Help with triggering on DSO to check changeover time on UPS - Page 1
Forum section: electronics / beginners

author: PTR_1275
author_rank: Frequent Contributor
timestamp: February 06, 2015, 01:37:05 pm
content: Hi guys / gals,Needing a bit of help with this one. I have a battery backup UPS and am curious to see what the changeover time is between mains power and battery backup. I'm pretty new to scopes and I can't think how I would trigger it.I am well aware of the issues with connecting the scope up to mains power directly and I have never done that. I use a small transformer with a 12vac isolated output as a isolation transformer (That was what I had lying around at the time) I use it for monitoring the clipping and distortion on inverter waveforms with no problems. I don't need critical voltage readings so it being a odd ratio doesn't bother me.As for the triggering, because I am trying to trigger at the absence of a waveform, I don't know how to do it.The scope I have is a rigol 1054z, not sure what other info you will need to help me, but please ask what you need to know and I will get the info to you.Thanks in advance and I look forward to hearing you advice-Chris

author: dave_k
author_rank: Frequent Contributor
timestamp: February 06, 2015, 01:52:44 pm
content: Not sure if the 1054z is capable of doing this, but if you can put it into ROLL mode and start running it shortly before you do the switch-over, and stop it shortly after. You'll then be able to scroll back and view the event, set markers to measure any switching times, etc..

author: nfmax
author_rank: Super Contributor
timestamp: February 06, 2015, 02:22:24 pm
content: Set the scope up to trigger in 'normal' mode from the input mains signal on one channel (via a transformer, for safety's sake) and set the trigger level to somewhere above 50% up the positive half cycle. Now switch off the mains, and the trigger will go away - in 'normal' mode this causes the screen to stop updating. Use the other channel to monitor the output of the UPS (again via a transformer, please)

author: ConKbot
author_rank: Super Contributor
timestamp: February 06, 2015, 07:18:36 pm
content: Trigger on rising or falling edge with a holdoff longer than 20ms (i.e. 25 or so) There has to be no trigger events (edge crossings in edge mode) for more than 25ms. So in normal operation, there will be a trigger every 20ms in 50Hz land and 16.6 ms in 60Hz land. If 25ms elapses from the last trigger event, the scope re-arms, and triggers on the next edge.

author: PTR_1275
author_rank: Frequent Contributor
timestamp: February 07, 2015, 08:36:19 am
content: Awesome for the advice guys. I was playing around on the bench briefly and I got the holdoff trigger to work. The idea of a second input and triggering it that way sounds good aswell, I will try that way also just to see for myself.I couldn't find a roll function on the scope but I will look through the manual and investigate that option too for my knowledge.I've bought 2 x 24vac transformers that I'm going to build into a box with terminal posts to make it easier in the future. That will also give me more accurate voltage measurements as it is essentially 10:1.I will play around and learn from here.-Chris