Rigol DS1074Z trigger issue - Page 1
Forum section: electronics / testgear

author: eyal
author_rank: Contributor
timestamp: April 11, 2018, 05:54:44 am
content: This did not happen to me before (for a few years) so it may be some setting I accidentally changed.Or it can be a problem with the DSO.I am running a trace where the device cycles every 6 seconds. A proper trace looks like this:However, it often fails to trigger, as in hereTo be sure, I changed the trigger level to 60mA but I still often getNote how it seems to trigger on the end of the waveform, and it missed the leading edge.I even introduced a hold-off of 10ms to ensure the end of the wave does not trigger but it did not help.Any help appreciated, and it is may very well be a stupid thing I am doing - just tell me anyway.BTW, the preview does not show the images, I hope they will show once it is posted...Regards

author: t_i_t_o
author_rank: Contributor
timestamp: April 11, 2018, 06:19:47 am
content: How is your trigger mode set Normal or Auto?If in Auto, considering your signal cycles each 6 seconds and the scale of your scope is now set to 6 seconds it means it will auto-trigger every 6 seconds, once triggered it will not re-trigger on the input signal.Try Normal or Single triggering mode and it should "fix" your problem.

author: eyal
author_rank: Contributor
timestamp: April 11, 2018, 07:08:32 am
content: As the images show the mode is "Sweep: Normal". Naturally, in Auto I would not expect alignment with a trigger level.cheers

author: JohnPen
author_rank: Regular Contributor
timestamp: April 11, 2018, 07:29:08 am
content: It might be worth limiting the B/W to 20 M as a fast spike might have an impact. You may of course already have that selected.

author: eyal
author_rank: Contributor
timestamp: April 11, 2018, 08:34:26 am
content: Yes, I have 20MHz BW limit.

author: dcac
author_rank: Frequent Contributor
timestamp: April 11, 2018, 09:09:06 am
content: Is it the same behaviour on the other channels 1-3?

author: eyal
author_rank: Contributor
timestamp: April 11, 2018, 12:54:52 pm
content: Tried ch3 with same results.ch2 same...

author: Fungus
author_rank: Super Contributor
timestamp: April 11, 2018, 01:40:10 pm
content: Not surprising, the trigger circuitry is separate and shared by all channels.If it used to work then there must be a setting you're missing somewhere.Try pressing "Auto".If that fails you could do a reset of all parameters and see if that fixes it.Press the magic button during power up:

author: eyal
author_rank: Contributor
timestamp: April 11, 2018, 01:48:41 pm
content: First time I hear about a "magic button" reset. I will keep it as a last resort...

author: eyal
author_rank: Contributor
timestamp: April 11, 2018, 03:53:15 pm
content: I still get unusual triggering. I now tried:- set "Utility - Settings - Power Set" to "Default". This restores system defaults on restart.- installed the latest firmware.- done a calibration pass.- finally, done a factory reset (magic button).I now seem to not get random triggers, but I do get some cases where the trigger fires on the trailing edge of the trace.Maybe it is time for bed to sleep on it.

author: CustomEngineerer
author_rank: Frequent Contributor
timestamp: April 12, 2018, 12:28:19 am
content: 10mS holdoff for an over 600mS wide pulse? I wouldn't expect that to have an effect for the pulse you show. Even the small dip at the beginning of the pulse looks to be 100mS after the start of the pulse.

author: alsetalokin4017
author_rank: Super Contributor
timestamp: April 12, 2018, 12:51:20 am
content: Quote from: eyal on April 11, 2018, 03:53:15 pmQuote from: CustomEngineerer on April 12, 2018, 12:28:19 amThis ^^. Try setting the Trigger Holdoff to something greater than the total pulse width, like 700 ms. This should prevent triggering on the TE of the trace. Also, even the rising edges of this pulse aren't all that fast. I'd also recommend boosting the sample rate (Acquire>Mem Depth up to 24M points) if possible.

author: eyal
author_rank: Contributor
timestamp: April 12, 2018, 02:25:16 am
content: oops, I mis-read holdoff as delay after the trigger condition passes. I now set it to 4s (the cycle varies between 550mms and 3.5s).I have now seen more cases where a trace has the trigger in a random place, e.g.And also still get some cases where the trigger is at the training edge. Holdoff is set to 4s (longer than the longest trace) so this should not happen.

author: Fungus
author_rank: Super Contributor
timestamp: April 12, 2018, 12:59:26 pm
content: Quote from: eyal on April 12, 2018, 02:25:16 amIs it always in the wrong place or just every now and again?Does it do that when you do a single capture? What happens if you change the horizontal timebase?You're not giving many clues.

author: rstofer
author_rank: Super Contributor
timestamp: April 12, 2018, 02:19:37 pm
content: How about the possibility that there is a very fast glitch that you just can't see at 200 ms/div? It could be that the scope is doing just fine.Maybe change the time/div to see what is actually triggering the scope.

author: Fungus
author_rank: Super Contributor
timestamp: April 12, 2018, 02:23:06 pm
content: Quote from: rstofer on April 12, 2018, 02:19:37 pmThat wouldn't explain this:(although a tiny spike in combination with a weird trigger holdoff could explain it)

author: 2N3055
author_rank: Super Contributor
timestamp: April 12, 2018, 07:21:29 pm
content: Enable Peak Detect acquisition mode... That will show you fast spikes....It may explain funny triggeringThere is also Trigger noise reject menu, in case there are fast spikes present...

author: StillTrying
author_rank: Super Contributor
timestamp: April 12, 2018, 08:00:52 pm
content: Trigger off the falling edge, ...and noise reject.