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I just ebayed an old oscilloscope so i could continue work on my brushless motor controller, but i am currently having trouble getting it to display the trace i require (and have had previously on other oscilloscopes)
Registered Member #142
Joined: Sat Feb 11 2006, 01:19PM
Location:
Posts: 102
How about giving us some info we can get our teeth into. What kind of scope. Frequency of your waveform. What you have tried. What happens if you generate a square wave of the same freq and amplitude using some other type of circuit, then scope that? I have an old scope with a HF stability knob I can twiddle when the waveform is acting up.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
I can't conceive of any triggering defect that could transform the top trace into the bottom one. Are you sure your motor controller circuit is working properly?
Registered Member #618
Joined: Sat Mar 31 2007, 04:15AM
Location: Us-Great Lakes
Posts: 628
Could perhaps be that the newly acquired scope has a slightly different sampling rate and is having a difficult time making it look like the top trace.
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445
Are you sure that you didn't somehow turn on a second trace?
Failing that, I would venture that the motor controller has some type of logic error and is outputting high during the 'off' times a sizable fraction of the time. Try putting the scope in single shot mode and manually trigger a few times to confirm/deny that this is happening.
Registered Member #3215
Joined: Sun Sept 19 2010, 08:42PM
Location:
Posts: 780
please, could you send a picture of the scope facade so we can devise on your settings?
I think it is a triggering problem
if your triggering behaves like that it can be due to triggering on the wrong edge of the pulse, or bad triggering level (usually you pull the pot and rotate it to adjust the level)
could also be trigger coupling which must in that case be DC
another solution would be external triggering on your clock source (it would be synced with the output normally)
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How to get oscilloscope to display the desired trace?
