Uses and help with a dual sweep oscilloscope - Page 1
Forum section: electronics / general

author: aXit
author_rank: Contributor
timestamp: October 11, 2010, 11:29:51 am
content: Hey guys, I just bought my first scope. 40MHz ebay one, everything you would expect for about $100, and in very very good condition.But it does have one feature that I haven't really figured out yet, dual sweep.As you can see it has a split knob for the time/div setting, and a selector panel above it for A/B/TRIG'D, all are push in, push out switches. TRIG'D seems to have minimal effect on the actual triggering, in that without it, it it stable, and with it a wisp of the rising/falling edge becomes visible. But the A/B confuses me greatly. Depressing A seems to have no effect. Depressing B seems to make the dial for B actually set the time/div, and the dial for A manually override the interval for the start of a triggered sweep (to give an example, you could set B for a certain time/div and then use A to change the amount of time the scope waits for the next triggered sweep, so you could have a single waveform on the screen, or you could have a sweep happen only a few times a second). Depressing both A and B at the same time makes a section of the full sweep (time/div set by A) double the brightness, the length of this brighter section being set by A. EDIT: ok, by clicking A after highlighting a certain section, you can go to viewing just that highlighted part on the full screen, ok found one useThat's another photo from the ebay auction itself, if I can take any pics of specific things that might help with explaining this, just say.So I'm a little confused as to if I'm using these properly, or if they have any inherent use at all. Any info on this system, or if your scope has a similar system and you could share some info would be great.Thanks, aXit.

author: DJPhil
author_rank: Frequent Contributor
timestamp: October 11, 2010, 01:55:24 pm
content: I'm not quite awesome enough to tell what scope that is from the instrument panel, but if I could I'd checkBAMAfor a manual for you. That might help the most.The time/division knob controls the delayed sweep. The A channel is for the delay window size, which is limited to a maximum of 1ms, and the B channel is the main sweep you can set to anything. The TV V and TV H printed there are for reference, they denote the signal periods used for vertical and horizontal analog television signals. The coarse and fine delay knob will set the length of time after B triggers before the A window is displayed.The trigger switches probably operate as follows:Normal (B pushed in)Default trigger, normal operationDelayed (A pressed in)Trigger B then wait A and show the waveform, this is your main zoomed in delayed sweep mode. Useful for all sorts of things (see here). Think of triggering on the clock of a multiplexed display (or lcd screen) and delaying a portion of the clock to see if a particular segment (or line, or pixel) was lit. It's a rough concept to self teach, but once it clicks you'll be hungry to use it on everything!Delayed with A intensifying B (A and B pressed in)This shows you the default B and allows you to see where A is by making the trace brighter. You should be able to adjust the A sweep period and delay to select the window you'll see if you pop the B button back out for Delayed mode.B TRIG'DThis is what you push in to have the main B sweep trigger on an external signal. This has a million uses, but if you think about combining it with delayed sweep you'll see that you can accurately trigger on any analog TV signal and examine any part of it. This scope seems designed to the task. It's even got a TV coupling option!All in all, delayed sweep is an awesome tool, and very worth the two days I spent beating my head on the desk learning what it was.Hope that helps.

author: aXit
author_rank: Contributor
timestamp: October 11, 2010, 10:40:58 pm
content: It does help, very much, thanks!I think I have it the wrong way around though, A pushed in is "normal" mode. In dual sweep mode, the length of the highlighted section is controlled by B and unpressing A takes you into that highlighted section. The "A INT" makes sense now, means that A is the initial sweep, and B is the delayed sweep. And yeah, B knob only goes up to .5ms.I hadn't thought to use the delay knobs in dual sweep mode, and yes, moving them changes the location of the highlighted section.Thanks a lot for the help, it seems I have more experimenting to doaXit

author: DJPhil
author_rank: Frequent Contributor
timestamp: October 11, 2010, 11:10:42 pm
content: After a good night's sleep I realize I probably should have just likened it to a horizontal zoom. I was bound to mess up some part or another but you've got it in spite of me.