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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?"
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.
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.
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
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.
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
Get a job someplace that has all the toys you want to play with.
A new Tektronix oscilloscope will work as well. When I was an undergrad my colleagues were convinced that you need analog ones to make proper measurements, but I've had great success using digital ones. I actually prefer them.
Without a definition of what "good" means or what your needs are, I don't think that anyone can give you any sort of advice. I personally would never use one that had to be controlled through a PC. Having to drag a laptop or something all around the electronics of an experiment would be a major pain. (I've only used them in the context of the detector and apparatus signals in physics experiments.)
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 never found one I liked. They all seem very limited in the kinds of probes you can use, the triggers, or the refresh/display. I'm a software guy, so it's not like I am a hardware expert looking for some obscure features.
The best I've used are the ones with ethernet where you can access the data via an AJAX enabled webserver. Then zoom, pan, etc. It's all very slick and worked fine in a non-IE browser (Firefox), this gave me some PC access so I could show others the data I've collected, take screenshots, etc without having to swap a USB drive. If you get an older scope without networking, get one with USB or CF. Having a copy of your data is pretty important, and being able to paint on a picture to describe what you see to others is vital.
Actually, there's at least company with open hardware oscilloscopes:
http://www.bitscope.net/.
coding is life
I got a Tektronix 2432 on Ebay for less than $200 with 4 probes. The 2432 is a 300MHz capture scope that is not as well known as other older Tektronix scopes so it can be bought often very cheaply. People confuse it with a 2445 which is older and not a capture scope.
But first, you have to think about what you will do with a scope. I am a computer engineer and use my scope infrequently. When I was working with video I used it more often and when I build my own uController projects I often have to debug my PCB layout. But most times I could use a good multimeter or a counter. Another option is to use the uC itself as a scope. Data logging can be a problem if you want a lot of samples with a uC with limited memory.
But I agree, when you need a scope there is no substitute.
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
It's also worth pointing out that Rigol apparently makes some of Agilent's low-end scopes for them, so the fact that they aren't a household name doesn't mean all that much.
The Rigol scope has a lot of nice features that you wouldn't expect to find on a cheap scope -- it can take screenshots and store them to a USB thumb drive or print them to a USB printer, you can connect it to your computer to control it or acquire data via USB or RS-232, etc. It actually oversamples at 1 Gigasample/second -- there have been a number of EEVblog shows about it, talking about its performance, the parts that go into it (and the corners they did cut to get the price down!), etc. Google "eevblog rigol" to find the rest of them.
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.
I agree with Andrew. I like having a stand alone instrument that data can be sent to the PC. It really depends on what you're going to be doing as to what you should buy... For $2k you can get a great deal on a used one (like from ebay) but you'll need to do some research first.
Dave does some good reviews here:
http://www.eevblog.com/episodes/
... 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.
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 work for Agilent. Trust me. They still call them scopes...
And for the original poster, be sure to check out how many waveform per second the scope can store. That is the reason that some people do NOT like digital scopes is that they first used a digital scope that cannot trigger and re-arm again in a reasonable period of time. Let's assume that you have a waveform that has an occasional glitch, but you can't set a trigger for it, so you have to catch it by chance. If your scope can capture 10,000 waveform per second, you stand a 10x greater chance than one that can only capture 1,000 waveforms per second. I believe that Agilent wins in this category.
"-1 Troll" is the apparently the same as "-1 I disagree with you."
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! :)
$2000 is a LOT to spend on a scope if you have to ask such a question. Depends on the specs you need, but I'd get a cheaper one and spend the rest of your money on some other gear. The Rigol DS1052E at $400 is by far the best bang-per-buck. I have a review of it, a teardown, and info on how to hack it to a 100MHz version here: http://www.eevblog.com/2010/03/31/eevblog-70-turn-your-rigol-ds1052e-oscilloscope-into-a-100mhz-ds1102e/ http://www.eevblog.com/2010/04/18/eevblog-77-rigol-ds1052e-ds1102e-oscilloscope-hack-update/ http://www.eevblog.com/2009/10/12/eevblog-37-rigol-ds1052e-oscilloscope-teardown/ http://www.eevblog.com/2009/07/19/eevblog-19-rigol-caught-with-their-pants-down/ http://www.eevblog.com/2009/04/05/eevblog-1-rigol-ds1052e-oscilloscope-reviwed/ I also compare PC based and bench oscilloscopes here: http://www.eevblog.com/2009/06/17/eevblog-13-part-1-of-2-digital-storage-oscilloscope-tutorial/ and http://www.eevblog.com/2009/06/17/eevblog-13-part-2-of-2-pc-based-digital-storage-oscilloscope-comparison/ There is no need to get a PC based oscilloscope unless you have a specific need for one. Regards Dave EEVblog
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 like the Tek 2430/2432/2440 scopes a lot, and used one for years in conjunction with a 2467, for those cases where analog-scope performance was needed. Apart from a few considerations like record length, this combination could easily stand up to any DSO costing less than several thousand dollars.
With the 2430-series scopes, the key points to watch out for are 1) make sure it passes its power-up self tests, as the CCD chips used for acquisition are no longer available; 2) avoid the original 2430s with no GPIB port if you think you will ever want to record screenshots from it; and 3) always use an external fan to cool the chips on the main board when servicing it. These scopes seriously stretched the performance envelope available at the time, and those custom chips can be replaced only by buying a parts mule.
Of course, if good ones are going for $200 with probes, it's probably a good idea to just go ahead and spend another $50-$100 on a parts unit to go with it...
Dahlmann tightly grips the knife, which he may have no idea how to use, and steps out into the plain.
Yes, I agree too to this statement. I'm doing fancy hardware design has hobby designer with 6 layer boards, tiny SMD components and 7mil wires. Scope is needed to bring up a new hardware. But for this you can buy one from the cheap ones of LeCroy, Tekktronix or others. If you are planning to use high speed buses like PCI or others then you would need better equipment which are normally not affordable for hobbiest.
I also agree that an protocol analyzer is a must to have like usbee or others to analyze SPI, UART, I2C etc.
Those are the buses which a hobbiest are normally use.
I have a mixed scope at home which I bought for half price from Agilent years ago.
When I need a better scope then I take the one from my company.
Try to speed the money in other tools like good solder station, rework station, reflow ofen etc.
The following measurement equipment is a must to have.
- Scope At least 100MHz with good trigger fuctions
- Multimeter (at least two) Agilent or Fluke got really good ones
- Bus Analyzer. Various from 150$ to thousands of $
Try to write down the requirements of your hardware projects.
What do I need and what can I afford.
Then you will realize what Scope is the best for you.
Good look.
Cheers
J
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.
Our calibration company seals up all edges of the device that give access to its insides after it has been calibrated. Break those seals, and you're in trouble... they'll refuse to calibrate it in the future because of the risk it's been altered. This is forgiven if you provide paperwork from the OEM that they themselves did the repair on the unit.
I don't know that all calibration houses are this strict, though. You could probably find one that would pass your modified instrument if you really wanted.
Despite the rather "textblock"ish formatting of the above post, I do believe that the Rigol DS1052E is one of the best entry-level choices right now, and is GREAT bang-for-the-buck. I have one and it has proven very useful. My only regret is that I purchased it before it got price-dropped to $400. (I paid around $530 plus New York State sales tax from Saelig.)
FYI, Rigol is the manufacturer of Agilent's entry-level units at this point.
To the article poster: You indicate you've done some looking and have been unhappy with what you've found. What have you looked at and in what way have you found it lacking? What are your requirements?
Strangely enough, the "PC-only" units, while you would expect them to provide more bang for the buck, almost universally are inferior. There's a horrible trend in that market to advertise high analog bandwidths without the samplerate to back up that bandwidth. General rule of thumb is that a good scope needs 10x its analog bandwidth in samplerate to capture transients. You're probably OK with only 5x. Many of the PC-based scopes don't even meet the Nyquist criterion! (The Nyquist criteria pretty much lets you capture a sine wave at the analog bandwidth. Keep in mind the analog bandwidth is usually a cutoff frequency, and it can get information from higher frequencies.)
retrorocket.o not found, launch anyway?