low-end scope
in [Design]
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From: Joerg on 2 Mar 2010 11:51 Phil Allison wrote: > "Joerg" >> When you do noise debugging as much as I do you'd be glad analog scopes >> are still around. Not that it's always fun but someone has got to do the >> job. One client instantly bought a Tek 2465 after they saw me working on >> their stuff. They had spent weeks with a Tek DSO and not found the >> problem, and neither could I until I got a "real" scope out of the trunk. >> > > > ** Bought a Rigol DS1052E DSO late last year, when the direct from China > price had dropped to that of a mid range hand held Fluke multimeter - I > paid A$407 including delivery to my door. > > Does everything the maker says - but still has ALL the drawbacks inherent > in DSOs too. While it can certainly do things my analogue scope cannot it is > all but *useless* for general service work on audio equipment. > > The noisy trace, lack of instant real time display plus serious ambiguity > displaying signals that have a wide bandwidth means one cannot trust what > you see on the screen is REALLY what is coming out of the item under test. > One thing those DSO will rarely do is this: Hang the scope probe onto a node in the amp, touch this that and the other thing and see if there is a pulsating wee fattening of the trace in one little spot because of a crossover oscillation that the designer had missed. > One annoyance is that even in "AUTO" sweep mode, all signals are displayed > for 2 seconds after they have disappeared at the input. > The Instek here is a bit better than that, but still, it can't replace the analog scopes. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Jan Panteltje on 2 Mar 2010 12:04 On a sunny day (Tue, 02 Mar 2010 08:17:55 -0800) it happened John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in <n5eqo597obv5faqni99sjvn5k826fugvbr(a)4ax.com>: >It is in the sense that no audio signal has anything like the s/n to >justify a 24-bit ADC or DAC, even if a real 24-bit part existed. And >the idea of even 12 bit linearity is silly when you are using >microphones, power amps, loudspeakers, and signal trains that >deliberately add distortion. Yes, and the brain has ways of removing unwanted noises. Personally in my place the environment noise would make 8 bit audio sufficient in many cases. I have runs tons of stuff through companders. Only late at night I would need 16 bits... OTOH the ear (or our hearing) is very much logarithmic, so we hear distortions even in very low volume passages. >But if I have 1 PPM of hum or DC offset in my NMR coil drivers, or 100 >PPM pos/neg asymmetry, users *will* complain. 100 PPM is only a factor 10000, not even 14 bits. >And how does an analog scope work better than a digital scope when >testing a 24-bit DAC? To reformulate the question: How are you gonna look at such a signal with an 8 bit ADC as in your scope? By putting some analog gain up front? >John > >
From: Joel Koltner on 2 Mar 2010 12:16 "John Larkin" <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in message news:is9qo5tdsopq2i34seqc4h8qq6snfid6u9(a)4ax.com... > The digitals have pixels and adc quantization, but the difference re: > an analog scope is more psychological than real. I've noticed that scopes with 640x480 or higher resolution LCDs tend to look much "better" than the lower-cost ones that are only 320x240, as the pixels are much more obvious in such a case (assuming a 5" or so LCD, that is).
From: Nico Coesel on 2 Mar 2010 13:14 Jan Panteltje <pNaonStpealmtje(a)yahoo.com> wrote: >On a sunny day (Mon, 01 Mar 2010 17:46:33 -0800) it happened John Larkin ><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in ><r4roo5dd2mjre06t8glvpun5dc9hgu9p53(a)4ax.com>: > >>On Mon, 01 Mar 2010 16:49:54 -0800, Joerg <invalid(a)invalid.invalid> >>wrote: >> >>>Jan Panteltje wrote: >>>> On a sunny day (Mon, 01 Mar 2010 15:30:11 -0800) it happened John Larkin >>>> <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in >>>> <h5joo5tu7iv486nr7g4pp69r0vpco1cnuc(a)4ax.com>: >>>> >>>>> I've gotten used to small, light, color digital scopes >>>> >>>> Mine has color too: Green. >>> >>> >>>Mine even glows in the dark. Now that's something DSOs can't do :-) >> >>Yeah, but how long can you hold it out at arm's length? >> >>Now whenever I use an analog scope - which is seldom - I get confused >>about which trace is which. I don't miss black+white TV sets, or >>typewriters and carbon paper, or analog VOMs, or slide rules, or 300 >>baud acoustic modems either. >> >>John > >Wow, and that from somebody who swears by writing and drawing on deads trees :-) >And I do not miss the noise of that horrible Tek digital I once had to use for audio. Probably a TDS200 series. There are noisy as hell. -- Failure does not prove something is impossible, failure simply indicates you are not using the right tools... nico(a)nctdevpuntnl (punt=.) --------------------------------------------------------------
From: Joerg on 2 Mar 2010 13:50
miso(a)sushi.com wrote: > On Mar 1, 4:49 pm, Joerg <inva...(a)invalid.invalid> wrote: >> Jan Panteltje wrote: >>> On a sunny day (Mon, 01 Mar 2010 15:30:11 -0800) it happened John Larkin >>> <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote in >>> <h5joo5tu7iv486nr7g4pp69r0vpco1c...(a)4ax.com>: >>>> I've gotten used to small, light, color digital scopes >>> Mine has color too: Green. >> Mine even glows in the dark. Now that's something DSOs can't do :-) >> >> -- >> Regards, Joerg >> >> http://www.analogconsultants.com/ >> >> "gmail" domain blocked because of excessive spam. >> Use another domain or send PM. > > The old HP scope cameras had UV lights in the to illuminate the > graticle. The one that glows is a Tek 7704A mainframe. When I need to go back to the office at night to pick up a document and it's pitch dark there is this eerie blue glow from that CRT. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. |