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RMS to DC scheme

Discussion in 'Electronic Basics' started by LemonPL, Oct 21, 2005.

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  1. LemonPL

    LemonPL Guest


    I need scheme of RMS to DC converter.
    What is important I can`t use integrated circuits (except opamps)
    in this approach.
    Thanks for your help

  2. John Larkin

    John Larkin Guest

    What other parts can you use?

    Who made this rule?

  3. ehsjr

    ehsjr Guest

  4. Kitchen Man

    Kitchen Man Guest

    This way to the Egress?
  5. Chris

    Chris Guest

    Hi, Lemon, or Lemone. You should have included your full name and the
    technical college or university you're attending, as well as the class
    and instructor. I'm sure your fellow students would be amused by your
    s.e.b. post. Your professor also might be interested, although I doubt
    he'd show his amusement in public.

    You know, if you need a free clue (and oh yes, you do), it's sometimes
    good to look through the existing literature rather than just re-invent
    the wheel. The early manufacturers of op amps (Analog Devices,
    Fairchild and National Semiconductor come to mind) published
    application notes in the 1970s to help users of their newfangled
    contraption, the IC op amp. A quick search of these sites using the
    phrase "True rms detector" should give you some help.

    But since it might actually involve work or thought to go to the
    National Semiconductor website and type in the search term "true rms
    detector", and actually scan a few of the links to see if they might
    have what you want (Frith forbid, you might actually learn something
    not connected directly with your homework assignment), retain the
    purity of your beautiful mind by holding your mouse and sliding it
    slowly until the pointer rests on the link below, to read National's
    LB-25, "True rms Detector". It shows a true rms detector circuit that
    uses five op amps, matched pair transistors, diodes and passive
    components. Once the pointer is resting over this link, press the
    mouse button.

    If your newsreader isn't capable of using text links, you'll have to
    copy the link, paste it to the address bar of your web browser, and
    then click the "Go" button to the right. If you need help with that,
    please post again if you can, and it's not too much work.

    Also, the link is in .pdf format. If you don't have the Adobe Acrobat
    Reader or it's equivalent (and I would guess you don't), please go to

    and download and install your free Adobe Acrobat Reader (use the icon
    labelled "Get Adobe Reader" on the left of the page). If you have
    trouble with this, you should contact somebody in the computer science
    department. For 20 zloty, you can usually buy a clue -- they'll be
    happy to give you a hand and set up your computer. Also, if you don't
    understand the app note, please use another 20 zloty note to have one
    of your classmates explain it to you. It's actually a pretty elegant
    combination of an op amp precision rectifier, multiplier, and divider.

    Good luck in your academic endeavors and career, and please call your
    Daddy to ask for a big pile of 20 zloty notes. I'd guess you're going
    to need them.
  6. Chris

    Chris Guest

  7. Bob Eldred

    Bob Eldred Guest

    Many of the posters have assumed that you are doing a homework problem for
    some class. But there are a number of questions that must be answered if you
    are serious about this. 1. What is the bandwidth? 2. What is the maximum
    frequency of operation. 3. What is the PAR, peak to average ratio expected.
    4. What is the voltage expected? 5. What is the dynamic range expected? 6.
    What are the waveshapes expected? 7. What precision is expected? 8. What
    speed of response is expected? 9. What transient response is required?

    The scheme picked depends on answers to these questions. For example, if you
    know the waveform is ALWAYS a sine wave the problem is simple and is just a
  8. Jasen Betts

    Jasen Betts Guest

    use a diode?
    hmm, isn't their forwards voltage/current curve exponential?

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