Rigol DHO1000 Series Cursor Control in a Zoomed Window Issues

[scopeman]

I have discovered a fairly serious bug with recently released firmware version 2.13.00.07 when used with my DHO1204. This issue probably applies to all in the series and in addition to the DHO4000 series as well. It is possible that this error existed with earlier firmware but the latest firmware is the only version I have.

Maybe someone can confirm this. It would be interesting to see if the DHO800/900 series have this problem as well,

To repeat the bug:

1. Connect and trigger on a 10MHz signal to Channel 1 or probably any channel.
2. Set the acquisition depth to 10Mpts.
3. Set the main timebase to 50uS/division.Note that the sample rate is 500MHz 2ns per sample point.
4. Activate Zoom.
5. Set the Zoom timebase to 100nS/division. 
6. Note that the cursor knobs can move AX and BX anywhere within the window.
The bug:
7. Now set the Zoom timebase to 50nS/division or faster.
8. Note that it is difficult, if not impossible, to place the cursors within the zoomed area and if you are able to do so the cursors will not stay in the zoomed area.
Note that the cursors should be able to be positioned anywhere within the zoomed area and be able to be positioned at any one of the sample points in the window. 
9. If the Zoom timbase is reduced to 100nS or below the cursors work normally.

Sam
W3OHM

[TurboTom]

I can reproduce this observation, also F/W 2.13.00.07. But this is only valid for cursor mode "manual" which appears to be somewhat broken anyway. If you select cursor mode "track", you can adjust the cursors as expected. I guess Rigol should have a look at the "manual" cursor mode...

[scopeman]

Thank you TurboTom for your assistance.

I confirmed that changing the cursors to "track" does fix the problem. I sent Rigol a note and outlined the procedure to confirm the bug.

This is what I sent them:

"This morning I changed the setting on the cursors from manual to track and I can position the cursors anywhere in the zoom window no matter what the zoom timebase setting. If I switch back to manual I can not do so. So this confirms that the error is the same on my scope as another user with the identical scope. I would not be surprised if you see this on the DHO4000 series as well as my HDO1000 series (HDO1204) scopes as well. I am convinced now that this is a firmware issue not a hardware one.

I have devised a simple way to illustrate this using only a single shot capture using only a scope probe and the scope's own calibrator output. This should take only a few minutes to set up and illustrate the problem when the cursors are in manual mode.

Setup example:

1.Connect a scope probe to CH1 and to the calibrator output. Set the scope to trigger on CH1.
2. Set the Main Horizontal time base to 1mS/div. Press Run/Stop to stop the sweep
3. Set the Acquisition to Normal and the  Mem Depth to 10M Roll mode to OFF
4. Press Single and trigger the sweep
5. Activate the Zoom mode
6. Press Cursor and select setting in the result pane and set the mode to manual (this is usually the default setting).Close the setting window.
7. Move the cursors inside the Zoom window with AX/BX centered on an edge.
8. Advance the Zoom timebase in steps stopping the timebase setting at 2.00uS/div while keeping the cursors centered on an edge.
Note that you can freely move cursor AX or BX anywhere within the zoomed area.
9. Re-center the cursors on an edge.
10. Advance the Zoom timebase to 1uS/div. Now move the BX cursor. Note that the cursor jumps out of the window and you can not easily position it in the Zoomed window. Returning the Zoom timebase one step back to 2uS/div and note that normal cursor operation is possible.
11. In the results pane touch the cursor readout and again select setting and change the cursor mode to Track. Close the setting window.
12. Note that you can now adjust the Zoom timebase all the way to 2.00nS/div and you are able to set the AX/BX cursors anywhere in the zoom window.

Observation:

The point at which in manual cursor mode the cursors fail to work properly seems to depend upon the setting of the main timebase, the acquisition depth and the Zoom timebase setting."

Sam
W3OHM
"scopeman"