Slashdot Mirror
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.
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
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?
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.
I have been pwned because my
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.
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?
This issue is a bit more complicated than you think.
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.
Dahlmann tightly grips the knife, which he may have no idea how to use, and steps out into the plain.
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.
[Protect Deez N-U-Teez]
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.
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.
Cloned foods give the statement "We had that last week!" a whole new meaning.
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
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.
There are 4 boxes to use in the defense of liberty: soap, ballot, jury, ammo. Use in that order. Starting now.
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.
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.
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.
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.
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.
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
The bandwidth of any signal that is not a sine wave goes beyond its lowest spectrum spike.
Gameboy oscilloscope
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)...
9/11 Eyewitnesses to Explosive WTC Demolition 1 of 2