Cheap PC Oscilloscopes - Any Recommendations?

Missionary Man asks: "I'm an electronics teacher looking for a good (but reasonably cheap) PC based oscilloscope for classroom demonstration purposes. I've done a reasonable amount of research and come up with a few contenders. Ideally I'd like something with a bandwidth of up to 40MHz and 2 channels. Does anyone have any tales to tell regarding the use of any of these scopes (or any others I haven't found or mentioned) and can recommend a suitable device?"

"Here's the list of my findings so far:

• The DS2200C from USB Instruments will do 2 channels at 12 bit resolution, but only to 200KHz.
• The PCS100 from Velleman at QKits runs to 12MHz, but only 1 channel. It has a bigger brother, the PCS500, that has 2 channels and 50MHz bandwidth, but is a lot more expensive.
• Picotech do cheaper ones, like the ADC-40/42, but these only operate in the KHz ranges.
• Link Instruments sell the DSO-2102S that runs to 60MHz with 2 channels, but it's a bit out of my price range.
• Finally, I found the bitscope which seems to be just what I'm looking for, combining a 2 channel scope and an 8 channel logic analyzer for a reasonable price.

I'm hoping to spend US$300-$400. I recognize the software is a fundamental part of the successful operation of these units and any comments regarding the bundled programs would be most helpful too!"

Comments

Some places to check out...

[lukewarmfusion]

I see them on case modding sites occasionally. As far as your use, I'm not sure how they would measure up. Knowing the thriftiness of many modders, you may be able to find a decent recommendation there.

Here's one to check out -Price page is unreachable

[MikeDawg]

Check this one out. . . I don't know the price because their price page is broken. . . It looks like everything you need in a PC Oscillioscope.

winamp?

[VegetariMan]

I think my media player has an oscilloscope...

Re:winamp?

[Anonymous Coward]

That brings up an interesting question. Could a circuit be devised that would take an external frequency outside of hearing range, and enable it to be fed into the audio input of a soundcard, so a media player's oscilloscope would work?

Re:winamp?

[seanadams.com]

You know, for classroom demonstrations a sound card should be perfectly acceptable for all kinds of things... especially considering that there is also very nice free spectrum analyzer software available. On top of that, students can easily repeat experiments on their systems at home. Of course with a max sampling rate of 48KHz there's only so much you can do, but low speed osciallators, R/C circuits, switching power supplies and all sorts of things can still be seen to a useful extent.

Re:winamp?

[FredGray]

You know, for classroom demonstrations a sound card should be perfectly acceptable for all kinds of things...

My understanding is that sound card inputs are AC coupled, so you won't be able to see anything much slower than about 20 Hz. That might be OK, but it's not quite an oscilloscope.

Re:winamp?

[seanadams.com]

Good point... I think you could probably address that by bypassing the cap on the input, but then your "zero" level would probably be 1.15V.

Re:winamp?

[unitron]

Beat it against a local oscillator set to a frequency such that the difference of the two lands between zero and 20 thousand cycles per second (Hz). It's called heterodyning and has been used to shift frequencies since the early days of radio if not before.

Re:winamp?

[kiatoa]

Could a circuit be devised that would take an external frequency outside of hearing range, and enable it to be fed into the audio input of a soundcard, so a media player's oscilloscope would work?

A sample-hold should do it. Run the sample-hold at the same frequency that you are running the sound card sampling. Essentially you fold the higher frequencies into the sound cards range and since you are doing an ocilloscope you use software to offset each cycle of sampling and build up your picture of a cycle over several cycles. By the time you had that all figured out you'd be better off with the scope card and software. Especially since the sound card won't do DC-30Hz. Interesting idea though.

Re:winamp?

[p3tersen]

You can do all kinds of cool things! At my old university we taught a second year physics laboratory in which the students measured the johnson noise temperature of a resistor using a low-noise amplifier plugged into the mic port of the old imacs in the lab. The amplifier transfer functions were determined by feeding the LNA's white noise from the headphone jack! I thought it was such a cool idea to use the sound card in this way.

Re:winamp?

[keeboo]

plus i don't know any "winamp-like osciloscope" that stabilizes the waveform.. so what you see is not a pretty standing waveform but something chaotic and not really useful.

not mentioning that you don't have the V measurement (ok.. i guess you can write in the monitor using a soft pen ;)

since the guy is mentioning software i assume he doesn't feel (or is not able to) write one himself, so the soundcard option is not a good option for him.

Re:winamp?

[Rebar]

Depends on the size of the capacitors on the input side of the sound card - the larger the RC time constant, the lower the frequency signal that can be observed. My old SB compatible card could pick up as low as 3hz signals really easily - I had an animometer hooked directly to it and counted zero-crossings to determine the wind speed. The signal may not be that linear under 20hz, but it's still really easy to see.

I agree with the parent post about a sound card being a nice classroom demonstration scope. For higher mhz, you can pick up a real scope from Ebay for much cheaper than a PC card solution.

Re:winamp?

[tftp]

You described a stroboscopic (sampling) oscilloscope. However it has a serious, theoretical flaw - the bandwidth of the signal is still limited to the 20 kHz that the sound card can take in.

What you are doing is basically undersampling the incoming signal and then assuming that the original falls into one of many aliases that the undersampling generated.

In other words, if the signal changes while you are sampling and reconstructing it, the change is lost and results in incorrect reconstruction.

The original poster's question assumes that the PC-based scope is the best solution to his problem. My EE experience tells me that generally you want a standalone scope (you want as many screens as you can get, space be damned.) Teacher's needs, of course, may benefit from the PC-based scope (multicasting the readings to students' computers, for one.)

Re:winamp?

[Anonymous Coward]

what you can do is make an 'audio chopper'(easy to make.. see google). get the DC from your electronics and reverse polarity every 1KHz from the DC to make it AC. software can then reconstruct the original DC signal. Works ok (minus some chirps every 1KHz)...

Bankruptcy Auctions!

[Supp0rtLinux]

Search google for bankruptcy auctions. I'm sure you can find what you're looking for. I work for a biotech that saved 75% of our initial budget by acquiring medical laboratory supplies from six other biotechs that went bankrupt in recent months. We did such a good job, our VC company gave us more than we asked for to buy the rest of what we needed.

The only thing necessary for Micro$oft to triumph is for a few good programmers to do nothing". North County Computers

Re:Bankruptcy Auctions!

[bigberk]

I work for a biotech that saved 75% of our initial budget by acquiring medical laboratory supplies from six other biotechs that went bankrupt in recent months

Six others? OMG, and that didn't in the least suggest to you that maybe you're in the wrong kind of business?

Re:Bankruptcy Auctions!

[Supp0rtLinux]

Check out our business - www.genvault.com. We aren't going anywhere. We're the future of DNA storage. We have medical and biotech companies beating down our doors. GenVault

The only thing necessary for Micro$oft to triumph is for a few good programmers to do nothing". North County Computers

Re:Bankruptcy Auctions!

[The Clockwork Troll]

Six others? OMG, and that didn't in the least suggest to you that maybe you're in the wrong kind of business?

How many IT companies have gone out of business in recent years? Does that dictate that the upstart firms with financial discipline and valuable products/services should pack up shop and close their doors? Because it's an industry many have failed in?

Sorry to go off-topic but since the question was about oscilloscopes I felt I had to add a logic probe!

Re:Bankruptcy Auctions!

[AndroidCat]

At least the equipment ended up at auction. Hope none of the biotech "development" ended up in the dumpster out back. Dawn of the Drosophila Melanogaster!

Tax purposes...

[teledyne]

This is a little bit OT, but you can write off any purchases required for work, this includes education. Perhaps writing off that expensive oscilloscope would be equivalent to not writing off a less featured model.

Re:Here's one to check out -Price page is unreacha

[msgmonkey]

Price page is here but it looks like it's around $900.

Re:Here's a good one

[rco3]

Err... I came up with a 5-figure, used, standalone HP.
Was that supposed to be funny?

Try the sound inputs for a demo

[Anonymous Coward]

For cheap demo purposes, consider using the analog sound ports (line-in). I have had good success doing that for lower speed (44.1K).

I was looking for a PC based scope but couldn't find quite what I wanted.. I recently bought a used Tektronix 2215 for $50.

Re:Try the sound inputs for a demo

[Rosco P. Coltrane]

For cheap demo purposes, consider using the analog sound ports (line-in). I have had good success doing that for lower speed (44.1K).

That's not going to help you display DC and very low frequency signals. In fact, a soundcard's frequency response is un-linear enough that you really don't want to use one for demo purposes.

Like Skee Lo, I wish...

[ObviousGuy]

I sometimes think back to my college days and really regret that I didn't focus more on the hardware side of computer engineering, primarily delving into the Computer Science land of algorithms and language design. In the last several years of my employment in the embedded space, I have come into contact with more hardware than you could shake a stick at, and without that grounding in hardware that I should have gotten in school I feel a little overwhelmed when faced with anything deeper than a block diagram.

I also wish that teachers like yourself didn't have to worry about providing materials like this within such a tight budget. It doesn't sound like this is just for this year's class, but something that can be used year after year. $300 for a material that can be used multiple times seems very cheap, especially considering the intrinsic value of the tool. Schools should be at liberty to spend what is necessary to bring the classes up to exceptional levels. Considering how the U.S. lags behind most other modern Western nations in Math and Science, such tight-fisting seems to be one significant factor in this drop off.

Good luck in finding the right tool.

Educational device

[Rosco P. Coltrane]

Two thoughts about your question:

- Do you really need 40MHz for educational purposes? Unless this is a device to be used in a college or higher education class , you can display sub-10KHz signals to teach a class how to use a scope.

- When I was at school, I learned how to use a real scope, with knobs and buttons and a not-so-perfect green screen, and I reckon it was way better to touch these dials and controls and have a direct feel for what they did on the screen than set some virtual thing and grab perfect-looking samples, to understand how things actually worked.

In short, any old regular scope that's well explained by the teacher is probably better than any interface+software setup that "isolate" the student from whatever electrical phenomenon he's trying to expose.

Re:Educational device

[Rosco P. Coltrane]

On the one hand, it's cool when kids get to learn with the best equipment.

I'm afraid this is one of the greatest misconception in the world education. It's definitely not cool when kids get to learn with the best equipment : kids should learn the basics on simple, self-explanatory equipment. Complication and better equipment can come later, when the basics are understood.

That's the same reason why, after universities have taught CS students Java, C++ and Visual Basic before C and assembler, and churned out unfinished computer "engineers" for years, us low-level programmers still get high-paying jobs doing the old non-object-oriented, boring un-cool engineering the right way.

Re:Educational device

[Enuteez]

Do you really need 40MHz for educational purposes? Unless this is a device to be used in a college or higher education class , you can display sub-10KHz signals to teach a class how to use a scope.

They might need the higher bandwidth - seeing what the kids these days are doing in every aspect of technology, blows away anything I ever came close to. A good tech teacher won't stick to old curriculum, but try to expand the class as close to the leading edge as they can.

As far as getting a scope, I too suggest the "real thing". I bought a 20 Mhz scope at a local utility auction last year, great shape, $100.

Re:Educational device

[Rolo Tomasi]

Scope bandwidth - you can never have enough. If your budget is limited, you're better off with a good old analog scope. Digital bandwidth is too expensive. Calculate 10 samples per Hz of the signal that you're sampling. So, if you're looking at a 40 MHz sinewave, you need 400 MSPS. And that's just to roughly make out the shape of the waveform, 800 MSPS would be better. Just imagine what a single period of a sinewave looks like when it's divided into only 10 discrete levels. Looks like a staircase.

The other thing to consider is the input amplifier bandwidth (this applies both to analog and digital scopes). This is also known as slew rate. It describes how fast the input amp can follow a signal change. Imagine an ideal square wave with zero rise time. It has infinite bandwidth. What does this mean? If the signal has a faster riset time than your input amp, your edges will be smoothed out. If I look at the output of a 40 MHz TTL oscillator (which outputs a squarewave) with my 60 MHz scope, I see what is almost a sinewave. "60 MHz scope" means the scope can display a 60 MHz sinewave. The sinewave is the waveform with the slowest slew rate. All other 60 MHz waveforms will also look like a sinewave on this scope. If you want to analyze square waves, your scope will only show a halfway accurate depiction of the signal if it has upwards of ten times the bandwidth of the signal.

There are also problems when measuring high bandwidth signals. Above about 80 MHz, you need to use BNC jacks on both sides, properly terminated with 50 Ohms, or the stuff you see on your scope screen will have very little to do with the actual signal. Not many outputs can drive 50 Ohms. You need to build special prototypes of your stuff that are intended for scope measurements. You can't just take a scope to your CPU or stuff like that.

If I had to make a recommendation, get a 60-100 MHz analog scope in good condition. Tek 465 is a good model.

If you want to look at digital stuff, get a logic analyzer. There are some interesting DIY projects on the web.

For higher frequency or RF stuff, a spectrum analyser can't be beat. But good ones cost more than a luxury car. If you're really serious, there are DIY projects on the net for that, too.

Re:Educational device

[I don't want to spen]

Very off-topic, but I remember seeing a demonstration 10-15 years ago of the latest Spectrum Analyser, where the salesman made a big deal of the battery backed RAM saving the settings when the device was switched off. One of the older engineers said "we've got that on the analogue spec analysers, we call it a knob."

Re:Educational device

[Aussie]

I spit upon VB. *spit*

no no. Spit on Fosters, VB is drinkable.

Re:Educational device

[gemtech]

yep, the last 2 places that I setup a lab in, I've bought a decent digital scope AND a Tek 465 or 475. Sometimes you've got to see the REAL signal, glitches and all.

Re:Educational device

[R2.0]

For used scopes:http://sphere.bc.ca/test/

While you are at it, grab some slide rules and Nixie tubes.

Re:Educational device

[Thomas Shaddack]

...interface+software setup that "isolate" the student from whatever electrical phenomenon...

Well... there are certain high-voltage phenomenons I *prefer* to be isolated from. ;)

Re:Educational device

[cybermace5]

A 465 is good, but a 465B is better. The Tek 465 is about 30 years old now, and the 465B is only 20 years old. I was able to pick up a nice 465B with all manuals and accessories on eBay for $100 recently.

If the poster really wants a digital oscilloscope, head on over to fpga4fun.com. There's some neat little FPGA projects, based on a little FPGA board the guy designed and is now selling for $50. One of the applications is a digital sampling oscilloscope; it actually looks pretty neat. With the FPGA board and ADC board, it's pretty cheap too.

Re:Educational device

[tftp]

The parent poster is correct. The bandwidth of any signal that is not wave goes beyond its lowest spectrum spike. Nyquist equation must be applied to the highest frequency that you want to see.

Re:Educational device

[tftp]

I accidentally deleted 'sine' after previewing. The sentence should read thus:

The bandwidth of any signal that is not a sine wave goes beyond its lowest spectrum spike.

Re:Educational device

[Rolo Tomasi]

No, it's not. You don't buy digital scope to analyse perfect sinewaves. When you're looking at complex waveforms that might include single events and glitches, you need at least a sampling rate ten times your signal frequency. The only way you get your original signal back if it's been sampled at or near the Nyquist frequency is through interpolation. That might be ok for audio applications, but when you need to extract secondary information from the signal, there's just no way. Ten times is the bare minimum, and Tektronix advertise their scope bandwidth as 1/10th the sample rate.

Re:Educational device

[Fizzl]

Well, IMO, that fits to this analogy.
I too learned using oscilloscope 'the hard way'.

I think the old analog oscilloscopes are to frequency analysis as assembler is to programming.
When you use an old oscilloscope you get the feeling you know what you are looking because you have to tune it carefully and actually beforehand know something about what you are trying to look.

I learned programming first with BASIC on Commodore 64. Then with Visual basic some years later. After that some C. At this point I knew something about how computers (processors namely) work. I gave assembler a shot. I'm not very proficient with it, but I learned more about memory management, registers and other low level stuff. Nowadays learning a new programming language is not a problem. Instruction sets, stack orders, OO theory and procedural theory (to name a few) are just components of programming as a whole. Language doesn't matter.
I haven't done any project where I would necessarily need assembler to anything, but it eases atleast debugging when you know what the processor is supposed to do when you do a loop, comparison, manage a C structure or class members.

I'm a curious person. I sometimes reverse engineer binaries just to have a glimpse at some particularly interesting phenomenon in a program. I found it very pleasing when I actually understood the output of a disassembler on the first try.

I'm also getting increasingly offtopic here, so I'll shut up now. :)

Re:Educational device

[jelle]

When people say 'a 40 Mhz scope',they mean a scope with which you can measure signals up to 40Mhz. Sure, nyquist says that you'll need only 80Mhz to sample a 40Mhz bandwith. But for measuring that isn't really what you want:

The reason why people say you need 10 samples is because if you sample at 80Mhz and view the difference between a 40 and 39 Mhz signal, then the 40Mhz signal will look like a perfect 40Mhz square block signal (*1), and the 39 Mhz signal will look like a 40Mhz square block signal, but where one in every fourty blocks takes twice as long. That is not a good representation of the clean 39Mhz signal at all and it is precisely the reason why you need more than 2 samples per period of the maximum frequency you want to measure with a digital oscilloscope.

Plus, if you sample a wideband signal at 80Mhz, then you'll either have a lot of aliasing problems around 30-40Mhz, or you will have to deal with the signal attenuation of the lowpass filters in the analog frontend.

*1: only if the 40Mhz is exactly in phase with the 80Mhz clock of the oscilloscope, which is never the case, hence even the 40Mhz signal will look bad.

Re:Here's one to check out -Price page is unreacha

[Psychotext]

Some more info:
http://www.redacom.ch/messtechnik/softdsp/s ds_more infos.htm

This site lists the price as US $930.
http://www.techonline.com/community/tech_gr oup/tan dm/news/31646

Re:Here's a good one

[Anonymous Coward]

This is not an informative comment - the budget is between $300-$400, and the oscilloscope linked is $21,500 list price - I doubt the used price would be within the budget. Mods, let me remind you that moderation is not a race. Follow the link and pay attention before you assume it's informative. I'll gladly take the karma hit for this if the mods resposnible for this can wake up.

3 times the highest frequency being measured

[Futurepower(R)]

Remember that the oscilloscope bandwidth close to the frequency of the waveform being measured distorts that waveform. (In phase if the frequency being measured is a sine wave.) You need an oscilloscope bandwidth maybe 3 times the highest frequency being measured.

ICs often have very high potential bandwidths, and, when something goes wrong, even an audio IC can have sometimes have parasitic oscillations at extremely high frequencies. If you are working on a circuit, you need to be able to see those parasitic signals.

I don't like this fact, because it is expensive, but 100 MHz seems to be a good oscilloscope bandwidth. I bought a very old Tektronix scope to get the needed bandwidth at a reasonable price.

Re:3 times the highest frequency being measured

[Anonymous Coward]

it's *5* times the signal.

see the tektronix documentation, for ex. 2x is the standard shannon-nyquist theory, but to get proper results, go 5x. tek has a huge document on it, quite informative.

Re:3 times the highest frequency being measured

[Walt Dismal]

The previous poster's logic is flawed. Just because an IC is USED in an audio circuit does not mean the bandwidth of the IC is LIMITED to audio. Case in point, many high gain high bandwidth op amps can and do oscillate at frequencies well above audio if the physical circuit layout supports it. Having an idea of what frequency things are happening at is useful in analyzing what the problem is. And even being able to see the waveshape can give a clue to what is happening. But if it's an RF oscillation, you need good bandwidth on the scope to see details.

Re:3 times the highest frequency being measured

[Anonymous Coward]

I think it's at least 10 times the signal.

Imagine a sine wave.
If you do 2 samples/period, you measure at 0 and 180 degrees and you get a flat line.
If you do 4 samples/period, you measure at 0, 90, 270 and 360 - resulting in triangular waves.
If you do 6 samples/period, you measure at 0, 60, 120, 180, 240, 300, 360 - the result is more like a sine wave, still the amplitude is about 30% off.
If you do 10 samples/period, the result finally resembles the original (to a certain degree).

Who the fuck modded this Informative?

This is flat out wrong.

The sampling theorem is, strictly:
If a continuous function only contains frequencies within a bandwidth B, it is completely determined by its value at a series of points spaced less than 1/(2B) seconds apart.

This means that with anything greater than 2 samples you can theoretically reconstruct the continuous bandwidth limited signal. So, your first example is somewhat right, and is why we say "less than 1/(2B)" rather than "less than or equal to" This means 2.1 samples/period or even 2.00001 samples/period is enough.

You are making a common misconception that the reconstruction of sampled signals is done by plotting points and connecting the dots with a line. This is not the ideal way. Ideal reconstruction looks something like this:
Sigma(i=0, K, x_i*sinc(pi*(t-t_i)/dt)). Of course this is not a practical reconstruction in real time applications because of the need for "future" data, but with it you can mathematically prove to yourself that one can reconstruct perfectly with any sampling rate greater than twice the maximum frequency.

You should read up on signal processing.

The OP was talking about bandwidths as it applies to practical devices which involves stuff having to do with clock jitter and SNR (oversampling can be used to increase effective SNR).

Re:3 times the highest frequency being measured

[sbaker]

THe frequency rating of something like a scope refers to the highest frequency sinewave it can reconstruct. Nyquists sampling theorem says that you need MORE than twice the frequency. If you have exactly two samples for one cycle of a sinewave, you can't reconstruct it. However, if you have 2.1 samples - you can.

You are concerned about reconstructing the details of the shape of the waveform - but that's not at issue here. We're only promising that if you look at a fourier transform of your signal - then the highest component of that that we'll reconstruct must be less than half of our sampling frequency.

When we are way up there where we have only two-and-a-bit samples, the only shape we can possibly see is a sine wave because anything else would have higher frequency components - and then we are off the hook - we don't have to reproduce those kinds of waves accurately.

So - the issue is whether you can deduce the phase, amplitude and frequency of a sine wave from just two-and-a-bit samples. Nyquist says you can - and he's right.

Stop thinking about how you'd draw graphics of a sinewave using only three numbers - this is signal processing - not graph plotting.

If you want to see a 40MHz square wave, you may well need a 400MHz scope - but for a 40MHz sine wave, a 40MHz scope (which samples at a little over 80Msamples/sec) should be plenty.

Re:3 times the highest frequency being measured

[calidoscope]

The sampling theorem is, strictly:
If a continuous function only contains frequencies within a bandwidth B, it is completely determined by its value at a series of points spaced less than 1/(2B) seconds apart.

The key assumption is that the frequencies contained by a signal are indeed limited to a bandwidth B. For example, an NMR Free Induction Decay signal may have a linewidth of 1 kHz, but if you try to use a 1 kHz filter on the signal, it is going to look very distorted (even with a gaussian or bessel filter). The key issue here is that while the decay may have a bandwidth of 1 kHz, the initial rise may have a 50 kHz bandwidth.

Basically any time you want to maintain reasonable time domain response, you need to use either a gaussian or bessel filter. Neither of these filters has a particularly rapid roll-off and it ends up that a sample rate of 10X of the bandwidth is useful to minimize aliasing.

Comment removed

[account_deleted]

Comment removed based on user account deletion

Not PC

[linuxwrangler]

OK, I know you asked about PC based scopes but if a plain old scope will do the job consider used.

A friend of mine bought a couple at a ham radio swap meet from a guy who buys surplus lots. IIRC they were dual-trace and something like 20MHz (he ended up getting one for me and for several other interested friends).

They were selling for ~$20 which means you could have a scope for every student in a class of 20 and still stay in your budget.

Re:Not PC

[drinkypoo]

I was thinking that one advantage of a PC scope is that you could project it. It would be neat to project that, and then next to it project an enlarged view of what you're doing, say probing a PC board. I don't know if this person is doing this or not but it's certainly one option to consider. Projectors are getting cheaper all the time, they're pretty readily available now.

Must it be PC-based?

[Hayzeus]

You can generally get excellent deals on analog, non-pc based scopes on eBay. I use a Tektronix 2235 100mz dual trace unit that only ran me around USD $200 -- and this was a few years ago.

I also have an Ozi-Fox handheld that has a PC and/or palm-based interface. It only does 20mhz and is single trace, but they are fairly inexpensive (< $90.00 USD) -- you could buy multiple units for classroom use. The display on the unit itself is not great, but works well for quick-and-dirty work.

Good luck -- m

How bad are "soundcard" o-scopes?

[NotQuiteReal]

I haven't messed with it in a while, so I don't even know if there is software out there for modern OS's. But back in the day, if you are willing to use a real pc as your input device, and get a "good" sound card; with a high SN ratio and some software to be a "cheap scope".

After all, a DSO is "just" a D/A, and the input of sound cards is the same.

Maybe the sample rate on sound cards is not high enough, but the specs on some of the latest SoundBlaster (creative labs) cards are impressive (106dB...).

If you really need a good scope, you'll likely have to spend money. But if you are a hobbiest who just needs to see basic waveforms, maybe there is some good, cheap software out there that takes advantage of commodity soundcard hardware?

Re:How bad are "soundcard" o-scopes?

[madcow_ucsb]

106dB isn't a sample rate, that's gain...

I think the real issue with using a soundcard *is* the sampling frequency (44kHz? 96kHz maybe?) and you'll probably let out the magic smoke if you plug more than a few volts into it so you need some sort of voltage divider there for many signals. Plus I don't know how much filtering is done on the line-in side.

That said I'd say it may be more cost effective to get some used stuff. I spent about $100 on ebay for an old Tek 465. 100MHz, good condition. And I can jam the probes into a wall socket with no worries. Good enough for most of my purposes. In college we had nice digital storage scopes (and at work we've got the fancy color ones) so now I've been spoiled. But I think if you're gonna teach kids how to use a scope it's best to use the real thing. I like the nice clicky knobs on the old Teks.

Re:How bad are "soundcard" o-scopes?

[genixia]

One thing that everyone overlooks with a soundcard 'scope'. It's AC coupled only - there is no way to measure DC offsets.
The other thing that should be mentioned is the fact that the line input doesn't exactly qualify as calibrated. Whilst this doesn't always matter too much, it is still a limitation. You'd need a good known signal level (AC signal, obviously) to provide any form of (non-NIST-traceable) calibration.

Also, don't forget that the input range is very limited. In order to provide a useful voltage range you'd need to build an instrumentation amplifier. This entails time, money and effort. By the time you've added a couple of useable probes, you've spent over $100 for a 2 channel 22KHz bandwidth non-calibrated AC-coupled only scope.And we haven't even discussed software :o

Personally, I think that trawling ebay is a much better proposition. I know from experience, having built a soundcard scope previously. After a few months trawling ebay I hit the jackpot and won a poorly described auction resulting in a Tek TDS360 for about $150. It also came with a Tek PS280 power supply and a BK Precision 4040A. Yep, about $3200 from reputable dealers...

Granted, that was a case of extreme luck, but if you're patient and you brush up on your ebay searchfu you should still do way better than a soundcard scope.

There are some reasonable PC-based scopes, (eg the Bitscope mentioned in the submitted article), but second hand Tektronix scopes from ebay are still better value IMO.

Re:Here's a good one

[Grishnakh]

They've got to be kidding. $21,500 for a machine that runs on Windows? Why would I want an oscilloscope that blue-screens?

Why PC tethered?

[Jeff DeMaagd]

It seems people on slashdot are a bit overeager to buy PC based devices that can't be used as a standalone device. So far that I've seen, the benefits are mostly just cost, at the expense of portability, usability and quality.

I'd just find a real scope on surplus somewhere.

I just have a 'scope on "loan" from a local EE guy. Just an analog one. Effectively it is mostly a gift, but there are times he wants an analog scope so he wanted the understanding that he can get it back on occasion. For most uses, a digital one does fine.

Re:Why PC tethered?

[ChrisMaple]

A good PC-based device allows storing the waveform. This makes documentation much easier. Scope cameras are a nuisance and using them a lot runs into significant film costs. Standalone digital oscilloscopes with storage capabilities are less convenient and not cheap.

Did you look all that hard?

[Jerk City Troll]

It is not difficult to find a veritable mount of cheap oscilloscopes on eBay. You say you only need it for demonstration purposes, so why do you need something shiny and new? It can even be argued that the older analog oscilloscopes are better than newer digital ones. As always, resort to eBay if you need something not so good, and fairly cheap. Chances are you can find it there.

Found their price list

[Professor_Quail]

I found their price list page through the google cache...seems like their stuff is out of his price range, but here's the link anyhow:
SoftDSP Price List

Audio Frequency Freebie

[G4from128k]

If a 2 channel audio frequency scope is all you need, then Oscilloscope 2.5 for Windows might do the trick. It uses the inputs on a standard sound card to grab 2 channels at up to 20 kHz. Disclaimer: I've not used it and a bit of Googling may find better alternatives.

Its slow, but is free (assuming you have the sound card).

Re:Audio Frequency Freebie

[unfies]

You've got limited voltages when using a sound card based solution. Free is good, but it's usability is near nil. Not to mention that a sound card's dsp may muddle the input.

RS232 is 9-11 volt in of itself...

Also, if they're doing PIC or 8051 work, having at least a MHz or 10MHz scope is handy to follow any of the bus / etc lines.

Windoze luzers with Tektronix 2400-series DSOs....

[John Miles]

... can download free/open-source plotter emulation software at http://www.qsl.net/ke5fx/misc/7470.zip. This may be helpful to you if you buy an older scope from eBay. It will let you grab screenshots, overlay them, print them, and save them in several formats including their original HP/GL-2 plotter language. You can see some typical screen captures at http://www.qsl.net/ke5fx/synth.html.

I use a Tek 2430A on my own bench. These are great scopes -- you can get 150 MHz bandwidth for about $400-$600. A National Instruments GPIB adapter to interface it to the PC will set you back another $100.

I'm trying to add support for as many instruments as I can to this package. Any interested parties should feel free to email me...

Try the USRP

[gustaffo]

If my understand is correct, some of the guys from the GNU Radio Project have developed a USB based software radio device that works with in linux. It is called the Universal Software Radio Peripheral. I think the first prototypes have shipped. The cost is pretty close to your price range. You can see it in action running an oscope program here. And of course it can be extended to do many more exciting things.

Re:Try the USRP

[dfranks]

Except that afaik it will not provide any triggering capability (other than software pseudo-trigger). This may be partially offset by the ability to record really long sample sequences.

Bitscope

[GigsVT]

Since no one who's replied has answered your question, instead choosing to talk about unrelated things, I have to say that I'd go with the Bitscope.

Visit #electronics (our electronics+open source channel) on irc.freenode.net if you want to discuss.

Re:Here's a good one

[John Miles]

Quite a few scopes by both Tektronix and Agilent run Windows these days. Windows can be a reasonable embedded platform. It provides a consistent user interface, saving the equipment manufacturer a lot of software work that's outside their core competency. System stability isn't too bad since the OEM maintains tight control over the drivers and only run one application.

Not a bad solution, all in all, at least until you hook up an Ethernet cable to transfer some plots and your $20,000 scope gets r00tz0red and drafted into service in the war against SCO.com.

nyquist frequency

[jonniesmokes]

Missionary Man asks: "I'm an electronics teacher... ...Ideally I'd like something with a bandwidth of up to 40MHz and 2 channels.

The bitscope only has a 40MS/s data aquisition rate. Assuming that that's for both channels - 20MS/s each, then your left with a nyquist of 10Mhz. And you really need to oversample a waveform a lot more than x2 to see what it looks like. The analog bandwidth of the bitscope is high, but the A/D conversion will result in a lot of aliasing. That said. Its a really impressive unit for $400.00. I didn't think you could find something nearly that fast for under $700. Not exactly what you're looking for.

The software for a scope is pretty important - but without the raw A/D speed and resolution you won't get very far.

ATTENTION MR. SENSE OF HUMOR

[Jerk City Troll]

Yes, that was supposed to be a joke. That is probably one of the highest-end oscilloscope anywhere in the world.

It's funny. Laugh.

Re:Educator?

[NoseBag]

Ya left one out. Write/go to any local company doing e-tech type manufacturing or engineering. Ask if they'll donate their old obsolete eqpt that they've already written off. I've never been in an engineering lab yet that didn't have at least one dinosaur in it.

Re:Here's a good one

[cscx]

Don't make me tell you about the time a lab full of $70k Tek logic analyzers for a class I took had to be shut down because the douchenozzle sysadmins put the LAs on the Internet with external IPs (no firewall even), yet never thought of patching them. They all got infected with one of the worms.

Re:MHz vs. MSPS

[GigsVT]

You don't need 10x samples for most things. You need around 5x to catch most transient events. You only need 2x to make a waveform per Nyquist.

Most digital scopes do a sort of interpolation when the frequency is above Nyquist, they will sample the signal for several periods and reconstruct what the waveform looks like, this works with any repeating signal, but when you use this you can't catch transient events, for that you do need a sampling rate several times the base frequency.

Try DRMO for some HPIB/GPIB compatible gear

[pvera]

DRMO = Defense Reutilization Marketing Office

This is the military agency that sells surplus equipment to the public. They usually have stuff like what you need.

If you can find something that has a HPIB/GPIB bus connector (IEEE-488) then you can connect it to a PC and use program your own interface (the libraries are very simple and very well documented). We did this both in the Army and also at a commercial satellite communications company (ours was to interface with HP spectrum analyzers thru IEEE-488).

Re:Try DRMO for some HPIB/GPIB compatible gear

[cnvogel]

...and the old PCIIa GPIB-interface cards for the PC (they have a 8bit ISA bus!) are supported by linux-gpib since not long ago!

http://linux-gpib.sourceforge.net/

They are no longer supported by national instruments since windows 3.11/DOS, so you can get them very cheap (or for free) and they work very well under linux!

2340A ...

[__aadkms7016]

Happy memories of my 2340A, but I dunno if I
would recommend spending cash to buy one on
the used market ... they ran so hot, and their
mean-time-to-failure reflected it. We had a few
dozen under our control (research lab + class lab),
and there would always be a few with little yellow
Post-Its on them waiting to be sent out for repair.

SoftDSP Digital Oscilliscope

[francisew]

softdsp.com
I bought one two years ago (around 800$ canadian)
it's pretty good, does 200 MHz / (5 GigaSamplesPerSecond equiv., whatever that means), two channel, USB.
The software isn't great. I don't think there is a linux port... I'm lazy, haven't checked recently.
The actual device is really sweet. If I haven't blown it up in two years, it is pretty solid! (I'm a chemist, and I do things like attach 400V power supplies to it randomly, I'll feel bad if it dies. Or me.)
Good luck!

Re:Here's a good one

[iminplaya]

Quite a few scopes by both Tektronix and Agilent run Windows these days.

Yeah, and they take just about as long to boot up. It's ridiculous. Anything longer than 2 seconds is unacceptable. I can imagine that a bic lighter will soon be computerized and will require a 30 second boot up just to light a joint...err...cigarette...yeah, that's it.

Re:Cheap PC Oscilloscopes

[unitron]

...type "Cheap PC Oscilloscopes" into the search box and click "Search".

If you google for "Cheap PC Oscilloscopes" with the quote marks included all you get is a link to this article.

Labview

[Anonymous Coward]

If you really want to give your students a head start, I'd suggest finding any cheap scope with a GPIB interface and get an educational copy of the LabView software

http://www.ni.com/academic/edu_dsct.htm

(you should double check that the educational version actually supports GPIB because I don't recall if it does).

There's a hell of a lot of corporations out there that use LabView for all their test equipment, so there's a good chance your students will run into it when they get jobs.

PCI based oscope

[Triode]

Many people make them, and they are real oscopes on
a PCI card... but the ones I have used were GaGe...

http://www.gage-applied.com/

Should not be too pricey, and I think they have
educational discounts. They are the best option
I have seen to get a real oscope in a computer, and
the sampling rate and digitization will beat a sound card hands down.

Take a trip down to your local electronics swap...

[Ho Kooshy Fly]

Personally you have to be careful about many of the "PC" based scopes that are out there. They usually suffer from bad analog bandwidth and short memory depth. Also you have to pay particular attention to many of the voltage/impendance limits of "PC" scopes.

Personally taking a trip down to your local electronics swap meet is not a bad idea if you have one nearby. Hear in SiValley there are a few around on the weekends where you get some older Tek/HP *cough* Agilent scopes for pennies on the dollar. Sometimes they need some work but most people are honest about it.

-Ho

Re:MHz vs. MSPS

[Anonymous Coward]

Nyquist is about waveforms. If you don't understand the relation between waveforms and frequencies, then you and I are just going to have to drop this conversation right now.

You need 2x samples to capture a waveform. Mathematically. However, we are in the real world, and 5x is considered generally adequate. Truthfully, most engineers won't let a 40MHz scope anywhere near a 40MHz signal; equipment doesn't tend to perform optimally at its edges.

As to why buy a digiscope for repeating signals: data capture is nice. Especially when you can capture raw sample values and spit them into MATLAB to do some serious data analysis. Also, there's the fact that you can't buy new analog scopes anymore. Finally: most DSOs will also function as a spectrum analyzer. Which is great on your repeating signals.

Radio Shack (don't laugh)

[Sam Nitzberg]

I remember some years back that radio shack had a serial (DB-9 interface) probe with oscilloscope PC software - for about $100.

I don't think that this would have the range that you wanted, but I am sure that this would have it's place.

By the way, did anyone here have one ?

http://www.iamsam.com

Used Scopes

[photonX]

I don't know if you are considering used or not, but if you are...

SurplusShed is a site where I've bought optics from time to time, but they carry some electronics also.

To quote the website:

http://www.surplusshed.com/pages/item/r1456.html

This is a powerful 100 Mhz oscilloscope with 5 channels and 12 traces. It has a four way trigger off either channels 1, 2, 3, or ALT. Trigger lock for stable automatic triggering for complex signals such as video waveforms. Can display several Lissajous patterns at the same time. 5 mV to 5 V per division (1 mV with magnifier) and 2% accuracy. Sweep speeds are 20 ns to 500 ms. This is the scope that is being used in production, testing, R&D, and home shops because of its versatility and portability. Tested and in good working condition. Complete manual copy included. Only have a few."

Oops, forgot to grab the price, but it is around US $225

Reaktor

[plams]

Native Instrument's Reaktor may be a musicians tool, but it includes most of the building blocks for making oscillatory tools, too. It's like LEGO, but for making DSP thingies. Since most soundcards record at least 44.1 khz (and you need 40khz) it may be a solution. Of course, if you're trying to analyze signals stronger than signals within "line signal" range (+/- a few volts) your soundcard may not be appropiate - though you should be able to normalize the signal with some rudimentary electronics :-). Also, if you need a log of the recorded signal, Reaktor can't help you. Otherwise, it probably shouldn't take long to write an ALSA application for your needs.

That's what a hacker do - take some existing tech and use it in new ways. If you can live within the frequency range of sound (up to 96khz, for most cards) a sound card is an excellent tool for signal analysis. Plus: there's already many tools and libraries out there for audio manipulation - Heck! you could probably even write the software for you needs in Python!

One to Avoid

[certsoft]

I bought a PC Multiscope from Jameco and found out that it didn't actually sample both channels simultaneously, making it basically worthless. One of the things you want to be able to do is to look at clock and data lines and measure the timing between them, and for that you need simultaneous sampling. Needless to say, that pile went back to Jameco.

I bought a DSO-2100 from Link Instruments and have been very pleased with it. Probably one of the best investments I've ever made.

Re:Here's a good one

[afidel]

New they are at least 4x that, and yes it is crazy to put a windows 9x device which you can't patch on the network. What we did is put ours on a vlan with the only other device being our SAN device. Then the data dumps were pulled off the SAN device for analysis on either the lab network or engineers desktop workstations.

Re:Here's a good one

[iminplaya]

Let me re-word that...At least it doesn't need this to run.

Optascope

[GarthSweet]

I have an Optascope 81M USB scope from
http://www.optascope.com
I recommend it highly. Nice software and really works well for me. Also only $189.00!

Specs are:
1 Ms/S Maximum Sample Rate (500Ks/s 2 channels)
200 KHz Bandwidth
20Vpp Max Input for CH1 & CH2
8 Bit Vertical Resolution
2 Channel
External Trigger Source
Trigger on Rising or Falling Edge at Any Voltage
Variable Trigger Voltage on DSO channels
10%, 50% and 90% Horizontal Trigger Position
Auto or Normal trigger modes
USB interface

Re:Optascope

[dgmckay]

TIP: If you buy these through Parallax there's a volume discount that cuts the price down to about $170.

Dupe!

[bishr]

This was covered a few years ago; no surprise that most people forgot. The answers are mostly the same; still a good read though: http://ask.slashdot.org/article.pl?sid=01/12/07/19 1220&mode=thread
-----
Trogdor the Burninator!

Cheap, but not PC, scope: Tektronix 1002

[pingswept]

You can get a new Tektronix 1002 (two channels, 60 MHz) scope for $995 without any educational discount. If I were in the market for a scope, I'd try to find one of those used. They're small, reliable, and inexpensive for their abilities. $400 is a probably low, but I wouldn't be too surprised to find one for $600. To me, learning to use the controls on a standard scope is worth quite a bit. (An extra $200? You be the judge.)

Re:Educator?

[afidel]

Good point. I know my last client was a wireless equipment manufacturer and when they went from 900MHz for 802.11 to 2.4 Ghz for 802.11b their old equipment was worthless because it mostly topped out at 1GHz. The old equipment was sold off to employees but they probably would have been just as happy to give it to an educational institution if they had been asked.

Why not a real oscilloscope?

[Wansu]

There are a quite a few used Tektronix 465 scopes going for about $200. Check newsgroups, eBay and go to some Hamfests.

cheap 40 MHz scope

[RadioDude]

The most common source for these type of PC-card "instruments" is National Instruments.

If you are teaching about electronics, you would be better off buying a used Tek 475 (or similar) analog scope, you can get a very good one for $300-400. They can learn about the actual circutry, timing, measurement error, etc. without
getting heavily into sampling theory and digitial
signal processing.

If you want the students to learn "the new way" of
electronic instruments, check with National Instruments about used/traded in cards, and software; they may have an educational discount.

There are also some "poor man's" type of scopes made of surplus parts, old TV's, etc.. that you can find in the back pages of Nuts& volts magazine; I don't recommend these if you want the students to learn what they will use in the future, in real-world engineering applications.

Finally, there are mixed-mode instruments that are analog with analog storage, analog with digital storage, analog with digital readouts added, various standard instruments with serial or GPIB interfaces, and s/w from the mfr or 3d party for
control and analysis.

See if you can find on some engineer's shelf a catalog/book from Tek or HP, say, from the 1980s
or 90's, this is about the vintage that will work and be in your price range.

Have you considered eBay?

[John Jorsett]

If you were considering PC-based scopes just to get the cost down, perhaps you might consider an actual used oscilloscope. There are many used ones for sale on eBay, and there appear to be some that would more than fit your criteria. For example, this one.

Check out National Instruments

[Spikeorama]

Check out the PCI/PXI/AT/USB/PCMCIA-5102 from National Instruments. I think they're about $1200 or so and 20 MHz 2-channel 8-bit, a little more than you wanted to pay but it's good stuff.

Re:Here's a good one

[Endive4Ever]

Back in the day, with even the highest quality most expensive analog scopes, you didn't trust any measurements off them before at least a twenty minute warmup.

Boy, have things gotten twitchy in tech these days, if a 30 second startup isn't fast enough. Nintendo has spoiled a whole generation.

Everything oscillates. Okay, a small exaggeration.

[Futurepower(R)]

Modern circuits are not so well controlled as someone might guess. To have 20 kHz output with little phase distortion, it is necessary to pass more than 200 kHz.

But that's not the issue. ICs allow the design of circuits with bandwidths that are literally physically impossible with discrete components. The fundamental bandwidth limitations of the transistors used in the IC may be 200 MHz or more, or even 1.5 gigahertz. Any small problem can cause a circuit to oscillate at 50 MHz, even if the IC is supposedly limited to far less than this.

All you need for oscillation is gain and some positive feedback. In the real world, circuits try all possible combinations almost instantaneously, and begin oscillating for reasons the designer never foresaw. For example, maybe there is capacitive coupling through the IC packaging, and the output circuit alone is oscillating.

This is only a slight exaggeration: There are 4 steps toward making a new electronic device: 1) Build the circuit. 2) Supply power for the first time. 3) Apply an oscilloscope probe and begin discovering all the reasons the circuit is oscillating when it shouldn't. 4) Then discover all the other reasons the circuit isn't working correctly, if any.

I was never a person who thought that killing people and destroying their property was a good way to resolve social problems, but at one time it was my job to repair the automatic flight control systems of fighter-interceptors in the U.S. Air Force's Air Defense Command.

These aircraft required 250 hours of maintenance per hour of flight. (Aircraft meant to be sold to other nations, also, required 15 hours of maintenance per hour of flight. I've followed the development of weapons systems ever since, and my opinion of what is actually delivered is that it is often fraud, or close to fraud. United States taxpayers: Your assigned duty is to find the money to pay, and to avoid thinking.)

Anyhow, during training flights it was required to pull several g's. Sometimes at high accelerations the electronics would go completely crazy, and all inertial reference would be lost. The only fix for this at the time was to land, regain stability, and take off again. The aircraft that had this problem were therefore not much use for any situation actually requiring defense. Worse, the problem seemed to have nothing to do with any particular aircraft, but seemed random.

One day while trying to make a faulty system work on my bench test mockup, I discovered the reason. Some of the amplifiers that controlled the gyros had high frequency parasitic oscillations at perhaps 100 times the normal frequency of operation. You couldn't see the oscillations with normal equipment because the frequency was too high. I had borrowed an oscilloscope from some co-workers who worked on faster electronics.

The design of the amplifiers was acceptable, but many of the amplifiers had bad solder joints. Those with bad solder joints would oscillate; oscillating amplifiers would amplify at the required low frequency, but had a much smaller dynamic range than amplifiers that were not oscillating. (Yes, that bad solder joints could cause this doesn't make much logical sense, but most parasitic oscillations don't make much logical sense.)

The amplifiers had other defects that caused them to have a high failure rate. Every time an amplifier was pulled from an aircraft for a conventional repair, an amplifier was drawn from stock and put in the waiting aircraft so that the aircraft would be immediately operational. That was the reason the instability problems kept moving from aircraft to aircraft.

I drew a circuit diagram of my test setup, wrote an article about the problem, had a photographer take photos of the test setup, took screen photos of the parasitic oscillations, and sent everything to those who review such things. This had several effects. Someone at Air Defense Command headquarters wrote a letter praising my work. When everyone was reviewed for p

My 1960's scope takes about 30 seconds

[lhaeh]

You kids and your fancy new transistorized scopes'

My 1968 Tek 453 took ~two hours to warm up, and when a tube died we had to walk twenty miles in the snow just to get a new one!

AC coupling isn't a problem

[rsw]

So modulate in hardware and demod to baseband in software.

With a simple analog multipler (for example, the Analog Devices AD834) and e.g. a 5 KHz oscillator, you can AM a band-limited (say, DC-500 Hz) signal, put it in your sound card, then do the demod in software (another multiplication will work).

This will cost you, in total, about $5 (you can get free samples of the AD834 and you'll need some resistors, some caps, a couple op-amps, and some wire) and will give you DC-500Hz through your modulator or 20Hz-24KHz without it. Not too shabby, especially compared with $500.

By the way, if you're going to spend $500ish anyway, why not pick up a Tektronix 2445 or 2465 on EBay? The 2465 has 350MHz bandwidth and is, IMHO, one of the nicest all-around scopes out there.

Re:AC coupling isn't a problem

[ajohn]

"By the way, if you're going to spend $500ish anyway, why not pick up a Tektronix 2445 or 2465 on EBay? The 2465 has 350MHz bandwidth and is, IMHO, one of the nicest all-around scopes out there." This is the best idea of the lot. In real life they will use a stand alone scope 90% of the time. The instruments on eBay are dirt cheap! When the break - and they will - trash them. Any of the 2000 series from Tek will do the job. The added benefit is that you get a REAL instrument not just a simulation or another piece of software that clogs up your DOS machines.

Check out Interface's Boards

[Thurn und Taxis]

You might want to check out the boards put out by Interface, a Japanese company. Specifically, their PAZ-3161 board supports up to 40 MHz sampling rate (one channel; 20 MHz if you sample both channels). Not only does this company make excellent boards (my lab has several), they provide both Windows and Linux drivers for the boards.

I've done some preliminary work on writing signal-analyzer software for their PCI-3525 board, which I would be happy to share (it's not close to being fully-functional yet, but we've got a student who may be using these boards, so that might change soon). I'm also happy to try to adapt this code to more general use. With these boards and existing code, your task might be much easier than you originally thought. Also, their sales engineers are very willing to help solve problems. I don't know the prices on their boards (ours were donated), but they are excellent devices.

Maybe you could have your students build them?

[tech_savvy_guy]

You could have your students build a fairly good PC based O-Scope with eight 5-Mhz sample-and-hold A/D converters, a 40Mhz clock, a small bank of SRAM, and some glue logic to blast all the data back to the PC. Maybe get together with the Computer Science professors, and have their students write the PC software. Then your school would only have to shell out for the parts, and the project itself would teach your students a lot about how real-world design works. Tech

Re:Like Skee Lo, I wish...

[aastanna]

Sounds to me like the question is from a high school teacher. I seriously doubt spending any more on a scope would be worthwhile, since I'd bet it's primarily going to be used to show students wavy lines, or maybe as a glorified multimeter (he's only buying one, so it's not like the students will be using it regularly). I wish the poster gave a few examples of the types of projects his class works on.

That said, I wish schools would stop blowing their entire budgets on computer labs. I hate to see a school paying for a computer that isn't at least two years old when the money could be going to text books that aren't twenty years old and falling apart.

It would be really nice to see high school electronics courses teaching students how to properly work a scope, but you'd need enough for an entire class. It's amazing how many engineering students get 2 years into a computer/electrical engineering program and don't know how to use a scope to read important parameters from a circuit.

Another use for that old gameboy

[Ultra64]

Gameboy oscilloscope

Please... Don't go the PC route for this...

[KC7GR]

For the amount of money you're specifying, you can easily pick up a much better built and far more versatile O-scope in the form of an older Tektronix instrument.

In fact, that price range will easily get you a 475 or 475A, good to 200 or 250MHz, respectively. It will also put you well within reach of a nice Tektronix 7000 series benchtop 'scope, like a 7704 or even a 7904.

No matter what you may hear, the PC was never designed to be an O-scope, and no amount of external hardware, I believe, will ever turn it into anything that can compare, in terms of value for the $$ and quality of construction, with early Tektronix hardware.

I believe it's also EXTREMELY important to teach would-be technicians and engineers that the PC is not the be-all and end-all of test gear. Never has been, never will be. Oh, it can be useful as an instrument CONTROLLER in automated test setups, yes, but it was never intended to replace the functionality of actual made-for-purpose test equipment.

Give your students a real education. Get a real oscilloscope.

Great scope tutorial

[AgentPhunk]

here

Elab-800

[leov211]

A new pc-based scope with these functions, at US$495:
- Digital Storage Oscilloscope (DSO) 2-channels 80Msamples/sec
- Logic Analyzer (LA) 16-channels
- Arbitrary Waveform Generator (AWG)
- User Programmable Power Supply (UPPS) +/- 10V
- Programmable Clock Output (1kHz - 150MHz)

http://www.dynoninstruments.com/docs/elab-080featu res.html

How about a used Oscilloscope?

[RKBA]

How about C&H Sales in Pasadena, CA? They sell used lab equipment.