Author Topic: Rigol DS1000Z trigger edge type, alternate. Is this a bug?  (Read 2658 times)

0 Members and 1 Guest are viewing this topic.

Offline oliver602

  • Regular Contributor
  • *
  • Posts: 90
  • Country: gb
Recently got a Rigol DS1054Z. While playing around with it as a newbie I discovered behaviour which I thought was odd. Perhaps someone could help me understand what is going on here. Or maybe it is a bug.

I connect channel 1 to the test signal and select Trigger type as Edge and select Slope as alternate. See attached image. I expected to see both rising and falling edge displayed. But instead it only displays one edge, sometimes randomly switching between rising and falling. It seams to behave as expected when scale is at 1us or less per division. My previous scope (a DS1052E) displays both edges regardless of scale.
« Last Edit: May 12, 2015, 12:13:33 am by oliver602 »
 

Offline alsetalokin4017

  • Super Contributor
  • ***
  • Posts: 1959
  • Country: us
Re: Rigol DS1000Z trigger edge type, alternate. Is this a bug?
« Reply #1 on: May 12, 2015, 09:19:58 am »
What's the frequency of your test signal?  I can get similar behaviour but only for a very narrow range of frequency settings.
The easiest person to fool is yourself. -- Richard Feynman
 

Online ebastler

  • Super Contributor
  • ***
  • Posts: 3511
  • Country: de
Re: Rigol DS1000Z trigger edge type, alternate. Is this a bug?
« Reply #2 on: May 12, 2015, 09:39:47 am »
I connect channel 1 to the test signal and select Trigger type as Edge and select Slope as alternate. See attached image. I expected to see both rising and falling edge displayed. But instead it only displays one edge, sometimes randomly switching between rising and falling. It seams to behave as expected when scale is at 1us or less per division. My previous scope (a DS1052E) displays both edges regardless of scale.

The scope's waveform update rate may happen to be in sync with the test signal you are looking at. Hence, whenever the scope is ready to look for another trigger, the test signal is approaching another low > high transition. I understand that you are measuring the built-in 1 kHz square wave, which is most likely controlled by the same master clock as the scope's data acquisition system; so the signal may actually be phase-locked to the waveform update rate.

As mentioned by alsetalokin4017, I would expect this behavior to occur only for specific settings of the signal frequency and/or sampling rate and timebase. What happens if you change the timebase, number of samples, trigger hold-off time etc.?
 

Offline alsetalokin4017

  • Super Contributor
  • ***
  • Posts: 1959
  • Country: us
Re: Rigol DS1000Z trigger edge type, alternate. Is this a bug?
« Reply #3 on: May 13, 2015, 05:16:53 pm »
Ah... so by "test signal" what is meant is the scope's Probe Calibrator output. I see now.

Yes, when using the Probe Calibrator output I get exactly the same behaviour as described. And I believe that ebastler has given the correct explanation. It's not exactly a "bug" unless you want to include all the quirks of DSOs vs Analog scopes as bugs. It's a sampling error, that can be avoided by using different settings on the scope.
The easiest person to fool is yourself. -- Richard Feynman
 

Offline electr_peter

  • Supporter
  • ****
  • Posts: 937
  • Country: lt
Re: Rigol DS1000Z trigger edge type, alternate. Is this a bug?
« Reply #4 on: May 13, 2015, 05:56:02 pm »
Positive (or negative) signal slope is in sync with osciloscope's waveform update time and retrigger time. This behaviour is normal and expected under some circumstances.
"Alternate trigger" means that scope will trigger on both rising and falling edges. However, it does not mean that it will trigger on rising, then falling, then rising edge. Word "alternate" is used in a sense "use either falling or rising edge, whichever happens first".
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf