Rigol DS1054Z Triggering Questions - Page 1
Forum section: electronics / testgear

author: DavidA
author_rank: Contributor
timestamp: August 22, 2017, 01:48:31 am
content: I posted thisherehowever I have a number of questions so it's probably worth its own thread.First of all, I am having some trouble with slope-based triggering. I have a periodic signal that has a negative slew rate of ~900 KV/sec (1 volt drop over ~1.116 us) and when I'm using the "trigger when the negative slope time of the input signal is greater than the specified time" mode it triggers at a setting of 8.00 ns (125 MV/sec) but fails to trigger at all at the next value up, which is 9.00 ns. From my understanding based on the User Guide, it should trigger all the way up to about 1 us.Then I moved the T1 and T2 levels down 0.5V (nearer the mid-point of the slope) and this seems to trigger more reliably, up to about 800 ns of minimum slope time, so that's much better (second image). Seems that the top voltage threshold needs to be about half a volt below the maximum value to trigger properly. So depending on the trigger levels, close to maximum signal causes very fast slew rates (1V over 1.1 ns) to trigger even at 1V > 800 ns. Not sure what's going on here.The third and fourth images show a weird effect I'm seeing in "Normal" sweep mode. I've seen it with both slope-trigger and edge-trigger. What's going on here? It's as if several traces have been drawn at once, during a single trigger. I have "Min" persistence set, so it's not that. I don't see this effect with Single or Auto sweep mode, and about half the time the trigger is a single trace. With the fourth image, I only see this for 1.00 us/div or less.I'm using v00.04.04.SP3 with Board Version 0.1.4, unlocked.

author: DavidA
author_rank: Contributor
timestamp: August 22, 2017, 02:18:45 am
content: Here's another odd example: the scope reports that the slope is 902MV/s (and from cursor measurements this seems to be about right) but the trigger condition is "> 15.0 ns" which at BY-AY=1.6V should be triggering for a rate less than 107MV/s. However at the trigger point, the signal is clearly much, much faster than this threshold, yet it triggered.

author: DavidA
author_rank: Contributor
timestamp: August 22, 2017, 03:01:26 am
content: A couple of additional questions that I haven't been able to find answers here or in the User Guide for:Is there a way to move the Cursor box (that shows AX, AY, BX, etc) when in Manual Mode? It sits in the top left hand corner and sometimes I'd prefer it was in the bottom half somewhere.Is there a way to count the number of trigger events (other than using Measure>Counter and counting pulses on the Trigger Out BNC port on the back with a spare channel). For example, I want to leave the scope unattended for a period of time and count the number of triggers over, say, a 12 hour period (to get a feel for how commonly a triggering situation arises).

author: zbyr
author_rank: Contributor
timestamp: August 23, 2017, 12:03:44 pm
content: Quote from: DavidA on August 22, 2017, 01:48:31 amThis is normal, watch this video.https://youtu.be/ta096oBzSacQuote from: DavidA on August 22, 2017, 02:18:45 amThis one is easy to explain, trigger sampling rate is same as current oscilloscope sampling rate, but measurement and cursors are based on points on screen, which are 1200 points max, so you must zoom in to measure it precisely.edit: sorry i didn't notice that you have 5ns/div and can't zoom in furtherl, but signal which you try to trigger is at limits of this scope, so it gets confused, even if your digital sampling is 1GSPS -> so 1ns between two points, your analog bandwith is only 100MHz (if hacked, if not it's even worse), so rise/fall time is limitted by front end, in thread "new rigol..." people made measurements of max rise/fall time in this scope, you can look at these, also in 3ns rise time your scope got only 3 points to make a decision...Quote from: DavidA on August 22, 2017, 03:01:26 amNo.Quote from: DavidA on August 22, 2017, 03:01:26 amYou can do it indirectly, using any measurement with statistic on in difference mode, there is Cnt , it is not precise but only option without trig out, it's cheap scope and lack some features...Also use full screen on scope for waveform, because it's digital scope, half screen = half resolution of adc.

author: DavidA
author_rank: Contributor
timestamp: August 23, 2017, 09:50:17 pm
content: QuoteThanks, that was a useful video. So if I understand correctly, the scope is deliberately overlaying the traces onto a single frame buffer (for display) to emulate the luminous persistence of an analog scope (with zero hold time). I.e. if the DSO triggers multiple times between LCD screen refreshes, it will combine the multiple triggers into a single display frame (because it can't show them all fast enough). That's a useful way to know that changing the Holdoff might be required.QuoteI'm new todigitalscopes so I hadn't realised until very recently that measurements are made based on the displayed data, so that makes sense. I tried again with a slower signal (hundreds of nanoseconds rise time) and it seems to behave as expected.It's a pity that the Cursor box can't be moved but it's easy enough to dismiss it or move the waveform around if it really is in the way.If Rigol are reading, it would be useful to have a softkey that simply toggles it between two or four preset locations...QuoteSorry, I don't see "Cnt" in the Statistics window - only "Cur", "Avg", "Max" and "Min" - am I looking in the wrong place? See image.QuoteThanks for the tip!

author: CustomEngineerer
author_rank: Frequent Contributor
timestamp: August 23, 2017, 10:44:30 pm
content: After you turn statistics on a new menu item should appear called Mode. This defaults to Extremum which gives you Cur, Avg, Min and Max. If you change it to Difference, the statistics will be Cur, Avg, Dev and Cnt.

author: CustomEngineerer
author_rank: Frequent Contributor
timestamp: August 23, 2017, 10:47:09 pm
content: Quote from: DavidA on August 23, 2017, 09:50:17 pmCompletely agree with this. If Rigol is paying attention also please add to the DS2000A series (realize not likely, but would be nice).

author: zbyr
author_rank: Contributor
timestamp: August 24, 2017, 12:45:39 am
content: Quote from: CustomEngineerer on August 23, 2017, 10:44:30 pmYup, that's the way, but it works only with slow time base (tens of ms because measurements are slow, they can be much slower than trigger, but cannot be faster). You could make a simply pulse counter with microcontroler if you want count faster events, cheap 8bit mcu will do the job (max update rate is 30k/s).

author: DavidA
author_rank: Contributor
timestamp: August 24, 2017, 03:12:50 am
content: Quote from: CustomEngineerer on August 23, 2017, 10:44:30 pmAh, that works fairly well for my situation. I can now leave it running and come back later to see if it has triggered just once or many times, giving me some idea of how frequently a certain (and hopefully rare) situation arises. Thank you.