Oscilloscopes For Modern Engineers? 337
Every few years someone asks this community for advice on oscilloscopes. Reader dawning writes "I've just graduated with a degree in Computer Engineering (and did a Comp Sci one while I was at it) and I'm finding myself woefully under-equipped to do some great hardware projects. I'm in major need of a good oscilloscope. I'm willing to put down $2,000 for a decent one, but there are several options and they all seem so archaic and limited. I'm happy to use something that must be controlled through a PC if that gives me more measuring features. What would you, my esteemed Slashdot colleagues, get for yourself?"
An old Tektronix is fine for a modern engineer (Score:4, Interesting)
Get a Digital Radio (Score:3, Interesting)
Probably the best deal would be to get a digital radio. If you can live with ~150Ms/s (a tad slow, but hey), then a cheap thing to do would be to get a digital radio (SDR) system. Say Mercury SDR. Those things typically have a good, 16 bit 100+Ms/s ADC front end, feeding into an FPGA that can do a lot of processing goodies, with low noise, and you should be able to hook up a Tek 7k plugin as a front-end after a few tweaks (simply to get going). You can get everything for $700. You have open source software, full documentation, and you can put a lot of very interesting signal processing on the FPGA. Keeping sampler's speed limitations in mind, you can otherwise easily match performance of many lower-end spectrum analyzers, and $20k+ scopes.
There are no $2k digital scopes with any decent feature set to speak of, even second-hand ones.
If you're into tweaking analog, then a Tektronix 7k mainframe with proper plugins gives you everything you may need. Heck, you can even get a simple logic analyzer for those. With *analog* zoom, no less.
Re:Tek 1012B (Score:5, Interesting)
Or you can get a $370 Rigol DS1052E [dealextreme.com], and software-hack it to enable 100MHz mode. Not quite as good as a Tek, but significantly cheaper and well worth the money, especially if you're on a smaller budget. I recently got one (it's about time I bought a scope) and I've been quite happy with it for my purposes.
Info on the hack here [eevblog.com].
Get a used Analog Scope (Score:2, Interesting)
I picked up a used Tektronix 7904 for under $100. Of course, the four probes that I needed cost rather more than the scope, but that's life. The 7904 (with the modules that I have) is a 350MHz unit -- which is great for doing radio work. This setup could easily have cost $10k new.
Buy one of these online and the shipping will kill you. You need to find someone local who wants to get rid of one.
Re:dumpster diving (Score:4, Interesting)
Not really.
If they need it accurate and traceable they'd have to pay a lab to calibrate it after it was fixed. Such a lab would reject it due to it being fixed (and charge a pretty penny with no calibrated scope at the end of the process.) So they're stuck.
(This reminds me of a story my wife tells about a lab PC that had a bad case of infant mortality. The local techs wanted to fix it themselves. She pointed out it was still in warranty - so the thing to do was send it back for fix-or-replace for free, rather than void the warranty and maybe end up with a broken machine and nothing (but wasted engineer time) to show for it.
Fixing a scope adequately for home use is another matter. Then, if you ever need serious accuracy, you can do the same sort of compensation hacks that were done back in the tube days, when stuff drifted all the time and you couldn't just have a lab tune up anything complicated and expect it to stay tuned.
Not really... (Score:5, Interesting)
I have a very nice, for me, rackmount 350MHz 4 channel Tek scope with some very killer plugins.
The scopes I used at work today are really beyond anything needed for home use, unless you're into some extremely expensive hobbies.
The portable scope is a 3054B; 500MHz x4 channels. (~$10k, with options) The good one is an 11GHz x2ch Lecroy ($ almost 6 digits), I made picosecond-order measurements with it today.
The differential probe was $5k each; (wasn't that what gov. spitzer paid? lol.) our newb has killed two. (4Vmax) $2k each to fix.
If you can afford it for home use, I'd recommend the Tek 3054 or a lower bandwidth cousin. They're very easy to use.
If you can get surplus scopes coming out of downsized companies, you can get a deal; that's how I got my rackmount and a stack of plugins for $130. It was a production fixture at a missle plant in the 90s. :)
Digital is great, as long as you realize the limitations; digital displays lie sometimes. If you're going to base a paper on it, use multiple measurements with different equipment. :) I've seen fresh engineers embarrassed by artifacts.
Re:Kazkek (Score:2, Interesting)
Bullshit!
Unless the OP uses LabVIEW at work or school (and is allowed to take a copy home to play with) it's a hell of a lot more money than a decent Tek o-scope. Daq cards are fine for some things but troubleshooting isn't one of them. Stay away from used HP scopes since the damn things never triggered right even when they were new.
Re:Get a Digital Radio (Score:3, Interesting)
To get the basics going, you need a working SDR receiver -- you just buy the thing. My coworker recently got one -- the post-processor card with USB output (Cyclone II based), the sampler card with Cyclone III and 16 bit 160 MSPS LTC ADC, and a backplane and power supply. The first two were assembled.
This is quite a decent *receiver*, it has a dynamic range that's pretty much unheard of on oscilloscopes. Would make a half-decent spectrum analyzer, too. Once you add a DC-coupled front end, you may as well have an attenuator with two or three settings (say 10V/div, 1V/div, 0.1V/div), the ADC's resolution is enough to deal with it. Testing it can be done using itself -- the proof is in the pudding, I mean in the stuff you acquire.
Repurposing say a 7A13 plugin for input conditioner can be done without an oscilloscope, a DVM is all you need to get operating points right, and then you watch the signals using the device itself.
Re:My take (Score:4, Interesting)
Yeah, but the 'scope is a dedicated application with dedicated front panel controls. Windows is merely a widget provider. I've used them, and they're very nice as they support modern hardware and printouts/screenshots are a breeze. But you have to buy the ones with the full front panels - the ones that are just PCs are just... useless and you spend way too much time mousing around clicking virtual knobs. Painful.
$2k can get you a nice basic scope. That's all you need. For the rare times you need something fancy, there are many places that'll rent you the high end scopes for days or weeks. Sure you're paying a good chunk of money for someone else's loan, but unless you can ante up the $10-100K+ for those things, it's far more economical. Get what you can (surely you should be able to find a nice 500MHz scope used?) with what you have to do most of the debugging. When it comes time to debug that obscure thing, rent it.
This way you'll get a good scope for normal use, rent a oh-so-beautiful GHz level scope when you need it or even the fancy-smancy "analog digital" combined scope plus logic analyzer. Those let you analyze bus signals in standard 0's and 1's, while seeing actual signals at the same time. Plus, they can capture the analog signals with the digital, so you can trigger on some oddball logic condition on the bus and see any odd analog waveforms at the same time. But those are expensive - your best bet is renting until you can afford to buy one 10+ years from now.
And if your scope only collects dust instead of signal, you've avoided wasting a pile of money.
Scope is a thing of the past (Score:3, Interesting)
I hate to say this as a former Tektronix engineer, but you seldom need a scope, and if you do it is typically application targeted and expensive. So the general purpose scope that all self respecting EE's used to have on the lab desk is a thing of the past.
All digital work either has debuggers or with FPGAs, Chipscope Pro or other. No scope needed. And if you really need to see how the eye diagram looks with your 10GB Ethernet, the best scope may be your receiver chip. Hard to find a 40GHz scope anyway.
I actually had a Tek 2440 300MHz Digital Storage for at least a decade, but used it less and less. Became more a educational thing to show kids how AC looked. All serial interfaces are running at muli GHz speed, and RF development is more in the 5.7GHz range and higher (802.11n) Not many scope sampling at 4x or more at those frequencies.
Re:dumpster diving (Score:3, Interesting)
I completely understand what you're saying, but you list some very specific circumstances. A cal lab nominally is supposed to calibrate, not repair, so they'll simply give up when they use up the adjustment range and they're still out of spec. That's hardly rejecting "due to it being fixed" -- any number of things, including simple passage of time, can make an instrument do this. They won't try to understand why it doesn't work, just that following the cal procedure (usually with lots of in-house clarifications/improvements) the tech gets stuck at a point and that's that.
For older equipment, some cal labs offer calibration bundled with repairs, so that they'll try to fix precisely what you're talking about (when it's still fixable).
Quite often it's very obvious that someone was "working" on an instrument, and you end up undoing most of such "fixes" -- I agree there. This can potentially take many billable hours, so if they are given a go to repair, they can love such jobs.