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oscilloscope probes (ins and outs)?

Discussion in 'Electronic Design' started by Sam Kaan, Dec 31, 2003.

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  1. Sam Kaan

    Sam Kaan Guest

    What is really the internals of these oscilloscope probes?
    Are they basically a circuit that steps down your input voltage to a very
    tiny amount safe enough for the delicate circuitry of the scope to handle?

    By the way what are some recommended books for a beginners to oscilloscopes?
     
  2. Jem Berkes

    Jem Berkes Guest

    What is really the internals of these oscilloscope probes?
    (This is just a guess) but the oscilloscopes I've seen show a high input
    impedence, like > 20 Mohms so I'm guessing that there's pretty much
    electrical isolation provided by something like a FET.
     
  3. oscilloscopes?

    sci.electronics.equipment is an appropriate group for discussion of test
    equipment and accessories.

    Probe internals vary tremendously depending on the type of probe. They
    could be anything from a straight wire to... well, anything. A typical 10x
    passive probe contains a series resistor of around 9MEG, and then a trimmer
    capacitor at the scope end.

    Scope inputs are generally not "delicate", at least for a reasonable quality
    scope. Your scope manual will tell you what its limitations are; often they
    can handle up to 200V or so, depending on sensitivity range.

    Old Tektronix manuals are a great way to learn about how to use a scope and
    how scopes work. I believe they also have some books on using scopes, but I
    don't remember the reference offhand; ask on sci.electronics.equipment.
     
  4. The typical high speed probe contains a 9 meg resistor that in
    combination with the typical 1 meg input resistance of the scope forms
    a 10 to 1 voltage divider. They also have a small adjustable
    capacitor across the 9 megs to trim the high frequency division
    against the input capacitance of the scope and the cable. There are
    also 100 to 1 versions for high voltage work.
     
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