Strange AD2 'scope behavior

[Sid Price]

I have an issue with the scope of my AD2. I spent a long time trying to figure out why I was not seeing a 400KHz square wave on the output of my MCU. However, when I used the logic  instrument it showed the signal. Eventually I switched to a different scope and the signal was indeed present and looking good.

What I have found is that if the mode is set to "screen" I see a DC voltage of about half the supply rail, however, when I change to "Repeated" the signal appears once again. I also see some very strange captures when I record the signal, it should be continuous, the recording shows it as not so and the trace displayed covers only half of the screen.

Is my AD2 broken or is there some setting I may have messed up.

 

[attila]

Hi @Sid Price

Please attach some screenshots or photos.

[Sid Price]

OK, will do. Sorry I missed tour reply, I didn't get a notification from the forum. :(

 

Hopefully I can post the screen shots later today.

Thank you again.

[Sid Price]

Hi @attila, I made a screen capture video of the issue.

 

https://sidprice-my.sharepoint.com/:v:/p/sid/EdFLPpuBkqROt0LyqCW3DjkBVNhaWcUudqz4TT29nYvfQw?e=rhg13f

Thanks.

[attila]

Hi @Sid Price

Notice when you change to scan Screen/Shift the Time base changes to 100ms/div, so you get a zoom-out view.

[Sid Price]

@attilaThanks for pointing that out ... why does the instrument do that? Seems a little user hostile to me.

I have neve seen a 'scope to that and I have worked with them for many, many years.

[attila]

Hi @Sid Price

Thank you for the observation.

The scan modes make sense only with second or higher spans, in order the signal evolution to be visible.
The time base change can be seen in the control field, in the bottom ruler, in the top status sample rate. 
The slow movement of the capture and/or vertical line indicating the scan progress should also give a hint for slow acquisition.

At the moment I have no idea how to make this better or what to add to be more evident.

[Sid Price]

@attilaWhat would be an improvement is that when using "Screen" if one adjusted the time-base so the signal is displayed the instrument would stay on that time-base when the Screen display was next selected. This would at least make the instrument more reliable. It would be especially helpful if it did not adjust the time-base automatically at all, just stay on whatever the other modes are using. Chances are for a particular workspace all the modes are going to require being at similar time-bases.