Rigol DS2072A Statistics for simple pulse train incorrect. - Page 1
Forum section: electronics / testgear

author: iBeta
author_rank: Newbie
timestamp: March 23, 2017, 12:33:43 pm
content: The statistics shown in the scope are obviously not correct. I am beginning to regret buying this.

author: alsetalokin4017
author_rank: Super Contributor
timestamp: March 23, 2017, 12:41:40 pm
content: I'd hardly call that a "simple" pulse train, since you have two different periods happening.With that kind of pulse train, what numbers would you expect to see for the statistics?I agree that there is something wrong, but could it be because of the signal itself rather than the scope? That is, perhaps your signal is confusing the scope's measurement algorithms.

author: 2N3055
author_rank: Super Contributor
timestamp: March 23, 2017, 12:59:17 pm
content: There is no scope in the world that read minds .. no artificial intelligence either...So it can't know what do you think it should measure here.You have two shorter and one wider pulse. Which one do you want to measure? Or is that whole pulse train is one repetitive waveform?What is the start ? First short one, second short one, the wider one... Which ?Use cursors, that is the reason they exist. Try enabling auto cursors. They show you what is scope using for the particular measurement.It will probably make more sense then..

author: iBeta
author_rank: Newbie
timestamp: March 23, 2017, 01:23:30 pm
content: QuoteIf not I would of written 'simple square wave'.QuoteI am not asking it to read minds, just the oscilloscope data.Let's take the statistics for the +Width; it has an average, minimum and maximum values. I would expect that the minimum width figures out the shortest time that the signal is at +V.Looking at the image, that appears to be around 400us on the visible data.Not rocket science people.

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: March 23, 2017, 01:32:23 pm
content: +Width and -Width are both wrong

author: alsetalokin4017
author_rank: Super Contributor
timestamp: March 23, 2017, 02:00:58 pm
content: If it's any consolation for you, I can also confuse my DS1054z with a similar pulse train. The stats are totally wrong and don't even update after a while, just as in your scopeshot.I wonder what a high-end scope from, say, Tek or R&S would do when asked for stats on that kind of pulse train.I don't know any rocket scientists that use Rigol scopes.

author: PA0PBZ
author_rank: Super Contributor
timestamp: March 23, 2017, 07:57:47 pm
content: Tried it on an MSOX3000:- it automatically shows the cursors when enabling the measurements- It sets the measuring point somewhere in the middle of the screen- It does show the correct min and max statisticsonlyif you scroll around in the waveform (see above)Picture:

author: alm
author_rank: Super Contributor
timestamp: March 24, 2017, 12:34:41 pm
content: Quote from: iBeta on March 23, 2017, 01:23:30 pmCalling people trying to help you stupid seems like a really smart way of making people willing to help you.What do the auto cursors show? I am guessing the measurement functions will only measure around the trigger point (or some place on the screen), and will calculate statistics across subsequent acquisitions, not multiple pulses in the same acquisition. Try restricting the measurement range to the other pulse widths with cursors and see what the measurement gives. To get the statistics you expect, try setting up the triggering so it will trigger on both the short and long pulses continuously, and see what the stats do.As expected, the user manual is completely useless in its description of measurements and statistics. It includes only textbook definitions of pulse parameters.

author: 2N3055
author_rank: Super Contributor
timestamp: March 24, 2017, 02:17:20 pm
content: It measures first event after trigger. Stats are not stats on one screen, but between consecutive screens (trigger events, buffer captures).. That is why I said to use auto cursors, which are showing you what it measures.