12 and 16-bit oscilloscopes
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From: joseph2k on 17 Dec 2006 14:46 Chris Carlen wrote: > Bob wrote: >> Chris Carlen wrote: >> >>>Hi: >>> >>>Picotech seems to be the only supplier of these in low cost <$1500 >>>flavors. >>> >>>But they are discontinuing their 16-bit version which had 96dB dynamic >>>range: >>> >>>http://www.picotech.com/applications/resolution.html >>> >>>And there USB based 12-bit versions have 72dB rather than the 80dB of >>>the parallel port versions. I expect they will dump the parallel ports >>>eventually. >>> >>>This is a shame. The 16-bit unit is killer for low frequency/audio >>>amplifier testing and general spectrum analysis. The FFT functions on >>>8-bit fast DSOs from Tek and Agilent are of limited usefulness due to >>>meager 70dB range (with averaging). >> >> I wonder if picotech ever fixed the glaring bugs in their software? > [edit discouraging story] > > > Bummer. Now I'm disinclined to buy one. > > Any other experiences out there? > > > How about a different approach? semi-pro and pro audio offers some interesting prospects, such as 10 channels at 24 bits and 192 ksamples /s. requires firewire/1394 or usb2. start with RME/hammerfall please. -- JosephKK Gegen dummheit kampfen die Gotter Selbst, vergebens. --Schiller
From: Tom Bruhns on 17 Dec 2006 23:25 On Dec 17, 11:46 am, joseph2k <quiettechb...(a)yahoo.com> wrote: > Chris Carlen wrote: > > Bob wrote: > >> Chris Carlen wrote: > > >>>Hi: > > >>>Picotech seems to be the only supplier of these in low cost <$1500 > >>>flavors. > > >>>But they are discontinuing their 16-bit version which had 96dB dynamic > >>>range: > > >>>http://www.picotech.com/applications/resolution.html > > >>>And there USB based 12-bit versions have 72dB rather than the 80dB of > >>>the parallel port versions. I expect they will dump the parallel ports > >>>eventually. > > >>>This is a shame. The 16-bit unit is killer for low frequency/audio > >>>amplifier testing and general spectrum analysis. The FFT functions on > >>>8-bit fast DSOs from Tek and Agilent are of limited usefulness due to > >>>meager 70dB range (with averaging). > > >> I wonder if picotech ever fixed the glaring bugs in their software? > > [edit discouraging story] > > > Bummer. Now I'm disinclined to buy one. > > > Any other experiences out there?How about a different approach? semi-pro and pro audio offers some > interesting prospects, such as 10 channels at 24 bits and 192 ksamples /s. > requires firewire/1394 or usb2. start with RME/hammerfall please. One thing to be a little careful about with cards that are designed to digitize audio is that they may use ADCs which indeed output 192k samples per second, but which have internal digital filters which will NOT allow response beyond 1/4 the output sample rate, or thereabouts. If the design of the board has limits in the analog signal path, you may be able to bypass that, but it will be difficult to deal with an ADC like that. In doing a survey of ADCs for such an application, I found more than one that was unacceptable for that reason. I believe a few also have highpass filters that would prevent them from going to DC, and in any event you might have to hack the software to disable such a filter. If you want a highpass, it's nice to do it digitally, because you can insure zero offset voltage, and many high-end audio ADCs have at least the ability to do it in their digital processing. (Practically all audio ADCs these days are delta-sigma type, with a lot of digital filtering and decimation going on inside.) Cheers, Tom
From: Mike Monett on 18 Dec 2006 02:54 "Tom Bruhns" <k7itm(a)msn.com> wrote: [...snip good info] > (Practically all audio ADCs these days are delta-sigma type, with a lot > of digital filtering and decimation going on inside.) > Cheers, > Tom Can you tell us which boards had response to DC? Which ones would you recommend for an inexpensive low-end pc scope? Regards, Mike Monett
From: Tom Bruhns on 18 Dec 2006 11:53 Mike Monett wrote: > "Tom Bruhns" <k7itm(a)msn.com> wrote: > > [...snip good info] > > > (Practically all audio ADCs these days are delta-sigma type, with a lot > > of digital filtering and decimation going on inside.) > > > Cheers, > > Tom > > Can you tell us which boards had response to DC? > > Which ones would you recommend for an inexpensive low-end pc scope? Hi Mike, Sorry if I wasn't clear about that. I was doing a survey (and not a terribly complete one at that) of high resolution ADC parts that would be useful in a digitizer that went to at least 80kHz bandwidth. I can't tell you about any of the boards; I don't have info on what ADCs they actually used. There may be good reasons to sample audio faster than 44.1ks/s, but extending the digitized bandwidth much beyond 20kHz is probably not very high on the list. Cheers, Tom
From: John Devereux on 18 Dec 2006 13:09
"Tom Bruhns" <k7itm(a)msn.com> writes: > Mike Monett wrote: >> "Tom Bruhns" <k7itm(a)msn.com> wrote: >> >> [...snip good info] >> >> > (Practically all audio ADCs these days are delta-sigma type, with a lot >> > of digital filtering and decimation going on inside.) >> >> > Cheers, >> > Tom >> >> Can you tell us which boards had response to DC? >> >> Which ones would you recommend for an inexpensive low-end pc scope? > > Hi Mike, > > Sorry if I wasn't clear about that. I was doing a survey (and not a > terribly complete one at that) of high resolution ADC parts that would > be useful in a digitizer that went to at least 80kHz bandwidth. I > can't tell you about any of the boards; I don't have info on what ADCs > they actually used. There may be good reasons to sample audio faster > than 44.1ks/s, but extending the digitized bandwidth much beyond 20kHz > is probably not very high on the list. I would love to make a "scope" based on something like the AD7660. It's a 24 bit 2.5MHz sigma delta ADC <http://www.analog.com/en/prod/0,,AD7760,00.html>. I was thinking - USB powered - buffer data in local SDRAM - Hi-speed USB interface - local SDRAM chip to buffer samples - *all* samples streamed to controller PC - PC does post processing for "triggering", averaging, spectrum analysis -- John Devereux |