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New Project -- Isolated Scope Probe

Discussion in 'Electronic Design' started by Jim Thompson, Dec 28, 2003.

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  1. Jim Thompson

    Jim Thompson Guest

    That's an interesting start. How about continuing this thread and
    making the isolated probe linear and accurate?

    ...Jim Thompson
  2. Luhan Monat

    Luhan Monat Guest

  3. James Meyer

    James Meyer Guest

    Using only 4 or fewer 2N3904's in a class A configuration.

  4. Jim Thompson

    Jim Thompson Guest


    ...Jim Thompson
  5. John Larkin

    John Larkin Guest

    And fast.

  6. Jim Thompson

    Jim Thompson Guest

    "fast" and "linear" may be mutually exclusive, or at least
    out-of-capability for most lurkers here.

    (That statement ought to be good enough to qualify as a troll :)

    John, What's your definition of "fast"?

    ...Jim Thompson
  7. Jim Thompson

    Jim Thompson Guest

    Refer to the "fsm*.jpg" and "Field Strength Meter" threads ;-)

    ...Jim Thompson
  8. Luhan Monat

    Luhan Monat Guest

    Great, any ideas are welcome, but even as-is, I have found this device
    extrodinarilly useful.

    If I want to know the exact signal voltage (rather than just its shape
    and timeing), I note the reading on the scope and then move the probe to
    my bench supply and duplicate the amplitude in DC. Then the power
    supply shows me the actual voltage level.
  9. Luhan Monat

    Luhan Monat Guest

    Why do I get the feeling this is some 'inside' joke????
  10. John Larkin

    John Larkin Guest

    Well, there aren't a lot of really fast floating signals around, like
    in the picosecond range. I'd think that something around 1 MHz would
    be handy for power supplies, power stages, stuff floating on the AC
    line, most switchers... things like that. Maybe 100 MHz would be about
    as far as it would be sensible to go for logic and more exotic stuff.

    There are integrated linear optoisolators good for 25 MHz or something
    like that. I don't think that extreme linearity or accuracy would be
    all that important, so a simple thingie should be possible. I guess
    highside power would be needed to make things work well... batteries
    or a (quiet) inverter.

    Group project?

  11. John Fields

    John Fields Guest


    1. There is no real repeatable so-called X1 or X10 capability for the
    thing unless each circuit it's connected to has exactly the same

    2. There is no X1, X10 correspondence between the output voltage and
    the position of the X1 - X10 switch with the same input voltage to
    the probe. For the PS2505 the CTR changes by about 2:1 for a 10:1
    variation in input current below 5mA, with the absolute CTR varying
    over about a 4:1 range from unit to unit.

    3. It's a _bad_ idea to force forward current into a watch battery and,
    I would suspect, a _very_ bad idea to subject it to the 100V reverse
    polarity half-sine it'll get across it from the ringing signal.

    4. There must be _something_ else... ;-)
  12. James Meyer

    James Meyer Guest

    Inside? By now it's the "Joke Heard 'Round the World". See almost any
    post by Paul Burridge. I can say that because Paul's a good natured guy. At
    least so far.

  13. How about two oscilloscope probes and subtraction mode? How far apart can
    ground and probe head get before it gets bad? How linear is the result of
    subtraction on, say, a Tek 475?

    What about tying the grounds together and letting them float?

    Bob Monsen
  14. James Meyer

    James Meyer Guest

    I can make a slow (100~200 Hz BW), DC accurate (1% or better), isolated
    to 500 Volts, probe with only three parts.

  15. mike

    mike Guest

    I've got a TEK A6902 I don't use.
    Make an offer.

    Return address is VALID.
    Bunch of stuff For Sale and Wanted at the link below.
    Toshiba & Compaq LiIon Batteries, Test Equipment
    Honda CB-125S $800 in PDX
    TEK Sampling Sweep Plugin and RM564
    Tek 2465 $800, ham radio, 30pS pulser
    Tektronix Concept Books, spot welding head...
  16. Joe Legris

    Joe Legris Guest

    He's also an asshole. You might say a self-made man.
  17. John Fields

    John Fields Guest

  18. John Fields

    John Fields Guest

  19. John Fields

    John Fields Guest

    Perhaps you should change your .sig to:

    Luhan Monat, "Luhan Don't Know Shit" At 'Yahoo' dot 'Com'
    "The future is not what it used to be."

  20. Roger Gt

    Roger Gt Guest

    Translation: The User Rejected Design!
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