On Fri, 08 Mar 2013 05:45:37 -0800, George Herold wrote:> My ‘scope is only 200MHz, so I’m not really sure I even believe the > 5ns... what’s that rule of thumb for ‘scope bandwidth/ rise time? tau= > 1/(3*BW) ?Very close. Tek always gave the formula: 0.35/BW ; it's based on the semi-mythical gaussian bandpass characteristic. If aberrations are significant, neither can be trusted. You probably know the formula for estimating risetime when the measurement approaches the instrument limits: tr= sqrt(tmeas^2 - tinstr^2) which of course only works when you already know that the pulses are clean - which you probably can't tell with that scope.
Simple pulse stretcher
Started by ●March 7, 2013
Reply by ●March 8, 20132013-03-08
Reply by ●March 8, 20132013-03-08
On Fri, 08 Mar 2013 06:54:50 -0800, John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:>On Fri, 08 Mar 2013 01:18:53 -0600, John Fields <jfields@austininstruments.com> >wrote: > >>On Thu, 07 Mar 2013 16:02:49 -0800, John Larkin >><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: >> >>>http://www.highlandtechnology.com/DSS/T240DS.shtml >> >>--- >>That's not a pulse stretcher, cheater, that's a pulse _generator_. > >It's a one-shot. It has no internal trigger. It generates no pulses.--- Geez, and here I always thought that one-shots generated waveforms with more-or-less crispy edges with a more-or less constant voltage level between them. You know, what we here in the real world call a "pulse". Take a look at the first bulleted item on your data sheet and you'll see that you do too, you fucking loon... -- JF
Reply by ●March 8, 20132013-03-08
On Fri, 8 Mar 2013 05:44:57 -0800 (PST), dagmargoodboat@yahoo.com wrote:>On Mar 8, 2:18�am, John Fields <jfie...@austininstruments.com> wrote: >> On Thu, 07 Mar 2013 16:02:49 -0800, John Larkin >> >> <jjlar...@highNOTlandTHIStechnologyPART.com> wrote: >> >http://www.highlandtechnology.com/DSS/T240DS.shtml >> >> --- >> That's not a pulse stretcher, cheater, that's a pulse _generator_. >> -- >> JF > >A *triggered* pulse generator.--- Yup; a "single-channel externally-triggered complementary-output pulse generator", from Larkin's blurb. -- JF
Reply by ●March 8, 20132013-03-08
On Friday, March 8, 2013 8:45:37 AM UTC-5, George Herold wrote:>=20 >=20 > My =91scope is only 200MHz, so I=92m not really sure I even believe the >=20 > 5ns... what=92s that rule of thumb for =91scope bandwidth/ rise time? tau==3D>=20 > 1/(3*BW) ? >=20Yes, assuming the probe is not a limitation. But the observed risetime is t= he RMS of signal + scope risetimes. http://cp.literature.agilent.com/litweb/pdf/5988-8008EN.pdf
Reply by ●March 8, 20132013-03-08
On Fri, 08 Mar 2013 11:08:42 -0600, John Fields <jfields@austininstruments.com> wrote:>On Fri, 08 Mar 2013 06:54:50 -0800, John Larkin ><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: > >>On Fri, 08 Mar 2013 01:18:53 -0600, John Fields <jfields@austininstruments.com> >>wrote: >> >>>On Thu, 07 Mar 2013 16:02:49 -0800, John Larkin >>><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: >>> >>>>http://www.highlandtechnology.com/DSS/T240DS.shtml >>> >>>--- >>>That's not a pulse stretcher, cheater, that's a pulse _generator_. >> >>It's a one-shot. It has no internal trigger. It generates no pulses. > >--- >Geez, and here I always thought that one-shots generated waveforms >with more-or-less crispy edges with a more-or less constant voltage >level between them. > >You know, what we here in the real world call a "pulse". > >Take a look at the first bulleted item on your data sheet and you'll >see that you do too, you fucking loon...More uninformed whining. All you want to do is argue about words, because you can't design electronics. You don't like any of my pulse stretchers, so design a better one. Post it here. Your great love Jim can do the same. -- John Larkin Highland Technology, Inc jlarkin at highlandtechnology dot com http://www.highlandtechnology.com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser drivers and controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation
Reply by ●March 8, 20132013-03-08
On Mar 8, 11:47=A0am, Frank Miles <f...@u.washington.edu> wrote:> On Fri, 08 Mar 2013 05:45:37 -0800, George Herold wrote: > > My =91scope is only 200MHz, so I=92m not really sure I even believe the > > 5ns... what=92s that rule of thumb for =91scope bandwidth/ rise time? t=au=3D> > 1/(3*BW) ? > > Very close. =A0Tek always gave the formula: 0.35/BW ; it's based on the > semi-mythical gaussian bandpass characteristic. =A0If aberrations are > significant, neither can be trusted. > > You probably know the formula for estimating risetime when the > measurement approaches the instrument limits:> =A0 =A0tr=3D sqrt(tmeas^2 - tinstr^2)No I didn't know that. Thanks, I guess mostly I like to have minimal instrumental effects :^) George H.> which of course only works when you already know that the pulses are > clean - which you probably can't tell with that scope.
Reply by ●March 8, 20132013-03-08
On Fri, 8 Mar 2013 16:47:58 +0000 (UTC), Frank Miles <fpm@u.washington.edu> wrote:>On Fri, 08 Mar 2013 05:45:37 -0800, George Herold wrote: > >> My �scope is only 200MHz, so I�m not really sure I even believe the >> 5ns... what�s that rule of thumb for �scope bandwidth/ rise time? tau= >> 1/(3*BW) ? > >Very close. Tek always gave the formula: 0.35/BW ; it's based on the >semi-mythical gaussian bandpass characteristic. If aberrations are >significant, neither can be trusted.That used to be true. The high-end digital scopes that I've tested lately don't seem to have gaussian response; they seem to be tweaked for bandwidth bragging rights, and subsequently ring. My "200 MHz" Tek DPO2024 rings a bit and has a rise time of 1.85 ns. -- John Larkin Highland Technology, Inc jlarkin at highlandtechnology dot com http://www.highlandtechnology.com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser drivers and controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation
Reply by ●March 8, 20132013-03-08
On 3/7/2013 2:36 PM, George Herold wrote:> On Mar 7, 3:12 pm, Vladimir Vassilevsky <nos...@nowhere.com> wrote: >> On 3/7/2013 12:21 PM, George Herold wrote: >> >>> Hi guys, I need a little digital pulse stretcher. I've got pulses >>> that are 5ns to 25ns in width, and I'd like to bump them all up to all >>> be at least 10ns. I've got a few spare 74HC14 inverters. I was >>> thinking of just feeding one through a diode followed by an R/C to >>> ground. Any other ways? There might be an extra AND gate too. >>> (not my circuit so I'm not quite sure.) >>>> Something like this: >> >> http://www.abvolt.com/misc/pulse_stretch.jpg >> >> You got the idea. >> > Yeah I was thinking of something like that too. The diode thing was > an easy 'hack' and seems to be working just fine. (I stuck in 10k > and 10pF and have about a 50ns minimum pulse.) Life is good.Fie. Analog parts on the digital board. http://www.abvolt.com/misc/pulse_stretch_2.jpg This should satisfy most captious critics. VLV
Reply by ●March 8, 20132013-03-08
On 3/8/2013 12:52 PM, George Herold wrote:> On Mar 8, 11:47 am, Frank Miles <f...@u.washington.edu> wrote: >> On Fri, 08 Mar 2013 05:45:37 -0800, George Herold wrote: >>> My �scope is only 200MHz, so I�m not really sure I even believe the >>> 5ns... what�s that rule of thumb for �scope bandwidth/ rise time? tau= >>> 1/(3*BW) ? >> >> Very close. Tek always gave the formula: 0.35/BW ; it's based on the >> semi-mythical gaussian bandpass characteristic. If aberrations are >> significant, neither can be trusted. >> >> You probably know the formula for estimating risetime when the >> measurement approaches the instrument limits: > >> tr= sqrt(tmeas^2 - tinstr^2) > No I didn't know that. Thanks, I guess mostly I like to have minimal > instrumental effects :^) > > George H. > >> which of course only works when you already know that the pulses are >> clean - which you probably can't tell with that scope. >It's actually more general than that--there's a Fourier transform theorem that variances add under convolution, so providing the pulse widths and rise times are defined in terms of the second moments, and there are no loading effects due to cascading the two devices, this formula works exactly. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 USA +1 845 480 2058 hobbs at electrooptical dot net http://electrooptical.net
Reply by ●March 8, 20132013-03-08
On Fri, 08 Mar 2013 09:46:41 -0800, John Larkin <jlarkin@highlandtechnology.com> wrote:>On Fri, 08 Mar 2013 11:08:42 -0600, John Fields ><jfields@austininstruments.com> wrote: > >>On Fri, 08 Mar 2013 06:54:50 -0800, John Larkin >><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: >> >>>On Fri, 08 Mar 2013 01:18:53 -0600, John Fields <jfields@austininstruments.com> >>>wrote: >>> >>>>On Thu, 07 Mar 2013 16:02:49 -0800, John Larkin >>>><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: >>>> >>>>>http://www.highlandtechnology.com/DSS/T240DS.shtml >>>> >>>>--- >>>>That's not a pulse stretcher, cheater, that's a pulse _generator_. >>> >>>It's a one-shot. It has no internal trigger. It generates no pulses. >> >>--- >>Geez, and here I always thought that one-shots generated waveforms >>with more-or-less crispy edges with a more-or less constant voltage >>level between them. >> >>You know, what we here in the real world call a "pulse". >> >>Take a look at the first bulleted item on your data sheet and you'll >>see that you do too, you fucking loon... > >More uninformed whining.--- Hey, you're the one with a data sheet touting your widget as a pulse generator, and I'm agreeing with it, so what's your problem? --->All you want to do is argue about words, because you can't design electronics.--- All you want to do is argue, about anything, in the vain hope that some miracle will come around when you've made a mistake - and it's been pointed out to you - and bail you out of the ocean of shit you get yourself into with that silly macho facade of infallibility. As for the "design" part, we've both seen my posting history, so we both know you're just having a hissie fit. --->You don't like any of my pulse stretchers, so design a better one.--- In your own words, they're not pulse stretchers, they're: "single-channel externally-triggered complementary-output pulse generator"(s). and, having had no experience with them, I neither like them nor dislike them. I would like to see some more data, though; Zout, maximum trigger rate, stuff like that... --->Post it here.--- Sorry Charlie; too much work for too little return. Especially when all you're looking for is something - anything - you can mouth off against and start another harangue to keep you in the limelight. --->Your great love Jim can do the same.--- Over the years, after a rocky beginning, I've come to appreciate Jim as a friend, a colleague, and a very clever circuit designer, and what love I have for him is fraternal. I don't think Jim will take your bait, but you invoke the malevolent accusation-of-homosexuality-with-no-basis-in-fact theme again? Seems like a flag you wave _way_ more often than necessary, Senator McCarthy. Early on, when you first started posting here, I felt some affection for you, but as time passed and your agenda crystallized it became apparent that your aim was nothing more than self-aggrandizement. I now feel nothing but contempt for you. -- JF
