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Finally got me a 'scope - Have some questions
- Thread starter Supercap2F
- Start date
Supercap2F
- Mar 22, 2014
- 550
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- Mar 22, 2014
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- 550
Supercap2F
- Mar 22, 2014
- 550
- Joined
- Mar 22, 2014
- Messages
- 550
Today I was trying to learn more about op-amps, so I built a "phase shift oscillator" that is supposed to generate a sine wave. So I hooked it up to my scope and sure enough, it made a pretty nice looking 1kHz sine wave. Here's a photo at a timebase of 0.2mS:
But when I changed the time base to 0.5mS here's what it looked like:
I couldn't get it to be sharp like the trace on the first photo. The third photo is after adjusting the trigger a little, but if I adjust it anymore the trace will disappear. On pretty much all of the other timebases, I can get a good sharp trace like the first photo.
Do you guys think it's anything to be worried about?
Thanks very much!
Dan
But when I changed the time base to 0.5mS here's what it looked like:
I couldn't get it to be sharp like the trace on the first photo. The third photo is after adjusting the trigger a little, but if I adjust it anymore the trace will disappear. On pretty much all of the other timebases, I can get a good sharp trace like the first photo.
Do you guys think it's anything to be worried about?
Thanks very much!
Dan
- Joined
- Jan 21, 2010
- Messages
- 25,510
I think you may be learning about triggering
It's not immediately obvious what your trigger settings are but the second trace is indicative of the scope triggering at two places in the signal. What happens is that every sweep picks a different trigger point so you get multiple copies of the waveform with different phase relationships (or delays).
When you adjust the trigger, you may be either adjusting the level or the hold off.
If the former, the trace will disappear when the trigger level is outside the waveform. With this adjustment the phase relationship of the traces will change with the trigger level.
If the latter, you are forcing the scope to insert a delay at the end of each sweep before it teams the trigger. If carefully adjusted this can mean that you always trigger at the same point.
The other major consideration is how the trigger is set. Along with the level you normally can adjust it to trigger on either a rising or falling signal. This I'd fine, but noise on the signal can change a rising edge to a falling edge if the signal is shore enough or the noise large enough.
Probably not the most useful answer here but it should give you things to think about.
And hopefully not too many autocorrect errors!
It's not immediately obvious what your trigger settings are but the second trace is indicative of the scope triggering at two places in the signal. What happens is that every sweep picks a different trigger point so you get multiple copies of the waveform with different phase relationships (or delays).
When you adjust the trigger, you may be either adjusting the level or the hold off.
If the former, the trace will disappear when the trigger level is outside the waveform. With this adjustment the phase relationship of the traces will change with the trigger level.
If the latter, you are forcing the scope to insert a delay at the end of each sweep before it teams the trigger. If carefully adjusted this can mean that you always trigger at the same point.
The other major consideration is how the trigger is set. Along with the level you normally can adjust it to trigger on either a rising or falling signal. This I'd fine, but noise on the signal can change a rising edge to a falling edge if the signal is shore enough or the noise large enough.
Probably not the most useful answer here but it should give you things to think about.
And hopefully not too many autocorrect errors!
Supercap2F
- Mar 22, 2014
- 550
- Joined
- Mar 22, 2014
- Messages
- 550
Ahh, yes I forgot about the hold off control! I hooked up the sine wave again and with a little adjustment of the hold off, it now looks perfect!
Also, I measured a square wave that before had been glitching on the screen, and with some more adjustment of the hold off, it looked perfect too!
I think I also now understand how the trigger works a lot better too! Thanks Steve!
Dan
Also, I measured a square wave that before had been glitching on the screen, and with some more adjustment of the hold off, it looked perfect too!
I think I also now understand how the trigger works a lot better too! Thanks Steve!
Dan
