Should I get an analog oscilloscope to supplement my digital one?

Discussion in 'General Electronics Chat' started by tom66, Aug 5, 2011.

  1. tom66

    Thread Starter Senior Member

    May 9, 2009
    I currently have a quad channel 100 MHz HP 54501A digitising oscilloscope, which I bought about 2 years ago. But I am finding its 10 M/S limit a pain, as well as other limitations from a nearly 18 year old digital oscilloscope.

    Recently I started looking at power supplies. You just can't get the same feel as an analog scope as there is really no true persistence mode, except on the higher-end DPO models, which cost a lot of money.

    Here, I wanted to see what the output ripple of a small buck power supply was. This image (scale 50mV/div) seems to suggest that the ripple extends as much as 100mVp-p; but it is only ~60mVp-p on average as not all parts of the waveform occur with the same "probability". My question is, would an analog scope be more suited to this than with the persistence mode of my digital scope? I can buy a low-end 20 MHz oscilloscope for around £40-50, and am wondering if it would suit my needs well.
    Last edited: Aug 5, 2011
  2. Hi-Z

    Active Member

    Jul 31, 2011
    Well, when I used to practise the gentle art of electronics (a few years ago now), I used to find most digital 'scopes were a pain in the **** to use - especially those made by a rather huge and famous corporation. (Don't get me wrong, they most certainly have their uses!)

    Whereas most analog 'scopes are a joy to use. And they have knobs, where the digital 'scope has stupid buttons. Don't hesitate, just do it, would be my advice.
  3. Adjuster

    Well-Known Member

    Dec 26, 2010
    At least at a "budget" price level, some aspects of performance are better with analogue. That said, new analogue instruments are getting progressively rarer, and possibly may not be supported by their manufacturers for much longer. Buying second-hand, you take more of a risk. Your £50 scope may turn out to have a tired tube which would render low-probability events invisible.

    The lack of a persistence function to visually indicate paint density is a real handicap, for instance when displaying something like a noisy eye pattern. Even the big players took a while to address this, initially only in very expensive wideband machines. The price level at which such functions are offered has been reducing over the years, but whether they will ever drop to level that you would consider remains to be seen.

    As for user-friendliness, knobs vs. buttons etc, some of the earlier digital scopes were very much worse in this respect than present offerings. You might be pleasantly surprised by an up-to-date machine. It is true though that the typically menu-driven operation makes more demands on the operator's memory. This may be easier for youngsters than for those of us from an older generation.

    In the end, it probably comes down mainly to how much you are prepared to spend, and how long you need it to last. You can't expect much for fifty quid!
  4. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    I think I have that same scope on my bench at work. It's a definate downgrade for me as I used to have a nice Tektronics TDS, which is set by nice twirly knobs and not a keyboard. Resolution of the TDS was also superior then the HP.

    Analog scopes do hold the edge on (of course) random analog signals, especially things like measuring peak to peak noise. Digital scopes shine when given single event triggers.

    As you can get very nice analog scopes on the used market for a song then it's kind of a no brainer to get an additional analog scope.
  5. Alchymist

    New Member

    Apr 16, 2011
    Cost a bit more than a song, and somewhat large, but I do like my Tek 7104. ;)
  6. #12


    Nov 30, 2010
    I've had phillips PM 3226 since 1976. Only repaired it once. Add one like that to your existing digital scope and you should have everything you need, I think.