the trigger condition is met. Once the trigger condition is met it will then continue to draw the trace to the end of the screen.

If you set trigger to "None" you would not see this.
Martyn
Technical Support Manager

AlexMpico
Newbie
Posts: 0
Joined: Sun Jul 01, 2018 7:20 am

Re: Capture stops, shimmies back, then continues. Weird

Post by AlexMpico »

Thank you Martyn, I believe you are correct. I will pay attention to this behaviour and try to reconcile with your comments.
I have another pico teething issue to do with the Reference Waveform Delay, which I'll post on this forum section. Not doubt you will see it
cheers
Alex

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