Are low/lower cost USB Oscilloscope's any good?
in [Design]
|
Prev: 74C925 alternative?
Next: 12 and 16-bit oscilloscopes
From: Joerg on 13 Dec 2006 18:13 Charlie Edmondson wrote: > Joerg wrote: > >> PeteS wrote: >> >>> Joerg wrote: >>> >>>> Hal Murray wrote: >>>> >>>>>> I've been impressed with these guys: http://www.cleverscope.com/ >>>>>> -- they seem to have a solid understanding of what terms like >>>>>> "noise" and "jitter" mean, unlike many of the cheap scopes out there. >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> A friend has one. He's very happy with it. >>>>> >>>>> One of the advantages of a PC based scope is that it doesn't take >>>>> up much room on your desktop. >>>>> >>>> >>>> But why are they so slow? At least the ones I have seen were. We >>>> designed 400MSPS converter boards even back in the late 80's and >>>> early 90's. It ain't rocket science. >>>> >>> >>> The company I work for doesn't have much of a budget for test >>> equipment, but we have a budget for boards (yeah I know) so I was >>> considering making a pretty fast scope / analyser using a quad set of >>> 500MS/s A-Ds and a couple of fast FPGAs and some memory. >>> >>> It won't be perfect, but it might do the job and save 'that budget'. >>> >> >> That's a strange way of looking at the financial bottomline. Look at >> the (realistic) number of paid hours you'll be working on that one-off >> project and then compare that to a nice used Tek scope. Now copy your >> boss on that. >> >> I have opted for the used Tek scope for my lab :-) >> > Back when I work at UC Santa Barbara, we had the same problem. Equipment > budgets needed to be approved, and were severely limited, so often it > was decided to build things rather than buy them. Why buy a $5000 > control system when you can get the parts for $500 and just have a guy > put it together and then go install it? > > The success story was the video distribution system for the campus. > Basically, it was a 16x256 channel switcher, with balance baseband > (6MHz) video on twinax, stereo sound and a two way intercom on each > channel. They built it in the 60s using RTL, and they were finally > going to start to replace it in 1993. The problem? They couldn't find > the RTL chips anymore for repairs, and some new buildings going in were > going to cut some of those custom multi-core twinax cables and they > couldn't replace or re-run them. The replacement would be on fiber. > > The horror story I was directly involved with. There was this one > building on campus that was basically four large lecture halls arranged > in a square, operated by a facility manager that had very specific goals > for any controls. He specified what the controllers would look like: It > had to be BIG (at least 3" x 9") and had to be HARD WIRED (so the > professors couldn't walk off with them!) The lighting control had to be > done with a pot, so you could pre-set your levels. The buttons needed > to be lighted and at least 1" square... > > Then, my boss got involved. He was an EE, and had been in charge of the > A/V maintanance dept before being promoted. He thought that touch tone > signalling would be just the thing, and directed one of the techs to > build the electronics. He directed another tech to run the cables for > the control. He then gave the cable tech a student helper (me!) to help > run the cables and install all the electical boxes. > > Note, of course, that none of these specifications were ever written > down. The cable guy dedided that a five conductor cable would be fine. > Power, TT control signal, ground, lighting control power, and the > lighting level signal. He then got the cable and ran it all over the > building. Approximate cost, counting his and my time - $2000. > > Then, the guy designing the electronics went on a bender, and never > built it, or even designed it! The cabling guy 'found other employment' > and the project needed to be passed on. So, they gave it to the new > student A/V design engineer - ME! > > First realization - five conductors weren't enough. The wires weren't > even twisted! The cabling guy was an electrician, and had decided that > audio didn't really need all that fancy twisting and stuff. So, > everything was going to share that one ground wire... > > I built the prototype, using parts lying around the place, and got it to > work. Only took me about 3 months, so only cost the department about > another $1000. Successfully demonstrated the prototype, installed it in > one of the lecture halls, and was given the go ahead to go into > production for the rest of the building. I designed the PC boards, but > when the EE department decided it would take 6 weeks to fab them, I was > put on to another project, and one of the techs was given the actual > installation duties. > > Of course, I made two big mistakes on the boards, so the tech had to > 'improvise' modifications. He built up the boards, tested them in the > lab, and started installing them. He put in the power supplies, mounted > and hooked up the boards, and powered them up. They worked for about > 2-6 hours, then died giving up magic smoke! > > After a week of trouble shooting ( the project was once again 'my baby') > I found the problem. I had originally used an off board +5 supply for > the electronics, but on redesign, had moved the 7805 onto the individual > boards. I had then specified 24 VDC supplies for the main power. When > installing the power supplies, the tech had found a whole bunch of > really nice unregulated 24 VDC supplies in a cabinet that he then > installed for the main power. However, since we were using only a tiny > fraction of the power needed, these supplies were a little overkill. > They were also 28 VDC supplies (for some cameras or something...) and > when unloaded, put out about 40 VDC. This overvoltage was cooking the > 7805's > > Finally, after about 3 years, the project was abandoned, and a real, > commercial system was installed. I figure the department spent between > $10K to $15K on trying to get that system to work. The commercial > system cost $4K. > > Yes, I spec'd and installed the commercial system! I was the 'official' > campus A/V engineer by that time! > Thanks for sharing that. Oh man! That sounds so familiar and was, in a nutshell, the reason why I left academia in a hurry the minute they handed me my masters degree. I designed a CCD camera plus matching VME interface as my masters project. From scratch because the commercial ones in the 80's were, well, sub-standard to say it politely. Their CCD array sampling circuits were mostly junk IMHO. It also had to work on a video system. The monitors at the university weren't great and since they wanted to determine the MTF of this new camera and all that to at least some level of precision we needed pro gear. I found a nice one at Barco but it was 2600 Deutschmarks. Slight problem: Anything past DM2000 needed the blessing of the King of Prussia and he had passed on a few hundred years ago. So, we convinced Barco to sell us a chassis for DM1900 and an enclosure for another DM700. And no, they didn't have to take it apart... -- Regards, Joerg http://www.analogconsultants.com
From: bill.sloman on 13 Dec 2006 18:31 Charlie Edmondson wrote: > Joerg wrote: > > > PeteS wrote: > > > >> Joerg wrote: > >> > >>> Hal Murray wrote: > >>> > >>>>> I've been impressed with these guys: http://www.cleverscope.com/ -- > >>>>> they seem to have a solid understanding of what terms like "noise" > >>>>> and "jitter" mean, unlike many of the cheap scopes out there. > >>>> > >>>> > >>>> > >>>> > >>>> A friend has one. He's very happy with it. > >>>> > >>>> One of the advantages of a PC based scope is that it doesn't take > >>>> up much room on your desktop. > >>>> > >>> > >>> But why are they so slow? At least the ones I have seen were. We > >>> designed 400MSPS converter boards even back in the late 80's and > >>> early 90's. It ain't rocket science. > >>> > >> > >> The company I work for doesn't have much of a budget for test > >> equipment, but we have a budget for boards (yeah I know) so I was > >> considering making a pretty fast scope / analyser using a quad set of > >> 500MS/s A-Ds and a couple of fast FPGAs and some memory. > >> > >> It won't be perfect, but it might do the job and save 'that budget'. > >> > > > > That's a strange way of looking at the financial bottomline. Look at the > > (realistic) number of paid hours you'll be working on that one-off > > project and then compare that to a nice used Tek scope. Now copy your > > boss on that. > > > > I have opted for the used Tek scope for my lab :-) > > > Back when I work at UC Santa Barbara, we had the same problem. > Equipment budgets needed to be approved, and were severely limited, so > often it was decided to build things rather than buy them. Why buy a > $5000 control system when you can get the parts for $500 and just have a > guy put it together and then go install it? > > The success story was the video distribution system for the campus. > Basically, it was a 16x256 channel switcher, with balance baseband > (6MHz) video on twinax, stereo sound and a two way intercom on each > channel. They built it in the 60s using RTL, and they were finally > going to start to replace it in 1993. The problem? They couldn't find > the RTL chips anymore for repairs, and some new buildings going in were > going to cut some of those custom multi-core twinax cables and they > couldn't replace or re-run them. The replacement would be on fiber. > > The horror story I was directly involved with. There was this one > building on campus that was basically four large lecture halls arranged > in a square, operated by a facility manager that had very specific goals > for any controls. He specified what the controllers would look like: It > had to be BIG (at least 3" x 9") and had to be HARD WIRED (so the > professors couldn't walk off with them!) The lighting control had to be > done with a pot, so you could pre-set your levels. The buttons needed > to be lighted and at least 1" square... > > Then, my boss got involved. He was an EE, and had been in charge of the > A/V maintanance dept before being promoted. He thought that touch tone > signalling would be just the thing, and directed one of the techs to > build the electronics. He directed another tech to run the cables for > the control. He then gave the cable tech a student helper (me!) to help > run the cables and install all the electical boxes. > > Note, of course, that none of these specifications were ever written > down. The cable guy dedided that a five conductor cable would be fine. > Power, TT control signal, ground, lighting control power, and the > lighting level signal. He then got the cable and ran it all over the > building. Approximate cost, counting his and my time - $2000. > > Then, the guy designing the electronics went on a bender, and never > built it, or even designed it! The cabling guy 'found other employment' > and the project needed to be passed on. So, they gave it to the new > student A/V design engineer - ME! > > First realization - five conductors weren't enough. The wires weren't > even twisted! The cabling guy was an electrician, and had decided that > audio didn't really need all that fancy twisting and stuff. So, > everything was going to share that one ground wire... > > I built the prototype, using parts lying around the place, and got it to > work. Only took me about 3 months, so only cost the department about > another $1000. Successfully demonstrated the prototype, installed it in > one of the lecture halls, and was given the go ahead to go into > production for the rest of the building. I designed the PC boards, but > when the EE department decided it would take 6 weeks to fab them, I was > put on to another project, and one of the techs was given the actual > installation duties. > > Of course, I made two big mistakes on the boards, so the tech had to > 'improvise' modifications. He built up the boards, tested them in the > lab, and started installing them. He put in the power supplies, mounted > and hooked up the boards, and powered them up. They worked for about > 2-6 hours, then died giving up magic smoke! > > After a week of trouble shooting ( the project was once again 'my baby') > I found the problem. I had originally used an off board +5 supply for > the electronics, but on redesign, had moved the 7805 onto the individual > boards. I had then specified 24 VDC supplies for the main power. When > installing the power supplies, the tech had found a whole bunch of > really nice unregulated 24 VDC supplies in a cabinet that he then > installed for the main power. However, since we were using only a tiny > fraction of the power needed, these supplies were a little overkill. > They were also 28 VDC supplies (for some cameras or something...) and > when unloaded, put out about 40 VDC. This overvoltage was cooking the > 7805's > > Finally, after about 3 years, the project was abandoned, and a real, > commercial system was installed. I figure the department spent between > $10K to $15K on trying to get that system to work. The commercial > system cost $4K. > > Yes, I spec'd and installed the commercial system! I was the 'official' > campus A/V engineer by that time! Wherever I've worked, rule one has always been, don't develop anything you can buy. Academics do have delusions about developing stuff in no time with no bugs, but university workshops know better. -- Bill Sloman, Nijmegen (but in Sydney at the moment).
From: Chris Carlen on 13 Dec 2006 18:39 news.valornet.com wrote: > Hi, > > I am just trying to mess around with electronics stuff, and I don't know too > much, but I've put a circuit or two together with help from this forum and > others. I've got a fluke DMM and clampmeter, but I'd really like to be able > to scope some stuff sometimes. I just don't know if I could part with the > money for a portable scope like a fluke 123 however just for playing around. > I have some questions and appreciate any suggestions for what might be good: > > 1. Do most scopes have decent voltage input on them? For example, can you > hook most of them up to line power (120vac or 240vac)? I am assuming the > fluke can do this no sweat, but I don't know. > > 2. I also see a bunch of references to X10 probes. Are these used to > reduce the voltage to something a scope can use, for example 240VAC --> > 24VAC ? > > 3. Do you have any recommendations for a scope that works on a notebook > that is relatively low cost that has decent features (keep in mind I have no > idea what features you would want in a scope). > > I would even consider some of these scopes that are free based ones that > work with a sound card, but my question is, what type of voltage input can > you get with a microphone jack??? > > Thanks! You're quite welcome. I'm surprized no one has yet mentioned Picoscope: http://www.picotech.com/ Then these folks seem to include some scope functionality: http://www.usbee.com I have poor impressions about these folks, but possibly unjustified: http://www.linkinstruments.com/ Note that there are benchtop (not PC based) digital scopes coming from various Chinese makers these days for ridiculously low prices. Also, Agilent and Tek are continuously extending the lower end of prices for brand name stuff. So you might prefer and be able to afford a benchtop unit, which can be more convenient. Then again, a PC based unit like the Picoscope can do some things that a bench scope can't. Higher resolution is one, long time period datalogging another. -- Good day! ________________________________________ Christopher R. Carlen Principal Laser&Electronics Technologist Sandia National Laboratories CA USA crcarleRemoveThis(a)BOGUSsandia.gov NOTE, delete texts: "RemoveThis" and "BOGUS" from email address to reply.
From: Charlie Edmondson on 13 Dec 2006 19:17 bill.sloman(a)ieee.org wrote: > Charlie Edmondson wrote: > >>Joerg wrote: >> >> >>>PeteS wrote: >>> >>> >>>>Joerg wrote: >>>> >>>> >>>>>Hal Murray wrote: >>>>> >>>>> >>>>>>>I've been impressed with these guys: http://www.cleverscope.com/ -- >>>>>>>they seem to have a solid understanding of what terms like "noise" >>>>>>>and "jitter" mean, unlike many of the cheap scopes out there. >>>>>> >>>>>> >>>>>> >>>>>> >>>>>>A friend has one. He's very happy with it. >>>>>> >>>>>>One of the advantages of a PC based scope is that it doesn't take >>>>>>up much room on your desktop. >>>>>> >>>>> >>>>>But why are they so slow? At least the ones I have seen were. We >>>>>designed 400MSPS converter boards even back in the late 80's and >>>>>early 90's. It ain't rocket science. >>>>> >>>> >>>>The company I work for doesn't have much of a budget for test >>>>equipment, but we have a budget for boards (yeah I know) so I was >>>>considering making a pretty fast scope / analyser using a quad set of >>>>500MS/s A-Ds and a couple of fast FPGAs and some memory. >>>> >>>>It won't be perfect, but it might do the job and save 'that budget'. >>>> >>> >>>That's a strange way of looking at the financial bottomline. Look at the >>>(realistic) number of paid hours you'll be working on that one-off >>>project and then compare that to a nice used Tek scope. Now copy your >>>boss on that. >>> >>>I have opted for the used Tek scope for my lab :-) >>> >> >>Back when I work at UC Santa Barbara, we had the same problem. >>Equipment budgets needed to be approved, and were severely limited, so >>often it was decided to build things rather than buy them. Why buy a >>$5000 control system when you can get the parts for $500 and just have a >>guy put it together and then go install it? >> >>The success story was the video distribution system for the campus. >>Basically, it was a 16x256 channel switcher, with balance baseband >>(6MHz) video on twinax, stereo sound and a two way intercom on each >>channel. They built it in the 60s using RTL, and they were finally >>going to start to replace it in 1993. The problem? They couldn't find >>the RTL chips anymore for repairs, and some new buildings going in were >>going to cut some of those custom multi-core twinax cables and they >>couldn't replace or re-run them. The replacement would be on fiber. >> >>The horror story I was directly involved with. There was this one >>building on campus that was basically four large lecture halls arranged >>in a square, operated by a facility manager that had very specific goals >>for any controls. He specified what the controllers would look like: It >>had to be BIG (at least 3" x 9") and had to be HARD WIRED (so the >>professors couldn't walk off with them!) The lighting control had to be >>done with a pot, so you could pre-set your levels. The buttons needed >>to be lighted and at least 1" square... >> >>Then, my boss got involved. He was an EE, and had been in charge of the >>A/V maintanance dept before being promoted. He thought that touch tone >>signalling would be just the thing, and directed one of the techs to >>build the electronics. He directed another tech to run the cables for >>the control. He then gave the cable tech a student helper (me!) to help >>run the cables and install all the electical boxes. >> >>Note, of course, that none of these specifications were ever written >>down. The cable guy dedided that a five conductor cable would be fine. >> Power, TT control signal, ground, lighting control power, and the >>lighting level signal. He then got the cable and ran it all over the >>building. Approximate cost, counting his and my time - $2000. >> >>Then, the guy designing the electronics went on a bender, and never >>built it, or even designed it! The cabling guy 'found other employment' >>and the project needed to be passed on. So, they gave it to the new >>student A/V design engineer - ME! >> >>First realization - five conductors weren't enough. The wires weren't >>even twisted! The cabling guy was an electrician, and had decided that >>audio didn't really need all that fancy twisting and stuff. So, >>everything was going to share that one ground wire... >> >>I built the prototype, using parts lying around the place, and got it to >>work. Only took me about 3 months, so only cost the department about >>another $1000. Successfully demonstrated the prototype, installed it in >>one of the lecture halls, and was given the go ahead to go into >>production for the rest of the building. I designed the PC boards, but >>when the EE department decided it would take 6 weeks to fab them, I was >>put on to another project, and one of the techs was given the actual >>installation duties. >> >>Of course, I made two big mistakes on the boards, so the tech had to >>'improvise' modifications. He built up the boards, tested them in the >>lab, and started installing them. He put in the power supplies, mounted >>and hooked up the boards, and powered them up. They worked for about >>2-6 hours, then died giving up magic smoke! >> >>After a week of trouble shooting ( the project was once again 'my baby') >>I found the problem. I had originally used an off board +5 supply for >>the electronics, but on redesign, had moved the 7805 onto the individual >>boards. I had then specified 24 VDC supplies for the main power. When >>installing the power supplies, the tech had found a whole bunch of >>really nice unregulated 24 VDC supplies in a cabinet that he then >>installed for the main power. However, since we were using only a tiny >>fraction of the power needed, these supplies were a little overkill. >>They were also 28 VDC supplies (for some cameras or something...) and >>when unloaded, put out about 40 VDC. This overvoltage was cooking the >>7805's >> >>Finally, after about 3 years, the project was abandoned, and a real, >>commercial system was installed. I figure the department spent between >>$10K to $15K on trying to get that system to work. The commercial >>system cost $4K. >> >>Yes, I spec'd and installed the commercial system! I was the 'official' >>campus A/V engineer by that time! > > > Wherever I've worked, rule one has always been, don't develop anything > you can buy. Academics do have delusions about developing stuff in no > time with no bugs, but university workshops know better. > Well, I have also seen the same sort of thing on the commercial side, too, where a boss didn't want to upset the budget apple cart to get something he felt the 'boys' should be able to just whip up out of teh parts room... Charlie
From: Phil Allison on 13 Dec 2006 19:28
"news.valornet.com" > > I am just trying to mess around with electronics stuff, and I don't know > too much, but I've put a circuit or two together with help from this forum > and others. I've got a fluke DMM and clampmeter, but I'd really like to > be able to scope some stuff sometimes. I just don't know if I could part > with the money for a portable scope like a fluke 123 however just for > playing around. I have some questions and appreciate any suggestions for > what might be good: > > 1. Do most scopes have decent voltage input on them? For example, can > you hook most of them up to line power (120vac or 240vac)? I am assuming > the fluke can do this no sweat, but I don't know. > > 2. I also see a bunch of references to X10 probes. Are these used to > reduce the voltage to something a scope can use, for example 240VAC --> > 24VAC ? > > 3. Do you have any recommendations for a scope that works on a notebook > that is relatively low cost that has decent features (keep in mind I have > no idea what features you would want in a scope). > > I would even consider some of these scopes that are free based ones that > work with a sound card, but my question is, what type of voltage input can > you get with a microphone jack??? > ** Maybe one of these is all you need. http://www.dse.com.au/cgi-bin/dse.storefront/45809b3e05c4671c2740c0a87f9c0727/Product/View/Q1803 ......... Phil |