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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.
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'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!
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 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."
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! :)