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Function generators (again)

Discussion in 'Electronic Design' started by George Herold, Jan 22, 2013.

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  1. We need a function generator (FG) to recommend to customers for
    various experiments. We were reselling the protek 8003, but I found
    out today that protek is no more! So I’m back searching.
    We’d like to just have one function generator that could ‘cover’ a few
    different experiments.
    For one we need Sine waves from 0.5 to 2 Hz, with at least 10mHz
    resolution.
    (1 mHz would be nicer.) (This seems to eliminate a lot of the low end
    FG’s out there.)

    The other function would be sine wave sweeps and bursts, frequencies
    from hundreds of kHz to 5 MHz at a minimum.

    Oh price, The protek was selling for ~$300. Something near that
    would be nice. lets say no more than $1k.

    So I’ve been through the usual suspects, Rigol, B&K, Instek, Fluke.
    Tek, Agilent.

    The only one that fits the bill is the Rigol DG1022. I seem to recall
    someone having issues trying to program it. I don’t really need that
    function for our customers. But it would be nice for my own use.
    Any idea if Rigol has fixed that?

    Any other candidates?

    Thanks
    George H.
     
  2. Joerg

    Joerg Guest

    I have the Mastech SFG-2120. The first one had major issues but after
    they sent me a new one it's fine. However, it seems to be permanently
    out of stock.
     
  3. Thanks, I'm not sure analog will work for the low frequency
    application.

    There we are looking at the resonance of a torsional harmonic
    oscillator.
    Freq ~ 1 Hz and Q's of 0.5 to 100 (or more) So being able to step
    through the resonance digitally is very nice.

    The Rigol looks sharp
    http://www.rigolna.com/products/waveform-generators/dg1000/dg1022/

    (At least they don't look to be going away unlike protek.)

    George H.
     
  4. Nico Coesel

    Nico Coesel Guest

    The Siglent SDG1005 comes to mind. Lecroy sells these under their own
    brand name.
     
  5. Hnmm that's interesting thanks. It looks a bit like the Atten
    ATF20B.. which was panned here,
    http://www.eevblog.com/forum/reviews/atten-atf20b-teardown/

    Seems like there are zillions of FG's.

    George H.
     
  6. Guest

    can it be a pc based one?

    -Lasse
     
  7. Jamie

    Jamie Guest

    I have a DG1022 and it works very well. The programming issue is the
    PC software. I loaded it, it seems to work, just not very glamorous as
    some may expect.

    My latest use of this gen was a QAM and QPM experiment, where I used
    both channels to test some application theories.

    I see they're still lots of venders out there offering them but I
    wouldn't pay over $400. I just don't think they are worth over that.


    Jamie
     
  8. Nico Coesel

    Nico Coesel Guest

  9. Thanks Jamie, The dg1022 lists for $379 on the rigol web site.
    (If we buy in bulk (25-50) we may be able to wrangle a discount.)
    I figure we'll order one to play with,
    Rigol seems like 'brand name' now.
    Say what's the shortest pulse it will output?

    George H.
     
  10. Hmm that's an interesting question. I don't want to be in the postion
    of helping customers to get the pc interface working.

    What do you have in mind? A usb thing with some bnc connectors might
    work.

    George H.
     
  11. OK thanks.

    It's like a jungle out there for low end test gear.
    George H.
     
  12. Joerg

    Joerg Guest

    If you go that route make sure that the generators is totally,
    positively, one-hundred percent isolated at the USB link. Else all hell
    can break loose and you'll be in the business of noise fixing. "Hey,
    George, they installed this new elevator and now ..."

    I think Velleman has some USB-based generators that are isolated but not
    all of them are. You'll have to go through and check the specs.

    Other than that Lasse's idea is a good one because it can get you back
    into your previous old $300 price range.
     
  13. Jamie

    Jamie Guest

    Hmmm, shortest pulse..

    Pulse width are in the range of
    500uHz up to 3Mhz

    But in order to generate a standing pulse you need
    to define the other parameters too, like Delays, levels,
    source etc.
    http://www.rigol.com/download/Oversea/DG/User_guide/DG1022_UserGuide_EN.pdftrigger


    Scroll down a bit but don't miss the back panel options while you're
    scrolling :)

    Jamie
     
  14. Thanks Joerg, I must admit a preference for a self contained box.
    But some customers may like a computer thing.

    The rigol for $379 seems like a decent deal. We use to buy the
    proteks for $300... (and have to resell them for more... obviously)
    There were a bit dicey. (I wonder if the crappy fans took them down?)

    Any price increase will be passed on, and the rigol may be better
    value for the money.

    Hey at 20MHz the rigol can replace the SG9000,

    http://shop.vetcosurplus.com/catalog/product_info.php?products_id=7455
    (we don't pay that much for them.)
    that we resell with optical pumping (OP).
    The OP uses a fixed frequency RF and sweeps the B-field,
    but it's sometimes easier for students to understand a fixed field and
    swept frequency.

    George H.
     
  15. Uwe Hercksen

    Uwe Hercksen Guest

    Hello,

    what about a generator with DDS (digital direct synthesis)? They are
    very good for low frequencies and good resolution.

    Bye
     
  16. Rick

    Rick Guest

    You might take a look at this.
    http://www.ebay.com/itm/8MHz-DDS-Fu...ultDomain_0&hash=item2c66722160#ht_5580wt_918

    It does not have an enclosure but works well. I have used mine for two
    years with no problems. There are several with different specs and outputs
    for as low as $8.

    Rick
     
  17. That's interesting. How the 'bleep' can they make it so cheaply?

    George H.
     
  18. Rick

    Rick Guest

    It remembers last settings.

    Rick
     
  19. Rick

    Rick Guest

    That's interesting. How the 'bleep' can they make it so cheaply?

    George H.

    I used to buy a relay from a New York company for $2.44 in 100's. They
    pissed me off so I started looking in China for relays. I now buy the SAME
    one for 63 cents with free shipping. Where is the fat?

    Rick
     
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