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Thread: Wavy-line distortion (resonance?) with DT-40pro scanners at 18Kpps speed...

  1. #21
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    To do it right you need one of these:



    Bill
    Attached Thumbnails Attached Thumbnails DSA.jpg  


  2. #22
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    I made this video in 2015:
    https://youtu.be/Tj69w3QkDDk

    You'll note that this is a private (aka unlisted) video.

    It was made to compare our system to something developed by another company who had a 10mm scanning system and digital servo driver. From a performance standpoint, our system outperformed theirs in every way, but the good point about their system is that it is self-tuning whereas ours must be tuned manually.

    This video is kind of "Part 2". The "Part 1" video showed their system with our test patterns, and showed all of the things that was wrong with their system. I'm not showing Part 1 because it would reveal the name of the company, and it's not a point to publicly call them out...

    The purpose of the video was to start a discussion of a possible collaboration. By the way, the discussion went nowhere... Their system is still just as bad as it was back in 2015 although ours has continued to evolve (and we're literally working on self-tuning right now).

    Nevertheless, at time 10:20, you'll see the dynamic signal analyzer built into the system and how it works. This is what's really needed to set a notch filter (or two) set correctly. Doing it with a function generator and scope has some follies...

    By the way, in the video I mentioned that this servo driver could not drive the C506, but over the past year we've rectified that, with a new PD board for the C506 that is compatible with the Mach-DSP. Some PL folks may even have our C506 with Mach-DSP driver.

    Bill

  3. #23
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    Somewhat offtopic, but related to the c506... I helped some folk here shoehorn a scannermax set with older cambridge scanamps (using your component replacement docs)... Nicely done! Those are some really well designed scanners and the costs were surprisingly less than what the nicer (really nice?) chinese sets go for.

    Bill I've been meaning to jump on your forum and ask, whats the max speed I can clock XY2-100 into the Mach-DSP? Is it safe to go over 2Mhz? 20us a point (defined by the spec) is a hair bit slow for what I want.

  4. #24
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    Quote Originally Posted by yaddatrance View Post
    Bill I've been meaning to jump on your forum and ask, whats the max speed I can clock XY2-100 into the Mach-DSP? Is it safe to go over 2Mhz? 20us a point (defined by the spec) is a hair bit slow for what I want.
    XY2-100 standard is indeed 2MHz clock rate. It's 20-bits per coordinate. At 2MHz that's a 100kHz sample rate. (That's what the "2" and the "100" mean.) But that's 10uS per coordinate not 20uS.

    Theoretically Mach-DSP can accept coordinates with clock rate up to 25MHz, but I've never tested that...

    Bill

  5. #25
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    Quote Originally Posted by buffo View Post
    Sheesh! I'm conflicted here. On the one hand, I really want to try this. On the other hand, I'm nervous about blowing up someone else's scanners.
    No need to be conflicted, I'll volunteer a set of DT-40's for this. Let's do some destructive testing!

  6. #26
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    Cool

    Quote Originally Posted by araugh View Post
    No need to be conflicted, I'll volunteer a set of DT-40's for this. Let's do some destructive testing!
    Wow! Now that's an attitude I can get behind!

    After all, what's the worst that could happen, right?



    This ought to be fun!

    Adam

  7. #27
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    I could not afford the lovely SR785 Scannermax has, But a beat up HP 35660A is winging its way here as we speak. Supposedly it passes its self tests. One of those auctions where the guy thinks it will work, but does not want the hassle Fleabay will put him through if he charges the big bucks and it fails. Not to mention it is boat anchor sized and a Lexel 88 PSU has less mass. :-)
    ~
    So if the 35660 works,
    I think we're going to have a teachable moment (maybe an hour) at SELEM if my boss lets me escape. I'll try for Thursday-Friday presence.
    ~
    I'll bring a 6850 Amp, the scope, the arbitrary waveform generator, and some clone boards. The 6850 is the nearly indestructible teaching tool. The clones are bottled magic smoke waiting to happen. Call it the hard core galvo amp setup / scope tuning short course.
    ~
    We can also run 6800 with bad bearings, and 6800 with damaged coil, and 6800 with no mirror. We can also run some 6810s with various mirrors. I have a few Chinese notch boards.
    We'll set you up good Adam.
    ~
    Having a DSA laying around is a good thing when you work with mechanisms all day. I can justify it as a personal tool, for what I do at work.
    ~
    No Brad, You do not need your own Dynamic Signal Analysis system at SELEM......Leave the card in the wallet. '-)

    ~
    l'll bring the Turbotrack with 506s on it, too.


    Steve
    Last edited by mixedgas; 07-11-2018 at 07:48.
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  8. #28
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    Hi Steve,

    I hate to break it to you, but the 35660A does not have "swept sine" measurements. That's one reason why you could find them cheap on eBay. By comparison, the 35670A does have swept sine, as long as it has option 1D2 installed.

    There are also older ones, such as 3562 (that's what Cambridge had).

  9. #29
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    I've supposedly got the software for a form of swept sine in the "Periodic Chirp" setting ????
    ~
    I also have the option for an external sweeper, which I have.
    ~
    Its not going to be perfect then... I read the manual twice before purchasing,. I know it is going to be a bit of a Dog.
    Live and Learn.... Should still be a useful tool as a dual SA.

    Steve
    Last edited by mixedgas; 07-11-2018 at 10:08.
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  10. #30
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    Wow, this thread rapidly got way above my pay grade!

    Quote Originally Posted by araugh View Post
    No need to be conflicted, I'll volunteer a set of DT-40's for this. Let's do some destructive testing!
    Yeah, I was thinking the path of least resistance for the sets I have exhibiting this behavior was swapping out the mirrors for higher quality 3mm stock mirrors from Pangolin. Otherwise, avoiding 18Kpps scanning would be simple for most people, but I tend to use it for beam alignment, beamshows and glow in the dark art work, so this is how I tripped across the issue.

    That said, for those brave enough to attempt it or volunteer their galvos, bravo!

    Are we doing this at SELEM? If so, if its successful on the test patient, I'll bring three more sets to adjust.

    -David
    "Help, help, I'm being repressed!"

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