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I have a stepper motor that is controlled by PWM. I am trying to analyze the signal coming out of the controller on an oscilloscope. Ideally, I would like to capture, maybe 2 seconds of wave form so that I can see the exact signal being used to control the signal. I am using a Rigol DS1102E oscilloscope but and I am able to capture screen shots of the waveform, but not enough for me determine exactly how the controller is operating over an entire cycle. Does anyone know of a way to capture several waveforms so that I can see the entire signal over when it runs the stepper motor?

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  • \$\begingroup\$ You'll probably need an oscilloscope with a much deeper sample memory. \$\endgroup\$ Jul 17 '14 at 0:44
  • \$\begingroup\$ Use a logic analyzer instead. (e.g. pctestinstruments.com) \$\endgroup\$ Jul 17 '14 at 0:47
  • \$\begingroup\$ This oscilloscope definitely has a record function that seems to capture frames of waveforms, but I am unable to open the stored RCD file-type on my computer and it doesn't give me any way of freezing a frame and viewing it independently, at least as far as I know. As for the logic analyzer suggestion I just don't have one, so I'm kind of hoping there is a way to use this current oscilloscope if at all possible. \$\endgroup\$ Jul 17 '14 at 0:54
  • \$\begingroup\$ You might want to check to make sure you can't connect to the oscilloscope with some sort of serial connection, if you can, then Rigol might have some software you can use that will transmit the frames to your computer. \$\endgroup\$
    – Funkyguy
    Jul 17 '14 at 1:42
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    \$\begingroup\$ Have you tried downloading the software and drivers on the oscilloscope's product page? \$\endgroup\$
    – Evan
    Jul 17 '14 at 2:23
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I've got that 'scope. It sounds like you just need a bit more practice driving it. To capture a single frame set the 'scope up for "single" in the Trigger-> sweep menu.. right under "normal" and "auto". You'll then have to configure the trigger level and all such that you have a chance of triggering on what you want to see. (Sometimes you'll want to trigger on one signal and look at a different one.. or even two signals.. so you might have to use the external trigger input.) You may want to look at a lot of single shots to find the one that you want. Push the Run/Stop button to get another trace.

As far as getting waveforms into your computer. I usually just save a bitmap of the on screen picture. But you can also download a CVS file of the raw data, you've then got to have some other program to plot this data for you.

I hope that helps,

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  • \$\begingroup\$ Also, make sure you set the trigger hold off to something larger than one period of you PWM signal. \$\endgroup\$
    – RJR
    Aug 17 '14 at 7:09

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