A good digital oscilloscope?
in [Design]
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From: Joerg on 8 Dec 2009 20:01 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 $30k analyzer didn't pick it up. [...] -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Joerg on 8 Dec 2009 20:02 Jan Panteltje wrote: > On a sunny day (Tue, 08 Dec 2009 11:01:40 -0800) it happened Joerg > <invalid(a)invalid.invalid> wrote in <7o7m4oF3obbsiU3(a)mid.individual.net>: > >> Jan Panteltje wrote: >>> On a sunny day (Mon, 07 Dec 2009 23:29:59 GMT) it happened Jan Panteltje >>> <pNaonStpealmtje(a)yahoo.com> wrote in <hfk360$i5i$1(a)news.albasani.net>: >>> >>>> Just be studying that diagram, there is an intensity preset pot, good, >>>> maybe that is all I need to tweak, (it is too bright, cannot dim it). >>>> Could accidently have turned that during calibration... >>> Yes that was it, VR108, scope is as new again :-) >> >> 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 http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: John Larkin on 8 Dec 2009 20:20 On Tue, 08 Dec 2009 16:55:47 -0800, Joerg <invalid(a)invalid.invalid> wrote: >John Larkin wrote: >> On Tue, 08 Dec 2009 19:09:03 GMT, Jan Panteltje >> <pNaonStpealmtje(a)yahoo.com> wrote: >> >>> On a sunny day (Tue, 08 Dec 2009 10:58:50 -0800) it happened Joerg >>> <invalid(a)invalid.invalid> wrote in <7o7lveF3obbsiU2(a)mid.individual.net>: >>> >>>>>>> ftp://panteltje.com/pub/DVD_remote_fluorescent_buttons_img_1676.jpg >>>>>> Try some strontium aluminate. It's something like 10x better a light >>>>>> storage thing than the old ZnS stuff. >>>>>> >>>>>> John >>>>> The DVD remote in the above link *is* strontium aluminate, >>>>> I just did the 4 minute test, >>>>> http://en.wikipedia.org/wiki/Phosphorescence (scroll down) >>>>> still clearly visible, not adapted eyes, also after 5 minutes. >>>>> The color also matches tha tbird... >>>>> They say the ZnS stuff is no longer used... >>>>> The real 'hot' stuff I remember from my youth was 'radium', >>>>> radium on watches, clocks, and even on some light switches. >>>>> That was all no longer allowed at some point. >>>> >>>> Back in those days watch dials would be readable all night, not nearly >>>> have that much decay. That is no longer the case, no matter what fancy >>>> material they use. >>> No problem, you can have it if you want: >>> Tritium: >>> http://en.wikilib.com/wiki/Tritium >>> Tritium watch: >>> http://en.wikipedia.org/wiki/File:Tritium-watch.jpg >>> Tritium alarm clock: >>> http://www.ultralux.ch/de_shop.cfm?cmd=detail&id=48&pid=142¤t=1&mainkat=5 >> >> I put tritium lights on the tops of the bedposts in the cabin... it's >> really dark up there, and you can whack yourself in the head coming >> back from peeing. I had to order them from England, as I think they >> are illegal in the USA. >> > >Doesn't seem to be illegal, I have a Chase-Durer watch similar to this one: > >http://www.amazon.com/Chase-Durer-Blackhawk-Mach-3/dp/B000X1X5EO > >Those are American watches, I didn't import it. But IMHO its tritium >illumination still ain't as good as the stuff from the olden days. Tritium watches and gunsights seem available in the US, but these keychain lights aren't. The ebay units are shipped from Hong Kong or the UK, possibly illegally. > > > >> ftp://jjlarkin.lmi.net/Tritium.jpg >> > >Nice. But one thrashing with the bed sheets and ... chop ... thwack. The top of the post is about head level, a bit high for sheet-whacking. We acquired this hideous bed when we got the cabin. I'd >probably have gone with a recessed LED blinkenlight that barely sticks >out above the post. I was going to do that, a Tadiran lithium battery, a meg or so, and a green LED, but I would have had to drill some big holes in the wood to drop all that hardware in. The lithium+led would stay lit for at least 20 years. ftp://jjlarkin.lmi.net/Tadiran.JPG I once did a test with a uC operating a strobe (like >you see on aircraft) and played with the timer values. It's amazing how >miniscule a duty cycle the human eye recognizes when it's dark. Even >when I put a PWM-ramp in so it doesn't irritate much. I posted some weeks back about experimenting with an Agilent green LED that was visible to my dark-adapted eye at 1 nA. John
From: Joerg on 8 Dec 2009 20:26 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. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Joerg on 8 Dec 2009 20:32
John Larkin wrote: > On Tue, 08 Dec 2009 16:55:47 -0800, Joerg <invalid(a)invalid.invalid> > wrote: > >> John Larkin wrote: [...] >> >>> ftp://jjlarkin.lmi.net/Tritium.jpg >>> >> Nice. But one thrashing with the bed sheets and ... chop ... thwack. > > The top of the post is about head level, a bit high for > sheet-whacking. We acquired this hideous bed when we got the cabin. > Archie Bunker would have said that it would take Gloria and the meathead about five minutes :-) > I'd >> probably have gone with a recessed LED blinkenlight that barely sticks >> out above the post. > > I was going to do that, a Tadiran lithium battery, a meg or so, and a > green LED, but I would have had to drill some big holes in the wood to > drop all that hardware in. The lithium+led would stay lit for at least > 20 years. > > ftp://jjlarkin.lmi.net/Tadiran.JPG > > I once did a test with a uC operating a strobe (like >> you see on aircraft) and played with the timer values. It's amazing how >> miniscule a duty cycle the human eye recognizes when it's dark. Even >> when I put a PWM-ramp in so it doesn't irritate much. > > I posted some weeks back about experimenting with an Agilent green LED > that was visible to my dark-adapted eye at 1 nA. > Yes, I remember. That would be my kind of solution. Is it still running on your desk or did it disappear under a stack of schematics by now? -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. |