A good digital oscilloscope?
in [Design]
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From: Fred Bartoli on 9 Dec 2009 04:56 Joerg a �crit : > qrk wrote: >> On Tue, 8 Dec 2009 06:11:02 -0800 (PST), George Herold >> <ggherold(a)gmail.com> wrote: >> >>> On Dec 7, 2:56 pm, qrk <SpamT...(a)spam.net> wrote: >>>> On Sun, 06 Dec 2009 20:29:24 -0800, John Larkin >>>> >>>> >>>> >>>> >>>> >>>> <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >>>>> On Sun, 6 Dec 2009 22:18:04 -0600, "Tim Williams" >>>>> <tmoran...(a)charter.net> wrote: >>>>>> I never was too impressed with digital scopes. None of them have >>>>>> nearly >>>>>> enough buttons, so you spend all your time wading through menus. >>>>>> The Rigol >>>>>> I've used (don't remember the number) has awful menus, they are >>>>>> not always >>>>>> quite what they say they are, and they take forever to go away. >>>>>> Some digital scopes have better refresh than others. The HP >>>>>> (Agilent??) >>>>>> 54622D's in all the labs at school here work fairly well, though >>>>>> at least >>>>>> two button presses are required to reach any given menu option. >>>>>> Refresh is >>>>>> okay, though still chunky on slower sweeps (>1ms/div). >>>>>> My impression of the cheapass Tek TDS's (the thin rectangular >>>>>> ones) is >>>>>> similar to the Rigol. >>>>>> I'm most familiar with my Tek 475, but it would be nice to have >>>>>> storage, >>>>>> single sweep* and averaging. One of those intermediate scopes, >>>>>> the ones >>>>>> with analog AND digital, they're perfect for everything. >>>>>> *Just because it's an analog scope doesn't mean you don't get >>>>>> storage or >>>>>> single sweep type readings, it just means it takes more setup. This >>>>>> photograph was taken with a 10 second exposure, capturing three >>>>>> photoflash >>>>>> discharges: >>>>>> http://webpages.charter.net/dawill/Images/Photoflash_Discharge2_sm.jpg >>>>>> >>>>>> Tim >>>>> I like my TDS2012. I rarely use an analog scope any more. >>>>> John >>>> I find that I use an analog scope (Tek 465) for analog stuff. Can't >>>> get a feeling for noise issues with a digital scope. For pulse >>>> amplifier stuff and when you need arithmetic, digital is the way to >>>> go. >>>> >>>> -- >>>> Mark- Hide quoted text - >>>> >>>> - Show quoted text - >>> Not sure what sort of noise you are looking at, but I love my digital >>> �scope for looking at noise. The trick I use is to trigger right up >>> at the top of the noise. Then I put the scope in average mode and you >>> get an image that looks like the auto correlation function. My >>> colleague has dubbed this the Quasi � auto- correlation function, >>> �Quacf� for short and of course pronounced quaff. (Ahh, nothing like >>> a good beer.) If you ask for the FFT of this �trace� you get a much >>> better picture. But I�ve become very good at reading quacf�s. >>> >>> George H. >>> >> >> I deal with high gain amplifiers (80 dB gain, around 256 channels per >> system) sitting in a sea of noise. Trying to pick out switching power >> supply noise, digital noise, AM & FM radio transmitters, and ground >> loop noise from other equipment is difficult with digital scopes since >> the structure of the noise is lost. I'll revert to frequency domain >> (usually a swept analyzer) to pick out the offending frequency if it's >> from a switcher, clock or radio station, but logic noise doesn't show >> up well in the frequency domain. ... > > > Ever tried a receiver? After a while you just listen to the rat-tat-tat > and chase it with a near field probe, without even looking at any > display. Occasionally when I do this with headphones on at a client the > guys look at me as if I was doing voodoo or some sort of exorcism. Until > the source is found and they are puzzled why their $30k analyzer didn't > pick it up. > > [...] > Hmmm, better not having tinnitus :-))) -- Thanks, Fred.
From: oopere on 9 Dec 2009 06:21 Nico Coesel wrote: > info_at_cabling-design_dot_com(a)foo.com (DA) wrote: > >> Hi all, >> >> I think I'm going to try and treat myself to an oscilloscope this >> Christmas. I've managed to go without one for the last 15 years or so and, >> frankly, did not have a burning need or even much space for it. I do some >> digital design (PIC based mostly) - LED, motor controls and such and >> every once in a while I wish I has something to look at the signal with. >> >> Are there people here using this brand? Are they any good for use in >> digital designs and, most importantly for me at this point, easy to learn? >> >> I guess, Rigol may not be the only ones making digital oscilloscopes these >> days. What other brands/models should I also look at? > > Also look at Owon (low end Tektronix) > You may also have a look at the 4 channel GW-Instek scopes. Till now, they have been working ok. Nice look and feel also. Pere
From: Jan Panteltje on 9 Dec 2009 07:01 On a sunny day (Tue, 08 Dec 2009 17:02:32 -0800) it happened Joerg <invalid(a)invalid.invalid> wrote in <7o8b9cF3oveo8U2(a)mid.individual.net>: >>> A friend of mine used to take off the aluminum front panels of similar >>> equipment and, <gasp>, put it in the dishwasher. He's divorced so I >>> guess no issues from that department :-) >>> >>> Afterwards it really looked like new. I was surprised that he never had >>> a case where the lettering came off, that's what I'd be conerned about. >> >> I use alcohol, 'spiritus' in Dutch. > > >Out here we use that for much more fun stuff :-)) > >-- >Regards, Joerg 'Spiritus' is 85% Ethanol, and 3% Methanol, plus a horribe smell and taste added... Vodka is expensive, and only 40%, heavely taxed here.
From: Jan Panteltje on 9 Dec 2009 07:22 On a sunny day (Tue, 08 Dec 2009 18:54:33 -0800) it happened Joerg <invalid(a)invalid.invalid> wrote in <7o8hrhF3o7d4jU1(a)mid.individual.net>: >> It might be this one... >> >> http://www.google.com/patents/about?id=0Nl6AAAAEBAJ&dq=7113750 >> > >Oh man, some of the patent examiners must really wave stuff through or >not pay much attention. Don't they use engineers anymore at the patent >office? This is a really old scheme, tons of prior art. Used on ECG >units dating almost back to the Romans. So I guess that patent wouldn't >have much standing if it ever came to a court challenge. > >But that's essentially how it's done right. Typically there is a >synchronous detector at the other side but the modulation scheme doesn't >really matter. On low frequency gear the carrier transformer supplies >power to the isolated side at the same time. Of course if the carrier >has to be in the GHz range you'd be better off with a third transformer. > >-- >Regards, Joerg Exactly!!!!
From: Joerg on 9 Dec 2009 10:36
John Larkin wrote: > On Tue, 08 Dec 2009 18:54:33 -0800, Joerg <invalid(a)invalid.invalid> > wrote: > >> John Larkin wrote: >>> On Tue, 08 Dec 2009 17:26:48 -0800, Joerg <invalid(a)invalid.invalid> >>> wrote: >>> >>>> John Larkin wrote: >>>>> On Tue, 8 Dec 2009 12:32:52 -0600, "Tim Williams" >>>>> <tmoranwms(a)charter.net> wrote: >>>>> >>>>>> "John Larkin" <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in message >>>>>> news:oh6th5903d58sogu3cj8vk3er6r6li9m32(a)4ax.com... >>>>>>> I love our TPS2024. 200 MHz, and all four channels and the trigger >>>>>>> input are fully floating. Wanna clip the probe ground lead onto the >>>>>>> source of a fet that's flailing 400 volts off ground? No problem. >>>>>> Tasty. >>>>>> >>>>>> What's C-to-ground like, is it basically a differential input (2 x 1M || >>>>>> 20pF) with a BNC input? >>>>>> >>>>>> Tim >>>>> Something like 35 pF from the BNC outer to ground. I'd prefer less. >>>>> But it's truly floating with pretty much infinite CMRR. I think it's a >>>>> microwave-range FM signal link or something. >>>>> >>>> Or maybe not. Tektronix went to great lengths WRT isolated channels. >>>> Here is a photo for an older scope from Olaf in the German NG: >>>> >>>> http://www.criseis.ruhr.de/tek222.jpg >>>> >>>> Every data bit seems to have its own personal transformer with trace >>>> "windings". That is some real engineering there. >>>> >>>> Whenever I had to do that (isolated signal transfer in medical) I took >>>> the analog signal and heaved it across just one transformer while >>>> another bigger one supplies the isolated side with power. Results in >>>> very small capacitance which is always a concern for stuff that goes >>>> inside a beating heart. >>> >>> It might be this one... >>> >>> http://www.google.com/patents/about?id=0Nl6AAAAEBAJ&dq=7113750 >>> >> Oh man, some of the patent examiners must really wave stuff through or >> not pay much attention. Don't they use engineers anymore at the patent >> office? This is a really old scheme, tons of prior art. Used on ECG >> units dating almost back to the Romans. So I guess that patent wouldn't >> have much standing if it ever came to a court challenge. > > Unless it's "as applied to oscilloscopes" or something. I recall > isolated-input opamps that did this many decades ago. > Yeah, I know a sad case where a company is being sued because the "new" patent applied to equipment with a blue front panel and they have a blue front panel, to express it a bit exaggerated. That sort of "system" is plain sick, it stifles innovation which will then move to countries with less onerous patenting. Like in Asia. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. |