12 and 16-bit oscilloscopes
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From: Winfield Hill on 18 Dec 2006 21:59 Tom Bruhns wrote... > > Well, it won't fit in your "under $1500" budget, but HP/Agilent > for many years has been making a 23-bit 20Ms/s card. It's not > necessarily useful to 23 bits, but even by today's standards, > the distortion and spur performance isn't too shabby, and was > certainly cutting-edge when it was introduced. What part number was that? -- Thanks, - Win
From: Tom Bruhns on 18 Dec 2006 23:21 Winfield Hill wrote: > Tom Bruhns wrote... > > > > Well, it won't fit in your "under $1500" budget, but HP/Agilent > > for many years has been making a 23-bit 20Ms/s card. It's not > > necessarily useful to 23 bits, but even by today's standards, > > the distortion and spur performance isn't too shabby, and was > > certainly cutting-edge when it was introduced. > > What part number was that? Hi Win, It's the E1437A; it's a VXI module, and includes traditional dynamic signal analyzer functions like zoom and decimation. Cheers, Tom
From: Mike Monett on 19 Dec 2006 02:26 "Joel Kolstad" <JKolstad71HatesSpam(a)yahoo.com> wrote: >> I run DOS in Flat Real Mode (FRM) and store the data in Extended >> Memory. > I'm impressed with what you're able to do, but you realize you've > at least decimated your market by working on a product that > requires *DOS*???!!! > ---Joel DOS is still used for critical embedded applications, such as process control, where Windows is simply too unreliable, and Linux may be overkill. DOS also gives the fastest possible performance, since you own the cpu and don't have to give up cpu cycles for multitasking. That's the reason I mentioned it - the response while sifting through a megabyte of data was practically instantaneous from the keyboard, but it would be a bit slower in Windows. However, that was on a 450MHz AMD K6 cpu. I would expect higher performance on a more modern 2GHz+ cpu for home lab applications. Since the code is in Borland Pascal, it would be very straightforward to transfer it to Free Pascal and run it in Windows, or even to Linux running on an X86 machine. The main point is sifting through a megabyte of data can be very fast if you have taken a bit of care to optimize the code. Regards, Mike Monett Antiviral, Antibacterial Silver Solution: http://silversol.freewebpage.org/index.htm SPICE Analysis of Crystal Oscillators: http://silversol.freewebpage.org/spice/xtal/clapp.htm Noise-Rejecting Wideband Sampler: http://www3.sympatico.ca/add.automation/sampler/intro.htm
From: mike742 on 19 Dec 2006 02:53 > It's the E1437A; it's a VXI module, and includes traditional dynamic > signal analyzer functions like zoom and decimation. These are nice A/Ds but a bit hard to use. I'm not sure how much the zoom/decimation is worth these days as a PC can do it in real time (if you can get the data into it). To use an E1437A you need the VXI bus cage and slot 0 controller and software. To run at high speed you need to use the E1437A the HP VXI Local bus (100 Mbyte/second ECL) output. I've got a Pentek Model 4404 HP Local Bus-to-FPDP Adapter and a PC with a FPDP PCI card all cobbled together. http://www.pentek.com/Products/Detail.cfm?Model=4404 It's not perfect but it can run in 16 bit A/D mode at 20 Msamples/second and the PC can put out the resulting 40 MB/second over Gigabit ethernet (to the cluster).
From: John Devereux on 19 Dec 2006 04:00
"Tom Bruhns" <k7itm(a)msn.com> writes: > Mike Monett wrote: >> John Devereux <jdREMOVE(a)THISdevereux.me.uk> wrote: >> >> > "Joel Kolstad" <JKolstad71HatesSpam(a)yahoo.com> writes: >> >> >> "John Devereux" <jdREMOVE(a)THISdevereux.me.uk> wrote in message >> >> news:87d56hkrd9.fsf(a)cordelia.devereux.me.uk. >> >> >>> I would love to make a "scope" based on something like the >> >>> AD7660. It's a 24 bit 2.5MHz sigma delta ADC PC does post >> >>> processing for "triggering", averaging, spectrum analysis <SNIP> >> >> The AD7660 looks quite interesting. The 120dB SNR up to 78KHz is >> impressive. It might be a good compliment to the inherent >> noise-rejection capability of the Binary Sampler. This might produce >> an inexpensive scope with unique capability and wide bandwidth. >> > > ... > > Hi Mike, Joel and all, > > OK, the AD7660 is a 16-bit successive approximation ADC that's pretty > decent. The AD7760 is the 24-bit delta-sigma part. Sorry for the confusion, I did mean the AD7760 (the 24 bit 2.5MHz delta sigma that my link pointed to). > I'm not quite seeing the 120dB SNR in the data sheet for the > AD7760--looks like 112dB to me. At 78kHz bandwidth, that's about > -160dBfs/Hz. That's good, certainly, though it's not all that > different from a 130Ms/s part that has a 78dB SNR: such a part has a > noise level at about -156dBfs/Hz. Interesting; your implication is that one can obtain equivalent performance at lower frequencies by signal averaging, yes? So just pick the device with the highest sampling rate and low dBfs/Hz? > If it's really for a scope, my main interest in more bits would be to > avoid input ranging, and that's not all that difficult at low > frequencies (1MHz these days is "practically DC"...). But if it's for > spectral analysis, that's a different story. Then distortion and noise > are important (more important than the number of bits, which is largely > a red herring). > > My personal interest would be in fewer bits and much faster sampling: > maybe a Virtex 5 connected to two or four 500Ms/s converters, into a > deep buffer memory. My motivation was based on experience with a TDS3054 scope. I love it, but one thing it does not do is improve resolution at the lower sample rates. For one-shot events, you are stuck with the same ~7 bit resolution at 10kHz that it uses at 500MHz. It would be nice to have something optimized for low frequency use. -- John Devereux |