Forums

DIY PC Oscilloscope

Started by Unknown March 9, 2013
"Francesco Poderico" <francescopoderico@googlemail.com> wrote in message 
news:7761a6e9-3011-472a-bc86-63c749a482a8@googlegroups.com...
> Actually in theory I could use the DLL inside the FPGA and changing the > clock phase with a resolution of 25 ps... so in theory I have a 1 GSPS > FPGA for repetitive signals!
Nah, 25ps resolution means you can take acquisitions shifted in time every 25ps -- 40GSPS equivalent! But, do beware of the manufacture and temperature variation of the delay. FPGAs are made for worst-case timing constraints, and anything that's adjustable (like a DLL) is put inside a loop (hence, DL*L*).
> Do you think it would make more attractive to buy?
Heck, make it better than a Rigol, from cheaper parts. And open source it (if it's that kind of project). Create shock waves in the marketplace! ;-)
> Actually the maximum bandwidth is 70 MHz, I'm low filtering for > aliasing.
My TDS460 says "50GS/s ET" (Equivalent Time) on 1ns/div. Looks like it's actually filling the whole screen with that resolution, not just interpolating between samples. The 100MHz, ~10MS/s HP54600B goes down to 1 or 2ns/div or something like that, but it uses sinc interpolation on such fine scales. I don't know what a Rigol does for high sampling rates. If you skip antialiasing filters, you get sharper displays and equivalent time sampling. If you filter, you're basically saying: "Yep, I purchased this 200MS/s ADC, and the FPGA to run it, and I'm taking both of them over to the grinder and shaving off... ohh about 80% of the silicon, because... I like the smell?" Filtering basically negates the trigger generator, too. You could sample continuously and do the trigger digitally instead. Which... ...I think for any particular period between trigger crossings, you'd want to use some sort of interpolation to adjust the timing -- sample N is a bit below the threshold, and sample N+1 crossed the threshold by so-and-so and caused a trigger, so we know the dV/dt and can estimate where it *did* actually cross. So we can stack this sample period on top of the other, which crossed at whatever rate, by aligning it. Shift everything sideways by the calculated time difference, using a suitable interpolation (a simple quadratic spline would be reasonable, but a sinc interpolation might be more physically significant), then stack it up for display. The "stacking" itself could be an array of buffers (so you have a memory of many traces, and can perform statistics on them to generate the display -- decimate (view only one), average (which would now be a FIR "sliding average", which AFAIK, no scope manufacturer ever does for averaging mode!), peak detect, median, RMS + std dev., etc. This display process could, of course, be done for either acquisition method (continuous or triggered). But again, such hackery, though interesting, doesn't get your bandwidth back, it's just software diddling for not being clever enough to get the bandwidth and trigger right in the first place. :) Tim -- Deep Friar: a very philosophical monk. Website: http://seventransistorlabs.com
On Mar 9, 11:15=A0pm, Francesco Poderico
<francescopoder...@googlemail.com> wrote:
> On Saturday, 9 March 2013 21:30:36 UTC, Jeff Liebermann =A0wrote: > > On Sat, 9 Mar 2013 10:22:38 -0800 (PST), > > > francescopoder...@googlemail.com wrote: > > > >I've started designing a 200 MSPS Oscilloscope with a 25 MHz analog ba=
ndwidth, 3Ksample/channel buffer.
> > > >The oscilloscope can be connected to a PC via USB, and eventually via =
Ethernet and WiFi.
> > > >The =A0trigger is ( at moment) rising, falling... auto, normal. > > > >I would appreciate suggestions and or =A0comment for possible improvem=
ent and functionality that could make this oscilloscope interesting.
> > > >Francesco > > > There are plenty of similar USB scopes on the market with similar > > > specs. =A0Use their feature list as a checklist to see if you're missin=
g
> > > something. =A0I presume that you're asking for advice on how to make th=
e
> > > hardware unique in order to obtain a marketing advantage. =A0Most of th=
e
> > > product differentiation is in the software, so I'll comment only on > > > the hardware. =A0What *I* might want in a USB scope is (whether I'm > > > willing to pay for these is another question): > > > 1. =A0USB microscope camera on the probe tip so that I can see where I'=
m
> > > sticking the probe. > > > 2. =A0IR thermometer with LED targeting on the probe so that I can > > > simultaneously measure and record any localized heating. > > > 3. =A0Replacable front end so that when I inevitably blow it out, it ca=
n
> > > be easily replaced. > > > 4. =A0Built in function generator, pattern generator, arbitrary wavefor=
m
> > > generator, two tone generator, DDS generator, white/pink noise, sweep > > > generator generator. =A0Extra points for adding AM/FM/PM/pulse > > > modulation. > > > 5. =A0DC power output for powering active probes and assorted sensors. > > > 6. =A0Presumably, it's dual channel. =A0If so, make it stackable via a > > > common bus or preferably via ethernet, so that multiple units can be > > > conglomerated into a 4,6,8, etc channel scope. > > > 7. =A0Switchable low pass filter on input for high RF level > > > environments. > > > 8. =A0Self test and calibration check. > > > 9. =A0An accurate and readable schematic so I can fix it. > > > 10. Security cable to keep it from getting um.... borrowed. > > > 11. Built in smoke detector. > > > -- > > > Jeff Liebermann =A0 =A0 je...@cruzio.com > > > 150 Felker St #D =A0 =A0http://www.LearnByDestroying.com > > > Santa Cruz CA 95060http://802.11junk.com > > > Skype: JeffLiebermann =A0 =A0 AE6KS =A0 =A0831-336-2558 > > Thnanks Jeff, > I like the idea of the Cable that stop "unwanted borrowed" I will actuall=
y do this... not sure about the camera on probe :-)...
> > I may add a block diagram ( notthe full schematic) to show people how to =
calibrate the scope and some test points and hits to help people to self re= pair the scope.
> > also the function generator, could be a good sales point > > Thanks
the first thing I would add is USB isolation (data and power) so that when using usb and/or powering it from usb the scope is isolated from the pc -Lasse
<francescopoderico@googlemail.com> wrote in message 
news:c1ad2481-696a-4257-8242-a8c92169124b@googlegroups.com...
> Hi all, > I've started designing a 200 MSPS Oscilloscope with a 25 MHz analog > bandwidth, 3Ksample/channel buffer. > The oscilloscope can be connected to a PC via USB, and eventually via > Ethernet and WiFi. > The trigger is ( at moment) rising, falling... auto, normal. > > I would appreciate suggestions and or comment for possible improvement > and functionality that could make this oscilloscope interesting. > > Thanks, > Francesco
Been there done that. Spent many weeks putting together a box that I was very proud of, then purchased a Rigol that does everything it does plus a lot more and a lot better. Is this really a good use of your time and energy?
On Saturday, 9 March 2013 22:58:46 UTC, Lasse Langwadt Christensen  wrote:
> On Mar 9, 11:15=A0pm, Francesco Poderico >=20 > <francescopoder...@googlemail.com> wrote: >=20 > > On Saturday, 9 March 2013 21:30:36 UTC, Jeff Liebermann =A0wrote: >=20 > > > On Sat, 9 Mar 2013 10:22:38 -0800 (PST), >=20 > > >=20 > > > francescopoder...@googlemail.com wrote: >=20 > > >=20 > > > >I've started designing a 200 MSPS Oscilloscope with a 25 MHz analog =
bandwidth, 3Ksample/channel buffer.
>=20 > > >=20 > > > >The oscilloscope can be connected to a PC via USB, and eventually vi=
a Ethernet and WiFi.
>=20 > > >=20 > > > >The =A0trigger is ( at moment) rising, falling... auto, normal. >=20 > > >=20 > > > >I would appreciate suggestions and or =A0comment for possible improv=
ement and functionality that could make this oscilloscope interesting.
>=20 > > >=20 > > > >Francesco >=20 > > >=20 > > > There are plenty of similar USB scopes on the market with similar >=20 > > >=20 > > > specs. =A0Use their feature list as a checklist to see if you're miss=
ing
>=20 > > >=20 > > > something. =A0I presume that you're asking for advice on how to make =
the
>=20 > > >=20 > > > hardware unique in order to obtain a marketing advantage. =A0Most of =
the
>=20 > > >=20 > > > product differentiation is in the software, so I'll comment only on >=20 > > >=20 > > > the hardware. =A0What *I* might want in a USB scope is (whether I'm >=20 > > >=20 > > > willing to pay for these is another question): >=20 > > >=20 > > > 1. =A0USB microscope camera on the probe tip so that I can see where =
I'm
>=20 > > >=20 > > > sticking the probe. >=20 > > >=20 > > > 2. =A0IR thermometer with LED targeting on the probe so that I can >=20 > > >=20 > > > simultaneously measure and record any localized heating. >=20 > > >=20 > > > 3. =A0Replacable front end so that when I inevitably blow it out, it =
can
>=20 > > >=20 > > > be easily replaced. >=20 > > >=20 > > > 4. =A0Built in function generator, pattern generator, arbitrary wavef=
orm
>=20 > > >=20 > > > generator, two tone generator, DDS generator, white/pink noise, sweep >=20 > > >=20 > > > generator generator. =A0Extra points for adding AM/FM/PM/pulse >=20 > > >=20 > > > modulation. >=20 > > >=20 > > > 5. =A0DC power output for powering active probes and assorted sensors=
.
>=20 > > >=20 > > > 6. =A0Presumably, it's dual channel. =A0If so, make it stackable via =
a
>=20 > > >=20 > > > common bus or preferably via ethernet, so that multiple units can be >=20 > > >=20 > > > conglomerated into a 4,6,8, etc channel scope. >=20 > > >=20 > > > 7. =A0Switchable low pass filter on input for high RF level >=20 > > >=20 > > > environments. >=20 > > >=20 > > > 8. =A0Self test and calibration check. >=20 > > >=20 > > > 9. =A0An accurate and readable schematic so I can fix it. >=20 > > >=20 > > > 10. Security cable to keep it from getting um.... borrowed. >=20 > > >=20 > > > 11. Built in smoke detector. >=20 > > >=20 > > > -- >=20 > > >=20 > > > Jeff Liebermann =A0 =A0 je...@cruzio.com >=20 > > >=20 > > > 150 Felker St #D =A0 =A0http://www.LearnByDestroying.com >=20 > > >=20 > > > Santa Cruz CA 95060http://802.11junk.com >=20 > > >=20 > > > Skype: JeffLiebermann =A0 =A0 AE6KS =A0 =A0831-336-2558 >=20 > > >=20 > > Thnanks Jeff, >=20 > > I like the idea of the Cable that stop "unwanted borrowed" I will actua=
lly do this... not sure about the camera on probe :-)...
>=20 > > >=20 > > I may add a block diagram ( notthe full schematic) to show people how t=
o calibrate the scope and some test points and hits to help people to self = repair the scope.
>=20 > > >=20 > > also the function generator, could be a good sales point >=20 > > >=20 > > Thanks >=20 >=20 >=20 > the first thing I would add is USB isolation (data and power) so that >=20 > when using usb and/or >=20 > powering it from usb the scope is isolated from the pc >=20 >=20 >=20 > -Lasse
Good point, I was thinking to use an ADuM5xxxx from AD.
On Sunday, 10 March 2013 00:16:57 UTC, Bruce Varley  wrote:
> <francescopoderico@googlemail.com> wrote in message > > news:c1ad2481-696a-4257-8242-a8c92169124b@googlegroups.com... > > > Hi all, > > > I've started designing a 200 MSPS Oscilloscope with a 25 MHz analog > > > bandwidth, 3Ksample/channel buffer. > > > The oscilloscope can be connected to a PC via USB, and eventually via > > > Ethernet and WiFi. > > > The trigger is ( at moment) rising, falling... auto, normal. > > > > > > I would appreciate suggestions and or comment for possible improvement > > > and functionality that could make this oscilloscope interesting. > > > > > > Thanks, > > > Francesco > > > > Been there done that. Spent many weeks putting together a box that I was > > very proud of, then purchased a Rigol that does everything it does plus a > > lot more and a lot better. Is this really a good use of your time and > > energy?
I get the point... and your are not the first one to tell me that. but I believe that an oscilloscope is still an instruments a lot of electronic enthusiastic would love to have it if priced correctly. Marketing will be the biggest challenge in a market so competitive.
Francesco Poderico <francescopoderico@googlemail.com> wrote:

>On Sunday, 10 March 2013 00:16:57 UTC, Bruce Varley wrote: >> <francescopoderico@googlemail.com> wrote in message >> >> news:c1ad2481-696a-4257-8242-a8c92169124b@googlegroups.com... >> >> > Hi all, >> >> > I've started designing a 200 MSPS Oscilloscope with a 25 MHz analog >> >> > bandwidth, 3Ksample/channel buffer. >> >> > The oscilloscope can be connected to a PC via USB, and eventually via >> >> > Ethernet and WiFi. >> >> > The trigger is ( at moment) rising, falling... auto, normal. >> >> > >> >> > I would appreciate suggestions and or comment for possible improvement >> >> > and functionality that could make this oscilloscope interesting. >> >> > >> >> > Thanks, >> >> > Francesco >> >> >> >> Been there done that. Spent many weeks putting together a box that I was >> >> very proud of, then purchased a Rigol that does everything it does plus a >> >> lot more and a lot better. Is this really a good use of your time and >> >> energy? > >I get the point... and your are not the first one to tell me that. >but I believe that an oscilloscope is still an instruments a lot of electronic enthusiastic would love to have it if priced correctly. >Marketing will be the biggest challenge in a market so competitive.
Did you look what a Siglent scope costs on Ebay? IIRC its about US $180 including shipping from China. How do you expect to beat that? BTW Lecroy sells the exact same scope for a lot more. -- Failure does not prove something is impossible, failure simply indicates you are not using the right tools... nico@nctdevpuntnl (punt=.) --------------------------------------------------------------
Nico Coesel wrote:

> Francesco Poderico <francescopoderico@googlemail.com> wrote: > > >>On Sunday, 10 March 2013 00:16:57 UTC, Bruce Varley wrote: >> >>><francescopoderico@googlemail.com> wrote in message >>> >>>news:c1ad2481-696a-4257-8242-a8c92169124b@googlegroups.com... >>> >>> >>>>Hi all, >>> >>>>I've started designing a 200 MSPS Oscilloscope with a 25 MHz analog >>> >>>>bandwidth, 3Ksample/channel buffer. >>> >>>>The oscilloscope can be connected to a PC via USB, and eventually via >>> >>>>Ethernet and WiFi. >>> >>>>The trigger is ( at moment) rising, falling... auto, normal. >>> >>>>I would appreciate suggestions and or comment for possible improvement >>> >>>>and functionality that could make this oscilloscope interesting. >>> >>>>Thanks, >>> >>>>Francesco >>> >>> >>> >>>Been there done that. Spent many weeks putting together a box that I was >>> >>>very proud of, then purchased a Rigol that does everything it does plus a >>> >>>lot more and a lot better. Is this really a good use of your time and >>> >>>energy? >> >>I get the point... and your are not the first one to tell me that. >>but I believe that an oscilloscope is still an instruments a lot of electronic enthusiastic would love to have it if priced correctly. >>Marketing will be the biggest challenge in a market so competitive. > > > Did you look what a Siglent scope costs on Ebay? IIRC its about US > $180 including shipping from China. How do you expect to beat that? > BTW Lecroy sells the exact same scope for a lot more. >
Yeah, but it has Lecroy's name on it and that's like GOLD!!!!!!!!!!! :) Jamie
nico@puntnl.niks (Nico Coesel) writes:

> Francesco Poderico <francescopoderico@googlemail.com> wrote: > >>On Sunday, 10 March 2013 00:16:57 UTC, Bruce Varley wrote: >>> <francescopoderico@googlemail.com> wrote in message >>> >>> news:c1ad2481-696a-4257-8242-a8c92169124b@googlegroups.com... >>> >>> > Hi all, >>> >>> > I've started designing a 200 MSPS Oscilloscope with a 25 MHz analog >>> >>> > bandwidth, 3Ksample/channel buffer. >>> >>> > The oscilloscope can be connected to a PC via USB, and eventually via >>> >>> > Ethernet and WiFi. >>> >>> > The trigger is ( at moment) rising, falling... auto, normal. >>> >>> > >>> >>> > I would appreciate suggestions and or comment for possible improvement >>> >>> > and functionality that could make this oscilloscope interesting. >>> >>> > >>> >>> > Thanks, >>> >>> > Francesco >>> >>> >>> >>> Been there done that. Spent many weeks putting together a box that I was >>> >>> very proud of, then purchased a Rigol that does everything it does plus a >>> >>> lot more and a lot better. Is this really a good use of your time and >>> >>> energy? >> >>I get the point... and your are not the first one to tell me that. >>but I believe that an oscilloscope is still an instruments a lot of electronic enthusiastic would love to have it if priced correctly. >>Marketing will be the biggest challenge in a market so competitive. > > Did you look what a Siglent scope costs on Ebay? IIRC its about US > $180 including shipping from China. How do you expect to beat that? > BTW Lecroy sells the exact same scope for a lot more.
I've wanted to make something like a "dynamic signal analyser" that goes up to 1 or 10 MHz, instead of 100kHz like they all seem to. High dynamic range (16+ bit) low noise, with arb generator. I've got one of these, and I like it, but it is a big old slow beast of a thing: <http://www.teknetelectronics.com/Search.asp?p_ID=13689&pDo=DETAIL> -- John Devereux
On Sunday, 10 March 2013 16:35:29 UTC, Nico Coesel  wrote:
> Francesco Poderico wrote: > > > > >On Sunday, 10 March 2013 00:16:57 UTC, Bruce Varley wrote: > > >> wrote in message > > >> > > >> news:c1ad2481-696a-4257-8242-a8c92169124b@googlegroups.com... > > >> > > >> > Hi all, > > >> > > >> > I've started designing a 200 MSPS Oscilloscope with a 25 MHz analog > > >> > > >> > bandwidth, 3Ksample/channel buffer. > > >> > > >> > The oscilloscope can be connected to a PC via USB, and eventually via > > >> > > >> > Ethernet and WiFi. > > >> > > >> > The trigger is ( at moment) rising, falling... auto, normal. > > >> > > >> > > > >> > > >> > I would appreciate suggestions and or comment for possible improvement > > >> > > >> > and functionality that could make this oscilloscope interesting. > > >> > > >> > > > >> > > >> > Thanks, > > >> > > >> > Francesco > > >> > > >> > > >> > > >> Been there done that. Spent many weeks putting together a box that I was > > >> > > >> very proud of, then purchased a Rigol that does everything it does plus a > > >> > > >> lot more and a lot better. Is this really a good use of your time and > > >> > > >> energy? > > > > > >I get the point... and your are not the first one to tell me that. > > >but I believe that an oscilloscope is still an instruments a lot of electronic enthusiastic would love to have it if priced correctly. > > >Marketing will be the biggest challenge in a market so competitive. > > > > Did you look what a Siglent scope costs on Ebay? IIRC its about US > > $180 including shipping from China. How do you expect to beat that? > > BTW Lecroy sells the exact same scope for a lot more. > > > > -- > > Failure does not prove something is impossible, failure simply > > indicates you are not using the right tools... > > nico@nctdevpuntnl (punt=.) > > --------------------------------------------------------------
it's challenging but not impossible. I agree...It is very difficult to compete with China, but not impossible if we point on quality.
Francesco Poderico <francescopoderico@googlemail.com> wrote:

>On Sunday, 10 March 2013 16:35:29 UTC, Nico Coesel wrote: >> Francesco Poderico wrote: >> >> >> >> >> very proud of, then purchased a Rigol that does everything it does plus a >> >> lot more and a lot better. Is this really a good use of your time and >> >> energy? >> >> >I get the point... and your are not the first one to tell me that. >> >but I believe that an oscilloscope is still an instruments a lot of electronic enthusiastic would love to have it if priced correctly. >> >Marketing will be the biggest challenge in a market so competitive. >> >> Did you look what a Siglent scope costs on Ebay? IIRC its about US >> $180 including shipping from China. How do you expect to beat that? >> BTW Lecroy sells the exact same scope for a lot more. >> > >it's challenging but not impossible. > I agree...It is very difficult to compete with China, but not impossible if we point on quality.
If you think the Chinese can't make quality stuff then you've made your first big mistake. If its good enough for Lecroy to stick their badge on the quality bit is in order. So re-think your competitive edge. Remember that a good DSO is 5% hardware and 95% software. So even if you get the hardware right you are still nowhere near a sellable product. -- Failure does not prove something is impossible, failure simply indicates you are not using the right tools... nico@nctdevpuntnl (punt=.) --------------------------------------------------------------