Time difference between analogue and digital signal

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PhilB
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Time difference between analogue and digital signal

Post by PhilB » Thu Oct 10, 2019 12:41 pm

Hello
As the title says, for the same signal connected to an analog channel and to a digital channel, there is a shift between the two signals of 70 μs.
The hardware is a Pico 3403D MSO-Version 1.7.5.0 / 1.0.66.0
Thanks for your help
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bennog
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Re: Time difference between analogue and digital signal

Post by bennog » Thu Oct 10, 2019 3:09 pm

Are you sure both inputs are connected to the same data line.

A simple test over here with bult in signal generator shows no time difference at all.
2019-10-10_16-56-51.png
See above screen shot. Same scope as you have and time-base set at 200 ns /div

Benno

PhilB
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Re: Time difference between analogue and digital signal

Post by PhilB » Mon Oct 14, 2019 7:57 am

Yes, it's the same signal connected to analog and digital signal
Look the pulse on P31 (digital channel (green)) and on channel B (red) is the same pulse : time shift =70µs
Phil

bennog
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Re: Time difference between analogue and digital signal

Post by bennog » Mon Oct 14, 2019 2:51 pm

can you post a psdata file (possible with muliiple traces)

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PhilB
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Re: Time difference between analogue and digital signal

Post by PhilB » Tue Oct 15, 2019 12:56 pm

Hello

I saved only this psdata file, but it shows the problem, I could redo the manipulation if necessary
Thanks
PhilB
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bennog
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Re: Time difference between analogue and digital signal

Post by bennog » Wed Oct 16, 2019 6:50 am

ok that is not 70 but 64 us (or 63.8 us) depending on where you measure.
At 8 ns sample interval this is 8000 samples.

Looking at the interference from the SCK signal on the analoge measurement I see exactly 64 us.

This is in all the 32 samples you posted exactly the same.
I guess something went off from some sort of hick up in the software.

Have you tried powering the PC and the SCOPE down and up again after 30 seconds.
Be sure to power the scope completely off (so no external power and no USB)

And then redo the same measurement and test ?

Benno

Martyn
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Re: Time difference between analogue and digital signal

Post by Martyn » Wed Oct 16, 2019 8:26 am

We are aware of an issue where the digital channels are out of sync when you enable filtering on any of the analog channels, and are looking at a resolution for this.

Can you repeat your test turning off the filtering on Channel D and see if this fixes the problem for you.
Martyn
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PhilB
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Re: Time difference between analogue and digital signal

Post by PhilB » Wed Oct 16, 2019 9:42 am

Hello
I unplugged the picoscope from its power supply and USB port for 30s
I redid a measurement under other conditions:
The analog channel A on a radio signal (data RF) AND the analog channel D12 on the same signal Data RF
This time, we see the shift (63us) on the entire signal
Look at the attached file : psdata
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PhilB
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Re: Time difference between analogue and digital signal

Post by PhilB » Wed Oct 16, 2019 9:55 am

Sorry martyn,
I had not yet seen your message, removing the low-pass filtering on the analog channel D, the signal is no longer shifted and is well synchronous between analog and digital channel
Thank you ! I let you do
Phil

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