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Oscilloscopes For Modern Engineers?
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?"
I use an R7704 at home, and a 7633 at the office.
The determined Real Programmer can write Fortran programs in any language.
As for your question, who the fuck knows?
have them take the measurements for you.
itll give you great experience in The Real World.
May I suggest you get a DAQ usb card and Labview from National Instruments. Probably some of the best investments you can do. You can do many things with a DAQ card and Labview including building your own digital Oscilloscope.
Back in graduate school, my roommate and I would dumpster dive and repair broken ones. More often than not, it's a pretty simple fix.
Like: How am I going to stop some big mean mother hubbard from tearing me a structurally superfluous new behind?
You, sir, are no engineer.
Do you even lift?
These aren't the 'roids you're looking for.
Without know what frequency range, voltage range, connectivity requirements (is computer connection USB or serial port?) I cannot help you in your selection.
OTOH you can give me the $2000 and I can give you my blessing.
What you should buy depends on what you plan to do, obviously. I've used several of the korean imports (Owon, Rigol) and although the feature set on those is incredible for the price, the units themselves have strange firmware problems that can be maddening when they strike. Also, the knockoff scopes can't seem to get "Automatic" triggering correct (they only sweep 3 or 4 times a second, no matter how fast you crank up the sweep rate, and that can be annoying when you are monitoring a signal), the Tektronix scopes are much better with regard to this feature.
I'm rather fond of the low-end Tek scopes. The LCD screen is a little slow, and there's only 2 channels, but these are not huge limitations for most basic work. I use these teaching physics and intro electronics to undergraduates - they're easy to use, lightweight, and can store data through USB or pen drives. 100 MHz for about $1200, which is OK for general use.
Building a Cheap Oscilloscope Using Your PC?
There are some interesting suggestions there.
I'm thinking that some of the more adventurous open hardware folks might think about working on a completely open hardware scope. I mean, what's better than being able to use open tools to build open projects?
coding is life
Got mine on ebay for a ridiculously low price... but like someone else mentioned, what you use it for is rather important.
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.
A successful API design takes a mixture of software design and pedagogy.
I am lucky enough to have a Scopemeter 199C. It rules. If you can possibly swing the cost, I'd highly recommend it. This model has remained Fluke's top of the line portable DSO for almost a decade, and the price has not changed for years. Portability is a great advantage for all sorts of applications, and the scope itself includes a full complement of great features including spectrum analysis, cross-channel math functions, and full DMM capabilities separate from the scope hardware. The computer interface and software is nice too. Probes and accessories are extremely expensive though, so keep that in mind.
I am a geek attorney, but not your geek attorney unless you've already retained me. This is not legal advice.
The USB scopes are maddeningly horrible at triggering, at sample rates, and at aliasing. You're much, MUCH better off going with a stand-alone scope (LeCroy, Tektronix, Agilent) than any of the ones run by PC. LeCroy doesn't seem to provide much in the way of repair schematics, but Tektronix and Agilent are pretty good in that respect. I'd spring for one of the nicer Agilent/HP or Tektronix scopes, frankly, or even a LeCroy, but never something which is limited to being run by PC solely.
This is a bit light on the requirements, but there wasn't exactly a defined need.
So generally speaking you should form some criteria.
Number of inputs, frequency spectrum, what comparative features do you need.
Next, if you are willing to purchase something used and have it tuned/repaired there can be considerable savings. Up one level from this is a direct refurbishing company that guarantees a functional and re-tuned unit.
Now, we all enjoy new and shiny toys, but the trick is being honest with yourself.If it's going to be used for hobby grade activities then don't fall into the trap of wanting the same things you might use at the office. While I would like some of the severs I actually have at work I would not spend the several thousand it would take to actually purchase one of them.
That said I would generally avoid ebay because most refurb shops will sale you the same thing on their site without the wait.
"You should always go to other people's funerals; otherwise, they won't come to yours." -- Yogi Berra
USBee has usb-based, software-driven oscilloscopes and logic analyzers to plug up with your computer. Not exactly the old, free-standing devices, but it might work for you. The price looks about right, too.
Don't skimp. Get a good one, name brand (Tek, Agilent, LeCroy, etc.) at least 100 MHz bandwidth (the higher the better), 4 channels if you can afford it, some way to get data off the scope and onto a USB drive/network. Everything else is fluff and you can pay for it if you want, but I'd say the above are non-negotiable.
Don't even think about a PC-based scope. A scope is a standalone instrument, always has been, always will be.
I used to be a certified electronics calibration technician, and I've never noticed a difference between the analog and the digital.
If $2k is your budget, and not having any idea what you're going to be using it for, I highly recommend a handheld Fluke. They were just as reliable as the old analog ones, but with more features.
This is the model I'm referring to:
Fluke 125
Official Fluke 125 page
aero2600
Please stop hurting America -- Jon Stewart
I'm an EE who does electronics design for a living, and I've done audio, SMPS, digital, FPGA, you name it. And in each case, the "best scope to use" was different:
- For analog work, or for simple microcontroller debugging, something like a USBee will work great.
- If you're doing higher speed analog, lower-frequency RF or switching power supply design, I'm a huge fan of the Tektronix DPO series. I use a TDS3032.
- For digital work (debugging serial/parallel interfaces and whatnot) I use an old 100MHz "Mega Zoom" HP logic analyzer.
- If I'm doing a design with a big FPGA, bringing lots of extra signals to the FPGA during layout time and using something like Chipscope Pro (on Xilinx FPGAs) to watch what's going on has been extremely handy. No test equipment required!
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.
Actually, there's at least company with open hardware oscilloscopes:
http://www.bitscope.net/.
coding is life
Personally I find traditional non-storage analog scopes pretty much useless for digital stuff. Really you can only use them if you can arrange for the signal in question to output a simple pattern that repeats infinitely.
Never used an analog storage scope but from what I hear they aren't exactly great for high speed stuff either.
One exception: if you can stretch your budget to get a used TDS3000 or TDS3000B series scope, that would be a good way to go.
There is one listed on ebay buy it now right now for the original posters budget of $2000
http://cgi.ebay.com/Tektronix-TDS3014-Digital-Oscilloscope-100MHz-w-HPIB-/300450756657?cmd=ViewItem&pt=BI_Oscilloscopes&hash=item45f442b831
note: i'm known as plugwash most places but i screwd up registering that here somehow in the past and now can't register
An employer. Seriously. Every piece of test equipment I've ever owned (some costing upwards of $5000 1978 dollars) was a lousy investment.
Especially when you consider that I have a lab at $WORK with scores of tools costing more than I make in a year, it's stupid to spend my own money on them.
Lacking <sarcasm> tags,
You should be able to buy a decent used Tektronix scope on ebay for $200-300, not $2000. Something in the 2200 series, or 400 series. Digital storage scope with 2 channels, A delay B horizontal, 100Mhz bandwidth.
I've been engineering for over 30 years and in my opinion there's nothing like a good old 7000 series Tektronix scope. You can pick one up on ebay and configure it with modules to do just about anything you would want a scope to do. They're old, use some power and oh by the way...they are analog. But they are great scopes. A lot will depend on what the projects you are talking about require, but as a good general purpose scope they are great. You can get all the manuals and work on the equipment yourself. And you will see electronics build the way no one builds it anymore, including Tek. I have a complete bench full of Tek and HP gear and it serves me well for projects ranging from audio designs to the latest single chip controller applications. Good luck in your search.
... at http://gtalug.org/wiki/Meetings:2005-12, Peter demonstrated the virtual oscilloscope and virtual function generator applications, which are available as open source.
The hardware unit (approx 3 x 6 x 1" thick) is available at http://www.syscompdesign.com/CGR101.html
--dave
davecb@spamcop.net
The difference between a 'scope that is a joy to use and one that is useless and frustrating is triggering. Good triggering is what gives you ease-of-use. You can't see it if the 'scope can't trigger on it. This is especially true when you are trying to catch a glitch.
In my experience, Tektronix 'scopes have always been easier to use because they triggered better than the competition. We got a bunch of money once and decided to buy new oscilloscopes. Since we worked for the government, we had to write up a tender so there could be a fair competition. It drove us nuts. The specifications for the other brands were as good as those of the Tek 'scopes. We had used the competing 'scopes and hated them. We had to bend like pretzels to get a specification that would ensure that we got the 'scopes we wanted. The specifications just don't do a good job of describing how usable an oscilloscope is. (ditto for spectrum analyzers)
The Tek 'scopes were bullet proof. I could throw my 'scope in the back of a station wagon, drive to the airport, hop on a rented plane, fly five hundred miles, hike up a mountain and the Tek 'scope would ALWAYS work when I got to the job site.
These days, with digital 'scopes, a good test is to throw a nasty waveform at the 'scope and press the autoset button. If you're looking at something useful, the 'scope is good. If you're looking at garbage, the 'scope is garbage.
These days, I have an ancient Tek (circa 1970) 'scope on my bench at home. It works great for most of my home projects. At work, I have access to 'scopes that will do 1 GHz. My buds at the NRC have a 'scope that does 6 GHz. Somehow all the 'scopes are Tektronix.
Since I started in the industry in 1974, Tektronix has made the best oscilloscopes. Some of their other stuff is crap IMHO but nobody else can touch their 'scopes. I'm teaching college now and we prefer to buy as cheap as possible. Whenever we've tried something other than Tek, we've regretted it. The Tek 'scopes have the advantage of being student proof!
For other test equipment, I would choose other manufacturers. HP/Agilent would be my choice for almost everything else that isn't an oscilloscope.
Before plunking down good $$, I'd wait and see what sort of equipment is *really* needed. Scopes are a nice tool, but there are other tools like good spectrum analyzers (with waveform analysers) and other gear that can add up quickly. I'd say, let the need present itself, then invest to the need.
---- Teach Peace. It's Cheaper Than War.
I would strongly recommend a good second hand analog one like the Tektronix 465 series which are rock solid and very cheap, and a for digital a DSO such as the Rigol (who make some of Agilent's stuff) DS1052E, this is a 50MHz 1Gs/rate and beautifully manufactured. The upside of this is that is the exact same model as the 100MHz version, so with a very trivial software hack you can turn this sub $500 DSO into a $1000 100MHz version! I would then recommend a good Digital Logic Analyser, for around $400 you can get the Intronix LA1032 (I think is the model) which is possbily the best unit on the market under $1500! View the EEVBLOG's (google it) to see the problems with DLA's and DSO's. So for under $1200 you get a 100MHz new DSO, a 100MHz S/H CRO, and a 32 Channel DLA!
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.
Truth isn't Truth - Guliani
One reason I mention these is because newer scopes, particularly the Tek 3000-series, while incredibly useful because of their size, weight, and connectivity (they have a linux-based OS that includes a webserver so you can plug one in with a cat5 and control it from your desk remotely: pure awesome!) are just about impossible to repair. Everything, *everything* is in custom silicon. On a LeCroy you can swap out the input amps if you burn one, swap out the timebase card or the A/D cards for each channel. It's like working with an old PC, as opposed to an ipod.
Also, budget for probes. Get probes rated for at least 1.5 times the scope's bandwidth: usually people ship probes that have the same bandwidth as the scope's max, but the spec on them actually means they're at something like -3dB and pretty fuzzy at that bandwidth. I got 500's for my 350mhz scope and they're beautiful. A lot of people sell broken probes and I've found, in the three I've purchased, that in every case it was a broken solderjoint where the probe cable met the board that attaches to the scope BNC. I reflowed it (no added solder for fear it'd mess with the tuning) and got three new probes for cheap.
There are people selling vintage scopes on ebay that have NIST certification, if that's important to you, but you can also get it independently certified if you need it. Newark.com has cal services, to my surprise. (They're who we use at work.)
I personally dislike Yokogawa scopes because their interface doesn't make sense to me. I can sit down at an Agilent or Tek or LeCroy and get it to do what I want pretty quickly (digital LeCroys are weird about horizontal offset) but Yokogawas I spend a lot of time reading the manual. But they're nicely engineered.
The USB scopes I've used were disappointments to me: the $ per mhz isn't competitive with a used scope, and they're typically pretty tied to the company software, which might not do what you want.
Nostalgia's not what it used to be.
If you're a C.S. person, it's likely that you are a digital person, and you will most frequently use the oscilloscope to troubleshoot digital busses. Don't skimp on the channel count, go for 4! For things like serial busses (RS-232, SPI, I2C, etc.) you will want to watch clock, tx, and rx simultaneously. For a parallel bus, you can get your clock, chip select, and a couple addy or data lines. For most problems on your board, you can get by with the scope instead of an expensive logic analyzer if the scope has enough channels. The scope is better than the logic analyzer in many ways as you can watch for issues with noise, bus contention, etc.
Every engineer has their bias, I say go for Tek! LabVIEW and DAQ are cool for repetetive measurements under automation, but there's just no substitute for a physical front panel interface with knobs and buttons when you just want to spend a couple minutes looking at a few levels.
Try to find something with Ethernet or USB. Many of the used scopes on ebay have the old 3.5" floppy, and that becomes annoying when noone in the office remembers floppy disks and you need to get a plot off the scope to send to an FAE! :)
I have one of those sitting on my bench, and I can tell you that the Agilent MSO's are awesome. You can add acquisition memory (up to 256 million points) There's nothing like being able to zoom in on 3-4 seconds of data at a decent acquisition rate to see what is going on. Look for a good used one, and then save up and upgrade the acquisition memory as you see fit later. Many scopes have a very limited amount of acquisition memory (under 1 million samples), and it really limits how much you can zoom in and analyze the data you've just taken. You'll spend lots of time wishing you had a "better picture" otherwise. Either too zoomed out to get enough detail later, or too zoomed in to have enough to see what happened. The acquisition memory is the key. 1 million data points at 100 million samples a second does not give you a very long snapshot of what happened and going down in sample rate is not always an option. Any time you have to actually make something really work where there's multiple processors communicating and bus level interfacing, and lots of stuff going on there will be that once in a day, or week, or hour that something doesnt go quite right, and the shit starts piling up, and getting late that is what you (and your fancy scope) cant afford to miss, and you sit there with an incomplete picture, go damn I wish i could zoom in, go back 100 milliseconds or a second, and see what really happened. But I guess I'll wait ANOTHER day, week, hour whatever for it to happen again, and hope I can catch it. Many times you cant set a trigger to catch this stuff reliably, and you just cant let it go if you want your stuff to work (right). Look at the MegaZoom examples on Agilent's website to see what I mean. BTW it is also second to none at displaying data, and showing you little irregularities that appear in the signal, as well as allowing you to zoom in on that portion with (quite literally) a couple flicks of the knob. It amazes my coworkers how I can pan and zoom to all of the glitches, but the scope really does all the hard work if you do it right. It literally sticks to the edges and such when it detects you stopping close to them. Excellent piece of equipment. But the acquisition memory makes it all possible!
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.
don't cut it off www.mgmbill.org
I've been a LabVIEW programmer for close to 10 years. I have also been a C and C++ programmer for quite a long time now. I did large projects using both, sometimes using both in the same project. I can call myself a qualified programmer using both languages.
It is perfectly possible to create very large applications, using multi threading and proper design patterns. However, just like you had to spend years learning to write powerful and correct C++, you need quite some time to learn to program LabVIEW correctly.
Once you can do that, writing test and measurement applications can be as efficient or even better than with text based languages. I have the confidence to say that I wrote large data acquisition systems that performed well with very large datasets and high acquisition speeds.
But you have to understand data flow programming, and that is not something you acquire easily, just like you probably sucked at your first text based language projects.
Don't blame the tools for your failure to use them properly.
The 547 is the Barry White of bench top instruments. Its muscular aluminum frame is massive, yet understated. Dual independent time bases tells the ladies you've got a light but agile touch on the trigger circuits.
Truly, this is a scope for a discerning bachelor geek. When you meet an interesting woman, casually mention you've got a type 547 back in your apartment and she's bound to fish for an invitation. Then if later she cannot, in an intimate moment, resist playing with the plug-in unit, propose marriage on the spot.
Post may contain irony: discontinue use if experiencing mood swings, nausea or elevated blood pressure.