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:
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.
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 ?
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???
I wouldn't. You're much better off getting something cheap, playing with it for awhile, and then -- if you're motivated to go further -- getting the high-end Fluke stuff.
No! It depends a lot on the scope, of course, but most don't want to see more than "some tens of volts" directly.
You can, of course, easily build yourself "high voltage" probe that are just resistive dividers.
x10 probes are actually used more to not load down the circuit being probe than to bring 240V->24V. This is done because heavy loading kills a circuit's frequency response -- the idea probe would have *no* influence on what was being measured, but a good approximation of this becomes difficult to do (especially *inexpensively*) when you start getting into the hundred MHz and up ballpark.
I've been impressed with these guys:
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-- they seem to have a solid understanding of what terms like "noise" and "jitter" mean, unlike many of the cheap scopes out there.
These guys:
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...are popular (they're one of the original players), but their performance seems a little lacking these days. In their older models, you couldn't sample both channels simultaneously (well, "chopped") without decimating the sampling rather either... uggh!
On a sunny day (Wed, 13 Dec 2006 13:27:01 -0600) it happened "news.valornet.com" wrote in :
No, that will likely destry teh scope.
I think not.
If the range is 20V / division with 8 divisions, then that scope _should_ be able to handle 160Vpp at least... But a 24V sinewave is already 2 x 24 x sqrt(2) = 68V pp, so watch out, and think in peak peak values always.
You could make your own, for less then a new digital scope,
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over to others to recommend stuff.
Or you could get a cheap analog one from ebay.
Forget the sound card scopes other then for monitoring sound....
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...
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).
Then these folks seem to include some scope functionality:
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I have poor impressions about these folks, but possibly unjustified:
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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@BOGUSsandia.gov
NOTE, delete texts: "RemoveThis" and
"BOGUS" from email address to reply.
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...
In my last job, in the early days of optical storage, we had at the lab an optical disk drive that wrote only to one kind of disk, 300MB or so, for $100/disk. I suggested we get one of the rather new, but well proven, cdrom drives that would write to 655MB cdroms at less than $1 each. But the drive would cost ~$300.
Damn near couldn't do it! They ordered $1000 of the old disks (easily accessible "consumable" funds), and dithered for months over whether to cut into "acquisition" funds for the cd writer.
Well I guess these things have their uses but you cant beat a real scope on so many levels. An old Tek can be had on ebay for peanuts and they work forever.
They've been around forever -- over a decade, I believe. I once had one of their "logic analyzer" boxes, and while it was nowhere near as feature-laden as a "real" logic analyzer, it was still useful and met its specs.
The only downside I recall was that they were quite slow to get drivers for new OSes (Windows 2000, at the time) out the door. The box I used was simple enough that I never had to call them up for support, so I can't comment on how they might fare there.
Hmm... I see on their main page they're advertising their DSO-8500 devices as spectrum analyzers. Probably not going to meet Joerg's wishlish with only
100MHz bandwidth and an 8 bit ADC (at 500Msps, so perhaps they effectively get
9 bits with oversampling), unfortunately.
The long number in that link is apparently a session ID that has expired, but searching for "Q1803" from dse.com.au gets you there.
Here in the U.S., I've seen same 'scope on eBay, e.g.,
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. It is rather cute and might make a lot of sense to keep around a lab for some quick troubleshooting, but for someone's first and only scope I really think the money would be better spent on a used Tek box.
I wonder how much storage tubes cost to manufacture? The Q1803 would probably have a lot more takers if it could freeze the trace so that it would work for troubleshooting, e.g., non-repetitive serial communications.
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