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sample and hold chips

Discussion in 'Electronic Components' started by Rune Christensen, Aug 30, 2004.

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  1. Hello

    I'm looking for sample and hold chips.

    I need to build a 6 channel data acquisition system and the 6 channels need
    to be simultaneously sampled.

    Thanks
    Rune
     
  2. mike

    mike Guest

    You wouldn't need to do it simultaneously unless the signals were
    changing. That begs the question, "how fast are they changing?"

    It might be helpful to state your requirements for aperture time,
    how long you need to hold at what accuracy, source impedance?
    mike

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  3. The sampling frequency is 12800 Hz 12bits and the signals I'm going to
    measure on is a three phase system with voltage and current sensors. In
    order not to loose any phase information of the signals I need to sample all
    6 channels simultaneously.

    I have looked at two chips LF398 and SMP04.

    It's part of the final project before I can get my degree. At the university
    they have a similar project where they use the SMP04.

    The chips need to be cheap and in dip package.

    Rune Christensen
     
  4. mike

    mike Guest

    Ok, that's good but you didn't answer my questions.
    Look up the specs on the chips you've described and figure out how to
    translate your system requirements into numbers that appear on spec
    sheets. This is your senior project, not mine.

    You seem to be falling into the same trap many of us have.
    There is no such thing as simultaneously. You can't just measure
    everything arbitrarily accurately and do the math.
    Engineering is the art of figuring out how sloppy the system can be
    and still get the job done.

    I'm making the rash assumption that if it's three phase, it's a motor
    or something similar. System noise is likely to swamp what you're
    trying to measure. I'd worry a lot about that. 12-bits of resolution
    on something that might have 50% noise spikes may be overkill.

    BTW, if it's really a sine wave of known or measurable frequency, you
    may be able to use one a/d and correct for the time skew in the
    measurements. Is there some reason you'd expect one phase to be
    radically different from the others? Think about how many things you
    can NOT measure and still get the job done.
    mike

    --
    Return address is VALID.
    Wanted, 12.1" LCD for Gateway Solo 5300. Samsung LT121SU-121
    Bunch of stuff For Sale and Wanted at the link below.
    Compaq Aero floppy,ram,battery.
    MINT HP-41CV, 2-METER AMPS, 200CH SCANNER
    http://www.geocities.com/SiliconValley/Monitor/4710/
     
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