Scope questions

Discussion in 'General Electronics Chat' started by maxpower097, Jan 11, 2010.

  1. maxpower097

    Thread Starter Well-Known Member

    Feb 20, 2009
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    Hey guys I'm a hobbiest/newbie pro with microcontrollers and don't really do anything crazy hard. Pretty much just mess around with 8bit - 32bit mcu's. I'm definately getting to the point where I need a scope. Do you think one of the 100mhz USB scopes would work for my needs or should I be looking at an older professional bench scope? I've seen some cheaper scopes for $100 on ebay. I'm sure these would be slow like 20mhz - 40mhz but do you think these would fit my needs for a while till I grew out of it and moved past MCU's?
    Thanks
     
  2. retched

    AAC Fanatic!

    Dec 5, 2009
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  3. sceadwian

    New Member

    Jun 1, 2009
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    I still haven't outgrown the 500khz analog scope I got off ebay for 30 bucks (delivered) It's a rackmount boat anchor, but it has a maximum .1mv per division, the time base is accurate and it acts finely as a high speed analog multimeter.

    20mhz is fine for most work, and be wary of mhz of bandwidth vs samples per second for a digital scope, as the bare minimum frequency you get get out of a 100msps digital scope is a 50mhz signal. Typically de-rating for samples to bandwidth is done at 4 to 1, so for a 100 mega sample per second scope the bandwidth should be considered 25mhz. Higher if you need actual precision.

    Also the maximum bandwidth on most scopes is almost always listed for a 10X probe, not a 1X one.

    Link the scope you're looking at.

    I would highly recommend spending about a month trying to find a good deal on a cheap boat anchor from e-bay, even if it's dead on arival the components you can get from it internally are worth more than the auction cost and shipping combined.
     
  4. maxpower097

    Thread Starter Well-Known Member

    Feb 20, 2009
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    hmmmmm. very good advise. Let me read that link and do a lil more research and I'll post what I'm looking at.
     
  5. bitrex

    Member

    Dec 13, 2009
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    I managed to pick up a 50 Mhz Kikusui oscilloscope that still had a valid calibration on it from Ebay for $50 a little while ago. It's a really solid scope and works great with two 100 Mhz 10x probes I picked up in another auction. You might want to check out that brand as they don't have the name recognition that Tek or HP does, and are very reasonably priced.
     
  6. VoodooMojo

    Active Member

    Nov 28, 2009
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    10 and 20 MHz are the speeds available for the 16F877 microcontroller.
    50 MHz is the standard for both the SX-18 and SX-28 microcontrollers.
    It depends what speeds you are working with to view clock frequencies.
     
  7. sceadwian

    New Member

    Jun 1, 2009
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    16F at 10-20mhz or SX whatever at 50mhz doesn't matter, what's of interst is the actual signals you're viewing. The input or output frequencies of a micro controller are rarely even a significant portion of the main clock speed. It is almost never required to have to directly observe the clock frequency of a micro controller as this would entail tapping the crystal directly, which would alter it's frequency. It's much easier to derive a low frequency output clock using a PWM timer and observe that on a buffered output pin.
     
  8. VoodooMojo

    Active Member

    Nov 28, 2009
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    I can play a lot of songs on my guitar with only one string on it but it sure is nice to have the other 5 there too.
    most beginners learn with 6 strings also, if you like banging around with one string, knock yourself out.
     
  9. retched

    AAC Fanatic!

    Dec 5, 2009
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    Ive got a one string bass guitar! But you are right, the other strings are helpful.

    The higher speed scopes take more accurate readings at lower "speeds"

    You want to look at samples per second when looking at digital scopes.

    Taken from TEKs XYZs of Oscilloscopes:
    Sample Rate – Refers to how frequently a digital oscilloscope takes a
    sample of the signal, specified in samples per second (S/s).

    Bandwidth – A frequency range, usually limited by –3 dB.

    A good read on O'scopes:
    www.tek.com/Measurement/App_Notes/XYZs/glossary.html
     
    Last edited: Jan 13, 2010
  10. knowitall

    New Member

    Jan 10, 2010
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    If you think your new hobby will become a lifes quest, then dedicate your computer to what it's intended for, data gathering , I.E. dasheets, P.C. layout programs, and personal communications ect.
    and another area used for construction, experiments, trouble shooting, with traditional electronic test equipment, parts bin storage, soldering station, and a throw away computer for writing your code to you pic. chips, and real time emulation.
    A 20 mc. scope would be a good investment, you can buy a brand new protek, for 300 bucks !, with an buffered output for your next piece of equip. a freq counter.
    There's a start (works for me ) Hope it helped.
     
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