Re: [time-nuts] OT - Portable Digital 'scope
Dale, Thanks for that. I'm still thinking about it - looks a fun bit of kit and as you say there is open source software available which is a plus. My other 'scope is a Tek 2465A by the way. Cheers Rob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Dale J. Robertson Sent: 23 February 2012 23:44 To: time-nuts@febo.com Subject: Re: [time-nuts] OT - Portable Digital 'scope I own one of these that I bought directly from Seeed Studios. Seeed also sells some very inexpensive MCX-BNC females for use with these as well as 1x-10x probes with mcx connectors. I have had their single channel version (DSO Nano) for a while and have found it handy. The DSO Quad has a considerably more complicated user interface. On the plus side the device is all open source and has several people developing software for it. This most definitely should NOT be your only oscilloscope. Dale NV8U On 2/23/2012 3:01 PM, Rob Kimberley wrote: I'm looking at Item: 300658066641 on EBay, and wanted to know if anyone in the group had any experience of this product. I know this is way off topic, but as a group it's nice to know what's out there and possibly useful in our mutual hobby. Thanks for reading. Rob Kimberley ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT - Portable Digital 'scope
Two things that jumps out is they have the schematic on the listing and the price. Thomas Knox From: robkimber...@btinternet.com To: time-nuts@febo.com Date: Thu, 23 Feb 2012 20:01:18 + Subject: [time-nuts] OT - Portable Digital 'scope I'm looking at Item: 300658066641 on EBay, and wanted to know if anyone in the group had any experience of this product. I know this is way off topic, but as a group it's nice to know what's out there and possibly useful in our mutual hobby. Thanks for reading. Rob Kimberley ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT - Portable Digital 'scope
Lots of info here http://www.seeedstudio.com/forum/index.php On 23.02.2012 14:01, Rob Kimberley wrote: I'm looking at Item: 300658066641 on EBay, and wanted to know if anyone in the group had any experience of this product. I know this is way off topic, but as a group it's nice to know what's out there and possibly useful in our mutual hobby. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT - Portable Digital 'scope
Looks interesting, but... 1) The probe connectors are not the usual BNC. Are they anything common? 2) No mating cables or connectors provided for channels 3,4, and function generator output. 3) Function generator output will have significant DC bias and no anti-aliasing. 4) Does not appear to be able to save files to a flash drive. 5) When connected to a PC the PC's earthing is carried through to the probes. No experience, sorry. Bob LaJeunesse From: Tom Knox act...@hotmail.com To: time-nuts@febo.com Sent: Thu, February 23, 2012 3:10:26 PM Subject: Re: [time-nuts] OT - Portable Digital 'scope Two things that jumps out is they have the schematic on the listing and the price. Thomas Knox From: robkimber...@btinternet.com To: time-nuts@febo.com Date: Thu, 23 Feb 2012 20:01:18 + Subject: [time-nuts] OT - Portable Digital 'scope I'm looking at Item: 300658066641 on EBay, and wanted to know if anyone in the group had any experience of this product. I know this is way off topic, but as a group it's nice to know what's out there and possibly useful in our mutual hobby. Thanks for reading. Rob Kimberley ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT - Portable Digital 'scope
Hi It looks like the connectors are MCX. It's a normal / low cost 50 ohm coax connector. You see them on some GPSDO's. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Robert LaJeunesse Sent: Thursday, February 23, 2012 3:32 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] OT - Portable Digital 'scope Looks interesting, but... 1) The probe connectors are not the usual BNC. Are they anything common? 2) No mating cables or connectors provided for channels 3,4, and function generator output. 3) Function generator output will have significant DC bias and no anti-aliasing. 4) Does not appear to be able to save files to a flash drive. 5) When connected to a PC the PC's earthing is carried through to the probes. No experience, sorry. Bob LaJeunesse From: Tom Knox act...@hotmail.com To: time-nuts@febo.com Sent: Thu, February 23, 2012 3:10:26 PM Subject: Re: [time-nuts] OT - Portable Digital 'scope Two things that jumps out is they have the schematic on the listing and the price. Thomas Knox From: robkimber...@btinternet.com To: time-nuts@febo.com Date: Thu, 23 Feb 2012 20:01:18 + Subject: [time-nuts] OT - Portable Digital 'scope I'm looking at Item: 300658066641 on EBay, and wanted to know if anyone in the group had any experience of this product. I know this is way off topic, but as a group it's nice to know what's out there and possibly useful in our mutual hobby. Thanks for reading. Rob Kimberley ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT - Portable Digital 'scope
On 2/23/2012 12:32 PM, Robert LaJeunesse wrote: Looks interesting, but... 1) The probe connectors are not the usual BNC. Are they anything common? 2) No mating cables or connectors provided for channels 3,4, and function generator output. 3) Function generator output will have significant DC bias and no anti-aliasing. 4) Does not appear to be able to save files to a flash drive. 5) When connected to a PC the PC's earthing is carried through to the probes. No experience, sorry. Bob LaJeunesse From: Tom Knoxact...@hotmail.com To: time-nuts@febo.com Sent: Thu, February 23, 2012 3:10:26 PM Subject: Re: [time-nuts] OT - Portable Digital 'scope Two things that jumps out is they have the schematic on the listing and the price. Thomas Knox From: robkimber...@btinternet.com To: time-nuts@febo.com Date: Thu, 23 Feb 2012 20:01:18 + Subject: [time-nuts] OT - Portable Digital 'scope I'm looking at Item: 300658066641 on EBay, and wanted to know if anyone in the group had any experience of this product. I know this is way off topic, but as a group it's nice to know what's out there and possibly useful in our mutual hobby. Thanks for reading. Rob Kimberley ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. Ch's C D are on other side. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT - Portable Digital 'scope
On Thu, 23 Feb 2012 20:01:18 - Rob Kimberley robkimber...@btinternet.com wrote: I'm looking at Item: 300658066641 on EBay, and wanted to know if anyone in the group had any experience of this product. I know this is way off topic, but as a group it's nice to know what's out there and possibly useful in our mutual hobby. It depends what you want to use it for. If you just want to have something protable that can show you roughly what's going on, then this might be a good thing. For anything else, especially measurements, i wouldnt trust it further than i can throw it. It's actually quite nice that they put the schematics online too, so their claims can be verified. First that jumps out is that they are using a AD9288-40 as ADC. Note the -40 there? It means it's an 40Msps ADC. Ie the maximum usable BW you can have is 20MHz (actually a bit lower). The analog circuitry doesn't seem too bright either, but i guess you should be able to get the 20MHz. I havent checked the exact circuitry so i cannot say whether the input circuit does filter at 20MHz. But as they claim to have 72MHz analog bandwidth, i would be very carefull about aliasing problems The input circuitry isn't very impressive either and has an undefined input capacitance (there is a trimmer there) somwhere between 5pF and 30pF (plus stray capacitances). I find it a it strange, that they disconnect one input of the frontend opamp... it might anything from going into saturation to start bouncing around... The analog switches are rather on the cheap side, nothing you'd expect in an DSO, but well.. for that price :-) Also notice that the connectors used look like SMB or MCX antenna connectors. Ie those would not be able to withstand many mating/break cycles. Overall, i'd say a good portable gauge, but not much more. For a more indepth analysis i'd have to take the schematics apart into a readable format... Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT - Portable Digital 'scope
FWIW Rigol pushes their 40MHz Analog Devices part to 100 MHz without any problem (seen in eevblog teardown). Yes it's sort of cheating, but if the part works fine because all of the suppliers parts now yeild that fast due to an improved process well, it saves a few dollars / quid / drachma... And the 40MSPS is over full temp range, likely this is not a problem for the DSO 203 which has NO temp rating. Yes the 72MHz analog channel rating makes no sense for something sampling at 72MSPS, Nyquist says you get at most 36 MHz bandwith. I saw no anti-aliasing filter (well, C9 or C11 and C73 do some roll off) so who knows what the screen will actually show. Might make a decent 10MHz scope, at which point the use of FET solid-state relays doesn't concern me so much. I was surprised that they use trimmers on the input to match the channels, that's a nice touch but does add some loading. The U1B op-amp is disconnected for higher input voltage ranges so it doesn't overload and distort the signal, which is processed by the U1A amp for those ranges. Perhaps not good that the U1B input is left effectively floating. Bob LaJeunesse From: Attila Kinali att...@kinali.ch To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Thu, February 23, 2012 3:49:49 PM Subject: Re: [time-nuts] OT - Portable Digital 'scope On Thu, 23 Feb 2012 20:01:18 - Rob Kimberley robkimber...@btinternet.com wrote: I'm looking at Item: 300658066641 on EBay, and wanted to know if anyone in the group had any experience of this product. I know this is way off topic, but as a group it's nice to know what's out there and possibly useful in our mutual hobby. It depends what you want to use it for. If you just want to have something protable that can show you roughly what's going on, then this might be a good thing. For anything else, especially measurements, i wouldnt trust it further than i can throw it. It's actually quite nice that they put the schematics online too, so their claims can be verified. First that jumps out is that they are using a AD9288-40 as ADC. Note the -40 there? It means it's an 40Msps ADC. Ie the maximum usable BW you can have is 20MHz (actually a bit lower). The analog circuitry doesn't seem too bright either, but i guess you should be able to get the 20MHz. I havent checked the exact circuitry so i cannot say whether the input circuit does filter at 20MHz. But as they claim to have 72MHz analog bandwidth, i would be very carefull about aliasing problems The input circuitry isn't very impressive either and has an undefined input capacitance (there is a trimmer there) somwhere between 5pF and 30pF (plus stray capacitances). I find it a it strange, that they disconnect one input of the frontend opamp... it might anything from going into saturation to start bouncing around... The analog switches are rather on the cheap side, nothing you'd expect in an DSO, but well.. for that price :-) Also notice that the connectors used look like SMB or MCX antenna connectors. Ie those would not be able to withstand many mating/break cycles. Overall, i'd say a good portable gauge, but not much more. For a more indepth analysis i'd have to take the schematics apart into a readable format... Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT - Portable Digital 'scope
Yes, in my opinion the connectors are MCX and I totally agree with Attila about the 20MHz limit. Nice toy to just take a look at low speed signals, for example GPSDOs 10MHz and PPS, serial lines and so on. On Thu, Feb 23, 2012 at 9:49 PM, Attila Kinali att...@kinali.ch wrote: On Thu, 23 Feb 2012 20:01:18 - Rob Kimberley robkimber...@btinternet.com wrote: I'm looking at Item: 300658066641 on EBay, and wanted to know if anyone in the group had any experience of this product. I know this is way off topic, but as a group it's nice to know what's out there and possibly useful in our mutual hobby. It depends what you want to use it for. If you just want to have something protable that can show you roughly what's going on, then this might be a good thing. For anything else, especially measurements, i wouldnt trust it further than i can throw it. It's actually quite nice that they put the schematics online too, so their claims can be verified. First that jumps out is that they are using a AD9288-40 as ADC. Note the -40 there? It means it's an 40Msps ADC. Ie the maximum usable BW you can have is 20MHz (actually a bit lower). The analog circuitry doesn't seem too bright either, but i guess you should be able to get the 20MHz. I havent checked the exact circuitry so i cannot say whether the input circuit does filter at 20MHz. But as they claim to have 72MHz analog bandwidth, i would be very carefull about aliasing problems The input circuitry isn't very impressive either and has an undefined input capacitance (there is a trimmer there) somwhere between 5pF and 30pF (plus stray capacitances). I find it a it strange, that they disconnect one input of the frontend opamp... it might anything from going into saturation to start bouncing around... The analog switches are rather on the cheap side, nothing you'd expect in an DSO, but well.. for that price :-) Also notice that the connectors used look like SMB or MCX antenna connectors. Ie those would not be able to withstand many mating/break cycles. Overall, i'd say a good portable gauge, but not much more. For a more indepth analysis i'd have to take the schematics apart into a readable format... Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT - Portable Digital 'scope
On 2/23/12 1:25 PM, Robert LaJeunesse wrote: FWIW Rigol pushes their 40MHz Analog Devices part to 100 MHz without any problem (seen in eevblog teardown). Yes it's sort of cheating, but if the part works fine because all of the suppliers parts now yeild that fast due to an improved process well, it saves a few dollars / quid / drachma... And the 40MSPS is over full temp range, likely this is not a problem for the DSO 203 which has NO temp rating. Yes the 72MHz analog channel rating makes no sense for something sampling at 72MSPS, Nyquist says you get at most 36 MHz bandwith. That doesn't mean you couldn't use a sampler running at, say, 50 MSPS to look at a 110 MHz signal (something we actually do in a radio). There are lots of ADCs out there that have RF bandwidths of much more than the sample rate, intended for use in direct sampling receivers. What performance really depends on is how good the sample/hold or track/hold is and what the sample jitter is. (and of course, whether there's a stage in front to keep unexpected signals from aliasing in) There are several ADCs out there that have GHz bandwidths and max sample rates in the 100MSPS range. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT - Portable Digital 'scope
Actually, undersampling does use the alias effect to bring down the RF carrier. That is, the direct sampling radio concept cannot avoid the aliasing: it is exploited to avoid, for example, to sample a 2GHz carrier modulated with a 20MHz signal with a 4Gsample/second ADC (by the way, does it exist?). A simple 20Msample/second ADC would be enough. Yes, to analyze an analog signal in real time I doubt you can use this method, if the signal is periodic maybe... you can advance the sampling trigger a bit, cycle by cycle, and reconstruct the whole signal after this little amount has covered a full cycle. On Thu, Feb 23, 2012 at 10:56 PM, Jim Lux jim...@earthlink.net wrote: On 2/23/12 1:25 PM, Robert LaJeunesse wrote: FWIW Rigol pushes their 40MHz Analog Devices part to 100 MHz without any problem (seen in eevblog teardown). Yes it's sort of cheating, but if the part works fine because all of the suppliers parts now yeild that fast due to an improved process well, it saves a few dollars / quid / drachma... And the 40MSPS is over full temp range, likely this is not a problem for the DSO 203 which has NO temp rating. Yes the 72MHz analog channel rating makes no sense for something sampling at 72MSPS, Nyquist says you get at most 36 MHz bandwith. That doesn't mean you couldn't use a sampler running at, say, 50 MSPS to look at a 110 MHz signal (something we actually do in a radio). There are lots of ADCs out there that have RF bandwidths of much more than the sample rate, intended for use in direct sampling receivers. What performance really depends on is how good the sample/hold or track/hold is and what the sample jitter is. (and of course, whether there's a stage in front to keep unexpected signals from aliasing in) There are several ADCs out there that have GHz bandwidths and max sample rates in the 100MSPS range. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT - Portable Digital 'scope
On Thu, Feb 23, 2012 at 2:22 PM, Azelio Boriani azelio.bori...@screen.itwrote: Actually, undersampling does use the alias effect to bring down the RF carrier. That is, the direct sampling radio concept cannot avoid the aliasing: it is exploited to avoid, for example, to sample a 2GHz carrier modulated with a 20MHz signal with a 4Gsample/second ADC (by the way, does it exist?). A simple 20Msample/second ADC would be enough. Yes, to analyze an analog signal in real time I doubt you can use this method, if the signal is periodic maybe... you can advance the sampling trigger a bit, cycle by cycle, and reconstruct the whole signal after this little amount has covered a full cycle. Yes. See for example, the description on this (and the seller's other similar) ebay item(s): 260955742514 Orin. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT - Portable Digital 'scope
On 2/23/12 2:22 PM, Azelio Boriani wrote: Actually, undersampling does use the alias effect to bring down the RF carrier. That is, the direct sampling radio concept cannot avoid the aliasing: it is exploited to avoid, for example, to sample a 2GHz carrier modulated with a 20MHz signal with a 4Gsample/second ADC (by the way, does it exist?). A simple 20Msample/second ADC would be enough. Well.. a 40 MSPS ADC for a 20 MHz wide signal, but yes. There *are* multi Gsample/second ADCs out there. ADC12D1800, 12 bit, 3.6 GSPS. ADS5400 12 bit 1GSPS etc Yes, to analyze an analog signal in real time I doubt you can use this method, if the signal is periodic maybe... you can advance the sampling trigger a bit, cycle by cycle, and reconstruct the whole signal after this little amount has covered a full cycle. That's the way the sampling head used for microwaves works (back in the day, when tunnel diodes were a new and exotic thing, for instance). Still used to today on scopes where they call it things like equivalent time sampling... basically a real fast sample and hold, and a not so fast ADC. There's also clever schemes with fast S/H and multiple interleaved ADCs.. but accounting for the tracking errors between ADCs is always a chore. And, various sub-band-coding approaches where you subdivide the frequency into sub-bands, digitize them in parallel and do fancy math to recombine it into a single stream of samples. If the channelization and ADC clocks are cleverly chosen and derived from the same reference, you can do quite well ( compensate for differences among ADCs) The high performance radar processing world is full of this kind of thing (look up STAP: space/time adaptive processing). ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT - Portable Digital 'scope
Sampling oscilloscopes and digital storage oscilloscopes that support equivalent time sampling do this very thing. My Tektronix 2230 with a 20 MS/sec flash converter has a bandwidth of 100 MHz and a 2 GS/sec equivalent time sampling rate. A 7854 with a 500 kS/sec sampler (at 10 or 11 bits) and is good to at least 400 MHz. A 7T11 samples at 50 kS/sec but has a 14 GHz bandwidth with an S-4 sampling head. All of the above examples rely on repetitive signals and use one or another form of time to voltage conversion. The 2230 directly measures the time difference between the trigger and sample clock with a time to voltage converter. The 7854 simultaneously samples the signal and the sweep. The 7T11 sequentially or randomly triggers the sampler at different sweep positions. The DS203 is relying on digital triggering after the ADC so equivalent time sampling is possible but subject to aliasing of the reconstructed trigger waveform itself. I presume each acquisition record is aligned with the waveform record before being merged. Some more recent high performance DSOs work this way. On Thu, 23 Feb 2012 23:22:01 +0100, Azelio Boriani azelio.bori...@screen.it wrote: Actually, undersampling does use the alias effect to bring down the RF carrier. That is, the direct sampling radio concept cannot avoid the aliasing: it is exploited to avoid, for example, to sample a 2GHz carrier modulated with a 20MHz signal with a 4Gsample/second ADC (by the way, does it exist?). A simple 20Msample/second ADC would be enough. Yes, to analyze an analog signal in real time I doubt you can use this method, if the signal is periodic maybe... you can advance the sampling trigger a bit, cycle by cycle, and reconstruct the whole signal after this little amount has covered a full cycle. On Thu, Feb 23, 2012 at 10:56 PM, Jim Lux jim...@earthlink.net wrote: On 2/23/12 1:25 PM, Robert LaJeunesse wrote: FWIW Rigol pushes their 40MHz Analog Devices part to 100 MHz without any problem (seen in eevblog teardown). Yes it's sort of cheating, but if the part works fine because all of the suppliers parts now yeild that fast due to an improved process well, it saves a few dollars / quid / drachma... And the 40MSPS is over full temp range, likely this is not a problem for the DSO 203 which has NO temp rating. Yes the 72MHz analog channel rating makes no sense for something sampling at 72MSPS, Nyquist says you get at most 36 MHz bandwith. That doesn't mean you couldn't use a sampler running at, say, 50 MSPS to look at a 110 MHz signal (something we actually do in a radio). There are lots of ADCs out there that have RF bandwidths of much more than the sample rate, intended for use in direct sampling receivers. What performance really depends on is how good the sample/hold or track/hold is and what the sample jitter is. (and of course, whether there's a stage in front to keep unexpected signals from aliasing in) There are several ADCs out there that have GHz bandwidths and max sample rates in the 100MSPS range. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT - Portable Digital 'scope
Actually, undersampling does use the alias effect to bring down the RF carrier. That is, the direct sampling radio concept cannot avoid the aliasing: it is exploited to avoid, for example, to sample a 2GHz carrier modulated with a 20MHz signal with a 4Gsample/second ADC (by the way, does it exist?). A simple 20Msample/second ADC would be enough... The trick is that Nyquist still holds. You can capture a 1 GHz signal with a 40 MHz ADC as long as the signal bandwidth is only 20 MHz. It may get tricky to build an anti-aliasing filter with those parameters. As Jim said, the analog front end and sample-hold needs the raw bandwidth and the clock driving the sample-hold needs good accuracy. -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT - Portable Digital 'scope
I own one of these that I bought directly from Seeed Studios. Seeed also sells some very inexpensive MCX-BNC females for use with these as well as 1x-10x probes with mcx connectors. I have had their single channel version (DSO Nano) for a while and have found it handy. The DSO Quad has a considerably more complicated user interface. On the plus side the device is all open source and has several people developing software for it. This most definitely should NOT be your only oscilloscope. Dale NV8U On 2/23/2012 3:01 PM, Rob Kimberley wrote: I'm looking at Item: 300658066641 on EBay, and wanted to know if anyone in the group had any experience of this product. I know this is way off topic, but as a group it's nice to know what's out there and possibly useful in our mutual hobby. Thanks for reading. Rob Kimberley ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT - Portable Digital 'scope
Switched gain stages mean the bandwidth and transient response before the ADC is going to change with different sensitivities unless both are significantly limited which apparently is the case. How do modern DSOs handle that? I guess it would explain why I have been told their front end calibration is so arduous. If you lose the calibration constants somehow, you might as well throw the oscilloscope away. Do any support user recalibration? I agree that the floating input is a problem. Maybe they got lucky with that specific operational amplifier. On Thu, 23 Feb 2012 13:25:51 -0800 (PST), Robert LaJeunesse rlajeune...@sbcglobal.net wrote: FWIW Rigol pushes their 40MHz Analog Devices part to 100 MHz without any problem (seen in eevblog teardown). Yes it's sort of cheating, but if the part works fine because all of the suppliers parts now yeild that fast due to an improved process well, it saves a few dollars / quid / drachma... And the 40MSPS is over full temp range, likely this is not a problem for the DSO 203 which has NO temp rating. Yes the 72MHz analog channel rating makes no sense for something sampling at 72MSPS, Nyquist says you get at most 36 MHz bandwith. I saw no anti-aliasing filter (well, C9 or C11 and C73 do some roll off) so who knows what the screen will actually show. Might make a decent 10MHz scope, at which point the use of FET solid-state relays doesn't concern me so much. I was surprised that they use trimmers on the input to match the channels, that's a nice touch but does add some loading. The U1B op-amp is disconnected for higher input voltage ranges so it doesn't overload and distort the signal, which is processed by the U1A amp for those ranges. Perhaps not good that the U1B input is left effectively floating. From: Attila Kinali att...@kinali.ch To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Thu, February 23, 2012 3:49:49 PM Subject: Re: [time-nuts] OT - Portable Digital 'scope On Thu, 23 Feb 2012 20:01:18 - Rob Kimberley robkimber...@btinternet.com wrote: I'm looking at Item: 300658066641 on EBay, and wanted to know if anyone in the group had any experience of this product. I know this is way off topic, but as a group it's nice to know what's out there and possibly useful in our mutual hobby. It depends what you want to use it for. If you just want to have something protable that can show you roughly what's going on, then this might be a good thing. For anything else, especially measurements, i wouldnt trust it further than i can throw it. It's actually quite nice that they put the schematics online too, so their claims can be verified. First that jumps out is that they are using a AD9288-40 as ADC. Note the -40 there? It means it's an 40Msps ADC. Ie the maximum usable BW you can have is 20MHz (actually a bit lower). The analog circuitry doesn't seem too bright either, but i guess you should be able to get the 20MHz. I havent checked the exact circuitry so i cannot say whether the input circuit does filter at 20MHz. But as they claim to have 72MHz analog bandwidth, i would be very carefull about aliasing problems The input circuitry isn't very impressive either and has an undefined input capacitance (there is a trimmer there) somwhere between 5pF and 30pF (plus stray capacitances). I find it a it strange, that they disconnect one input of the frontend opamp... it might anything from going into saturation to start bouncing around... The analog switches are rather on the cheap side, nothing you'd expect in an DSO, but well.. for that price :-) Also notice that the connectors used look like SMB or MCX antenna connectors. Ie those would not be able to withstand many mating/break cycles. Overall, i'd say a good portable gauge, but not much more. For a more indepth analysis i'd have to take the schematics apart into a readable format... Attila Kinali ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT - Portable Digital 'scope
If the bandwidth is really limited to 2 MHz, that is a rise and fall time of 175ns. Some of those PPS signals are barely wider than that. On Thu, 23 Feb 2012 22:26:47 +0100, Azelio Boriani azelio.bori...@screen.it wrote: Yes, in my opinion the connectors are MCX and I totally agree with Attila about the 20MHz limit. Nice toy to just take a look at low speed signals, for example GPSDOs 10MHz and PPS, serial lines and so on. On Thu, Feb 23, 2012 at 9:49 PM, Attila Kinali att...@kinali.ch wrote: On Thu, 23 Feb 2012 20:01:18 - Rob Kimberley robkimber...@btinternet.com wrote: I'm looking at Item: 300658066641 on EBay, and wanted to know if anyone in the group had any experience of this product. I know this is way off topic, but as a group it's nice to know what's out there and possibly useful in our mutual hobby. It depends what you want to use it for. If you just want to have something protable that can show you roughly what's going on, then this might be a good thing. For anything else, especially measurements, i wouldnt trust it further than i can throw it. It's actually quite nice that they put the schematics online too, so their claims can be verified. First that jumps out is that they are using a AD9288-40 as ADC. Note the -40 there? It means it's an 40Msps ADC. Ie the maximum usable BW you can have is 20MHz (actually a bit lower). The analog circuitry doesn't seem too bright either, but i guess you should be able to get the 20MHz. I havent checked the exact circuitry so i cannot say whether the input circuit does filter at 20MHz. But as they claim to have 72MHz analog bandwidth, i would be very carefull about aliasing problems The input circuitry isn't very impressive either and has an undefined input capacitance (there is a trimmer there) somwhere between 5pF and 30pF (plus stray capacitances). I find it a it strange, that they disconnect one input of the frontend opamp... it might anything from going into saturation to start bouncing around... The analog switches are rather on the cheap side, nothing you'd expect in an DSO, but well.. for that price :-) Also notice that the connectors used look like SMB or MCX antenna connectors. Ie those would not be able to withstand many mating/break cycles. Overall, i'd say a good portable gauge, but not much more. For a more indepth analysis i'd have to take the schematics apart into a readable format... Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT - Portable Digital 'scope
On Thu, 23 Feb 2012 17:53:49 -0600 David davidwh...@gmail.com wrote: How do modern DSOs handle that? I guess it would explain why I have been told their front end calibration is so arduous. If you lose the calibration constants somehow, you might as well throw the oscilloscope away. Do any support user recalibration? There are lots of companies offering oscilloscope callibration. But it's damn expensive. For the 1Gsps oscilloscope we have at work, it costs around 2000 CHF IIRC. And those beasts have to be callibrated every two years (if we'd do qualification measurments, that would be even more often). Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT - Portable Digital 'scope
Ops, yes, 2MHz is a little narrow. 20MHz is better... On Fri, Feb 24, 2012 at 1:28 AM, Attila Kinali att...@kinali.ch wrote: On Thu, 23 Feb 2012 17:53:49 -0600 David davidwh...@gmail.com wrote: How do modern DSOs handle that? I guess it would explain why I have been told their front end calibration is so arduous. If you lose the calibration constants somehow, you might as well throw the oscilloscope away. Do any support user recalibration? There are lots of companies offering oscilloscope callibration. But it's damn expensive. For the 1Gsps oscilloscope we have at work, it costs around 2000 CHF IIRC. And those beasts have to be callibrated every two years (if we'd do qualification measurments, that would be even more often). Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
