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oscilloscope calibration

Discussion in 'Electronic Basics' started by Mike, Dec 13, 2004.

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  1. Mike

    Mike Guest

    Hi there,

    Does anybody know of a place somewhere in southern NJ (or closeby area) that
    calibrates oscilloscopes? How much does this usually cost? I tried searching
    for some places but the closest place is in philly, pa.

  2. Bob Masta

    Bob Masta Guest

    I assume you are talking about the voltage and frequency
    ranges. If so, you can probably make your own calibrator.
    Many scopes have a simple calibrator built in, just a square
    wave at 1 volt and 1 kHz or some such. You can use a
    crystal and some frequency dividers to get a whole
    range of frequencies. Use them to chop the output of a
    precision voltage reference. You can also make a
    precision divider by matching a series of resistors, or you
    can use digital PWM to produce a high-frequency pulse
    train with a duty cycle that you can set in steps.

    Not only is this a good project, it's a handy thing to have
    around the lab.

    Best regards,

    Bob Masta

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
  3. Mike

    Mike Guest

    Hi Bob,

    That definitely does sound like a good project. If I could do it myself, I'd
    rather not pay someone else. One of the sellers I came across says that the
    frequency of the calibration is 975mhz, and the book actually calls it a
    1khz signal. Is that true? Is it bad if the person modifies the internal
    circuitry to reflect closer to 1khz?

    I have zero experience with scopes... please excuse the ignorance.


    I'm pretty familiar with voltage dividers, series, and parallel circuits, so
    I'm sure it's something I can handle. Also, I came across a seller on ebay
    that retrofitted the scopes crystal to
  4. CFoley1064

    CFoley1064 Guest

    Subject: oscilloscope calibration
    Hi, Mike. You might want to call the local junior college or trade school and
    ask them where they go for calibration services.

    Good luck
  5. Mike

    Mike Guest

    Great idea... thanks.
  6. I don't think the built-in scope calibrators should be relied on too
    much for frequency. Their primary purpose is to provide a nice square
    wave that you can use when setting the probe compensation on a 10X

    Peter Bennett, VE7CEI
    peterbb4 (at)
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  7. Bob Masta

    Bob Masta Guest

    I'm not sure what device the 975 Hz (probably not milliHertz) refers
    to. I don't advise messing with the internal circuitry of the scope,
    but of course if you build your own it will be as accurate as the
    reference crystal you use. Since scopes are usually just for visual
    comparisons (unless you have one of those fancy ones with
    counter circuitry built in), you only need to make is as good as you
    can resolve on the scope face. The raw accuracy of any crystal
    you find will probably be much better than that.

    Best regards,

    Bob Masta

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
  8. Mike

    Mike Guest

    Yes, I meant 975hz -- doh.

    Thanks for the input. I wouldn't think of modifying any of the scope
    circuitry; I was just baffled by someone else doing it.

  9. Guest

  10. Mike

    Mike Guest

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