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Recommendations for Oscilloscope.

Discussion in 'Electronic Basics' started by Daniel Pitts, Aug 10, 2012.

  1. Daniel Pitts

    Daniel Pitts Guest

    As I get more advanced at creating circuits, I can see the benefit to
    owning an Oscilloscope. I'm on a fairly tight budget, and was hoping to
    get a recommendation on a cheap oscilloscope that is "good enough" for
    hobby work. I've used one at school years ago, which probably had more
    bells and whistles than I would ever need.

    What features are essential for a hobbiest? What can I do without? Any
    particular brands that are cheap but reliable?

    Thanks for suggestions,
    Daniel.
     
  2. Winston

    Winston Guest

    For what it does, this is Dirt Cheap:

    http://www.ebay.com/itm/Tektronix-TDS350-1GS-S-200MHz-Scope-with-Printer-
    and-Com-Options-/150875129110?pt=BI_Oscilloscopes&hash=item2320dbc516

    No relation to the seller.

    The TDS scopes are a joy to use.

    --Winston
     
  3. I'm guessing that "what it does" (e.g., Ghz sampling) is way beyond
    Daniel's "good enough". And that $300 is quite a bit beyond his idea of
    "cheap". But who am I to put words on the OP's mouth.

    Maybe a 100Mhz, 2 ch older Tek, no more than $150.
     
  4. Winston

    Winston Guest

    On Fri, 10 Aug 2012 18:29:06 -0400, Bob Engelhardt wrote:


    (...)
    Yup. Without numbers, it's impossible to define 'cheap'.

    It is possible to pay too little for a scope, though.
    I paid $50 for a couple Tek scopes, a 531 and a 551.
    Getting them working was a hoot, but they were real
    'space heaters' and I seldom used them.

    So I bought a new Hitachi V-1100A for $1150. It's a good tool
    and has served me well.

    --Winston<-- That TDS 350 is still very lust-worthy, however.
     
  5. Phil Allison

    Phil Allison Guest

    "Daniel Pitts"

    ** This is cheap and ought to do you for a while.

    http://www.ebay.com.au/itm/Tektroni...05349?pt=BI_Oscilloscopes&hash=item2572efc205

    If you imagined buying NEW scope, then this is OK too.

    I have one just like it - very easy to use.

    http://www.electronickits.com/gold/CKOSCOPE10MHZ_Low_Cost_10MHZ_Oscilloscope.htm




    .... Phil
     
  6. Bob Masta

    Bob Masta Guest

    Depends on what you want to do. If you are working at audio
    frequencies you probably don't need a GHz-capable scope,
    like you would for high-speed digital stuff.

    I got by for years with an ancient 10 MHz Heathkit IO-103
    that I built from a kit. It was certainly good enough for
    the mostly-audio stuff that I was interested in at the time,
    and "high speed" digital was only in the low MHz range.

    Eventually I worked up to a 100 MHz B&K Precision 1580 (a
    "bargain" at $800 back then!) and it's done everything I
    needed since.

    Now, I'd go with other's recommendations for a decent used
    scope.

    <shameless plug> In addition to a "real" benchtop scope,
    you might want to take a look at my Daqarta software that
    uses your Windows sound card. The sound card limits it to
    "audio" range, but these days that can be nearly 100 kHz.
    HOWEVER, despite what some "premium" cards seem to imply,
    sound cards don't go down to DC... so you'll still need that
    benchtop scope.

    But despite the bandwidth limitations, there are some
    powerful features that you won't find elsewhere. The
    built-in 2-channel signal generator can create just about
    any signal you want, with 4 independent "streams" per
    channel. Each stream can be a simple or modulated waveform.
    The base waveforms are Sine, Triangle, Ramp (with
    controllable slopes that can also be modulated), Square,
    Pulse (monophasic or biphasic, controllable phase heights
    and widths), Arbitrary (from a file you supply), Play
    (complete recordings can be played at any speed, forward or
    backward, modulated, etc), uniform White noise, Gaussian
    noise, Pink noise, and Band-limited noise.

    The modulation options include Burst (with complete control
    over rise, fall, duration, lag, and cycle times, and
    rise/fall shape), AM, FM, PWM for pulse waves or phase
    modulation for others, or Sweeps (which can be linear or
    exponential, continuous or stepped). Modulation sources can
    be simple sine waves, or can use the output of other
    streams. Complete setups can be saved and instantly loaded.

    On the input side, besides standard waveform display Daqarta
    offers Spectrum and Spectrogram modes. Advanced signal
    averaging allows you to extract signals that are buried in
    noise, if they are synchronous with a clean "stimulus"
    signal. (Used for "evoked potentials" to measure hearing in
    animals and infants, for example).

    Trigger controls include the usual, plus Hysteresis to allow
    you to get a stable view of a noisy trace. Delay allows you
    to see events that happened up to 32Ksamples (over a half
    second) before or after the trigger. Holdoff allows you to
    sync to the start of a burst while ignoring events during
    the burst. There is also a Generator sync, so you can (for
    example) trigger on an FM modulating frequency.

    There is also a built-in frequency counter with high
    precision at low frequencies via reciprocal period methods.

    Built-in true RMS voltmeter and SPL meters are available if
    you calibrate your system.

    Daqarta includes a built-in macro language, and now includes
    a number of standard "mini-apps" that can be used as-is, or
    as the basis for your own applications. Some that you may
    be interested in are THD meter, IMD meter, Phase meter,
    Chart recorder, and (for fun, mostly) Lissajous figures.

    NOTE that after the 30-day/30-session free trial, the
    external inputs stop working, but the outputs are not
    affected... so the signal generator is yours to keep, for
    FREE. (Also file analysis, etc.) So even if you don't buy
    it (US$29, or $99 for the Pro version) you might want to
    install it on an old laptop and keep it on your bench next
    to your hardware scope, with my best wishes. Enjoy!

    Best regards,



    Bob Masta

    DAQARTA v7.00
    Data AcQuisition And Real-Time Analysis
    www.daqarta.com
    Scope, Spectrum, Spectrogram, Sound Level Meter
    Frequency Counter, Pitch Track, Pitch-to-MIDI
    FREE Signal Generator, DaqMusic generator
    Science with your sound card!
     
  7. Daniel Pitts

    Daniel Pitts Guest

    Yeah, I suppose I should have been more specific, although I really
    didn't have any idea of what the ranges of Oscilloscopes were.
    Something less than $250, I could buy pretty much right away. More than
    that I'd have to plan for and save up, which is also fine.

    As far as sampling rates, I'd be working with digital circuits running
    in the 10-30MHz range mostly, so more than audio, but I have no need for
    GHz.

    I didn't think about the fact that I could/should look for used, but
    actually for this type of equipment that makes sense to me.

    Thanks,
    Daniel.
     
  8. Tom Biasi

    Tom Biasi Guest

    The link Phil gave you is a good scope for the money, I used one for years.
    Note the shipping cost is to Australia, click in USA and it's about 40
    bucks.
    Here is Phil's link:
    http://www.ebay.com.au/itm/Tektroni...05349?pt=BI_Oscilloscopes&hash=item2572efc205
     
  9. Daniel Pitts

    Daniel Pitts Guest

    Cheap until you account for the "postage" of $180.
    Looks reasonable.

    When an oscilloscope says 10MHZ, what exactly does that mean? Is that
    the highest frequency it can reliable display?

    Thanks,
    Daniel.
     
  10. Fred Abse

    Fred Abse Guest

    No.

    It's the frequency at which the response has fallen to 0.707 of the
    response at DC. -3dB, or half power.
     
  11. Guest

    It means that the vertical amplifier has a bandwidth of 10MHz. That is, a 1V
    10MHz sine wave will appear as a .7V sine wave. A 1V 10MHz square wave will
    look about the same. ;-)

    If you're looking at digital circuits, the rule-of-thumb is that you want a
    bandwidth of at least 5x the fastest signal you're likely to see. If your
    logic is 20MHz, you want a bandwidth of at least 100HMz.
     
  12. Jon Kirwan

    Jon Kirwan Guest

    So let's say "mostly" also means sometimes more than 30MHz.
    Say 40MHz. So for a clean waveform you will want about 5x or
    200MHz, though at your level of interest it's possible 100MHz
    would be fine. For sampling, you'd need a minimum of twice
    that but really it should be more than twice. So the 1GHz
    sampling really isn't so shocking, as you can see. It "gets
    you by", is all.

    The Rigol 1102e is specified as a 100MHz scope and it samples
    at 1GHz (according to the specs, again.) So you need to keep
    things in some perspective. Roughly, the sample rate is about
    10x the bandwidth.

    By the way, the above mentioned Rigol DS1102e might be
    something to consider. Do a seach and see what you find.

    Oh, and check to make sure that whatever you buy comes with
    probes and a manual. More probes are better. You want to have
    1X and 10X probes, 2 each of the 10x at least, and maybe a
    100x even.

    If your budget were higher, or you get lucky, you might
    consider an MSO (mixed signal.) That gives you digital data
    probes along with the analog. What I have for this is an HP
    54645D -- 100MHz analog, plus 2+16 digital channels (32 with
    both probe cables set up.) This makes digital circuits a
    breeze to view.

    Jon
     
  13. tuinkabouter

    tuinkabouter Guest

    If you do only digital, than have a look at open bench logic sniffer.
    http://gadgetfactory.net/logicsniffer/
    16/32 channels max 200Mhz/100Mhz sampling rate.
    only $50
     
  14. Phil Allison

    Phil Allison Guest

    "Daniel Pitts"
    ** Well, you did not say where you live.

    Nothing in your details gives a clue it is Australia.

    ** For an ANALOGUE scope, it indicates the highest frequency where you can
    still measure the amplitude with some accuracy. But crucially, it also means
    the scope will display any frequency up, to that frequency, at any setting
    of the time base.

    IOW the scope will display the anything range from DC to 10 MHz both
    simultaneously and unambiguously.

    Digital scopes ( or DSOs) will not do this.


    ..... Phil
     
  15. Phil Allison

    Phil Allison Guest

    "Bob Masta"
    ** It is a fallacy to imagine that a scope used mostly for "audio" only
    needs to cover the audio band and a bit beyond.

    The error arises from associating the abbreviation "audio " with " audio
    frequency " instead of the intended meaning of ** audio equipment **.

    Audio equipment, even going back decades ago, includes:

    1. Amplifiers employing valves, transistors or mosfets.

    2. AM and FM radio receivers.

    3. Wireless microphones.

    4. Digital audio and digital musical instruments.

    An audio power amplifier that is working correctly will not involve
    frequencies much above 100kHz - BUT a faulty amplifier may exhibit
    oscillations at up to 50MHz, particularly mosfet examples. You need to be
    able to see it on the scope to fix it.

    FM broadcast receivers have an IF strip at 10.7 MHz that can need to be
    viewed.

    Wireless mic transmitters have crystal oscillators operating at 50MHz or
    more that need to be checked.

    An audio tech may be presented with CB radio or RC model control gear to fix
    too - I have.

    I use a good, dual trace 50MHz analogue scope for "audio" - and it is just
    good enough.

    I also own but do not use a 50MHz DSO, as I find it very unsatisfactory for
    servicing or troubleshooting work.


    .... Phil
     
  16. Bob Masta

    Bob Masta Guest


    Agreed 100%! I really was just "getting by" with that 10
    MHz unit... and sometimes I did encounter oscillating power
    amps. The clue was a "fat" trace, from the (greatly
    attenuated) HF crap riding on the signal. It was enough to
    know that there was a problem, without needing to see the
    exact frequency or waveform of the oscillation.

    Never got much into receivers and transmitters. When I
    started out there was no such thing as digital audio (at
    least, not outside of lab curiosities).

    Things are a bit different today!

    Best regards,


    Bob Masta

    DAQARTA v7.00
    Data AcQuisition And Real-Time Analysis
    www.daqarta.com
    Scope, Spectrum, Spectrogram, Sound Level Meter
    Frequency Counter, Pitch Track, Pitch-to-MIDI
    FREE Signal Generator, DaqMusic generator
    Science with your sound card!
     
  17. I paid five dollars for my first oscilliscope, ac coupled, no triggered
    sweep, but it got me a scope. If one can get one that cheap (or my 535?
    that someone found in the hospital garbage for me), one then proceeds to
    play with it, seeing what the knobs do and trying to learn as much as
    possible from it.

    Then when they spend "real money" they have a handle on what might be
    useful for their own purposes. They learn from the experience of the free
    or really cheap oscilliscope, which enables them to make a better decision
    when spending the money. Asking here doesn't really change things, they
    are depending on someone else to tell them "a good price" and 'what they
    need".

    They may find they can live without things. A really cheap scope is
    likely going to be limited (or old), but they may find that the
    limitations are within what they are doing right now, so it doesn't
    matter.

    Or they may discover they don't need a scope, so having spent that five
    dollars they have learned quite a bit.

    Michael

    Hitachi V-1100A for $1150. It's a good tool > and has served me well.
     
  18. Daniel Pitts

    Daniel Pitts Guest

    Indeed, I'm not in Australia. I wasn't paying too close attention to the
    words on that page, only the numbers. I am in the USA (California
    specifically).
    Okay, but if the frequency starts to get up to (say) 30MHz, I'll end up
    with aliasing? Or just a decrease in amplitude? Or both?

    If I don't care about the amplitude of the signal, only the shape, is a
    10MHz scope good enough for viewing higher frequencies?

    Thanks,
    Daniel.
     
  19. Fred Abse

    Fred Abse Guest

    If the shape is not a pure sine wave, inadequate bandwidth will distort
    it. Not just the amplitude.

    A 10MHz square wave, displayed on a 10MHz oscilloscope will look far from
    square.
     
  20. Winston

    Winston Guest

    On Mon, 13 Aug 2012 20:48:34 -0400, Michael Black wrote:


    (...)
    That's why I really like Freecycle.
    http://www.freecycle.org/

    I know that I can pass valuable gear on to less experienced folks
    for them to enjoy (and get very cool gear for *me* to enjoy!)

    --Winston
     
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