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mv to 5vdc isolation circuit?

Discussion in 'Electronic Design' started by Brad Woods, Oct 19, 2004.

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  1. Brad Woods

    Brad Woods Guest

    I'm trying to set up a data aquisition system and am looking for a circuit
    that will let me convert a 50mv DC signal from a current shunt to a 5v dc
    signal that can be input to a PLC. the measurement is on the high side of
    ground so it will need to provide isolation also. I've extensively searched
    but could not find good info on the net could anybody point me in the right
    direction .
    Thanks
     
  2. Why build what is available as an industrially hardened product?
    e.g.
    http://www.actionio.com/
     
  3. legg

    legg Guest

    Is the input to the PLC required to be ~linearly scaled or do you
    simply require a specific preset level indicator, with a tolerance?

    Wouldn't simple level translation suffice for either a linear or
    switched signal? Isolation could be an added complication, requiring
    interface power on the 50mV side.

    RL
     
  4. Tom Seim

    Tom Seim Guest

    Burr-Brown (TI) has self-contained isolation amps.
     
  5. Fred Bloggs

    Fred Bloggs Guest

    NO!!!!? REALLY?!
     
  6. Tom Seim

    Tom Seim Guest

    Yes, REALLY!! You ought to check them out, fredrook. Maybe you don't
    know who Burr-Brown is?
     
  7. Fred Bloggs

    Fred Bloggs Guest

    Nope- never heard of them. Is that some kind of clothing store chain?
    And why would they sell iso-amps?
     
  8. I have used a few of those. I used the ISO107 in a PCI card-based
    Brainwave Analyzer back in 1988. I had to provide Ul544 patient
    isolation to the instrument card. Unfortunately it wasn't very
    reliable over time. It was a great part while it lasted but its life
    span was only a few years.

    This device was a PC version of the brainwave analyzer that was
    invented by Dr. John Ertl, A PhD who pioneered the correlation between
    brainwave activity (Average processing speed) and intelligence. After
    a government study of 8,000 students, both black and white and was
    able to demonstrate his theory and create a substantial data base of
    EEG samples that were used in conjunction with thousands of other
    samples to provide a look up table by age and brain maturation. The
    EEG sample was processed using an algorithm created by Ertl. It was
    touted as the world's first electronic IQ test and it is in use still
    today in clinics around the world primarily for the detection of
    learning disorders in school aged children. Since the good doctor has
    passed away I have been tempted to resurrect my design and
    commercialize it. I can think of a few posters in here that I would
    love to take samples on!
     
  9. R Adsett

    R Adsett Guest

    Standard Industrial module from DataForth or Analog Devices
    http://www.dataforth.com/catalog/doc_generator.asp?doc_id=266

    Robert
     
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