Buying an Oscilloscope

April 16, 2008 6:28 AM

I'm an electrical engineering student/hobbyist looking to buy an oscilloscope. I'd like to spend around $200 ($300 max, probes/shipping included). What should I look for, and where?

I think dual trace is worth having to compare signals. I'm not sure what I need bandwidth wise... I don't intend to do much radio work, so 10Mhz seems sufficient (in what other instances would I need more?).

posted by phrontist to technology (10 comments total)

sometimes American Science and Surplus has some good deals. Plus...just down the street from me! Wheepers!
posted by timsteil at 6:37 AM on April 16

In that price range I think you are looking for an old Tektronics or HP scope. The features that you need depend upon the use to which you will put the scope. 10 Mhz is probably fine for finding noise in circuits (what I use mine for) and general non-radio work. 100 MHz will handle just about anything a hobbyist would want. The big issue is where to get one. Since you are a student I would check with your profs, and I would also ask them for specific recommendations of what you will need etc. They may even be able to point you to a local source or find a way to sell you an old one from the school. eBay is a great resource if you are willing to wait a few months for good deals to come around. Never buy and old scope "as is." They are notorious for showing up with something wrong. Get it guaranteed in working condition, all parts and functions working, when it arrives at your door. You will pay extra for that but it is worth it.
posted by caddis at 7:39 AM on April 16

Oh, I forgot to add, this is a wonderful scope tutorial if you have not already been trained on one at school.
posted by caddis at 7:41 AM on April 16 [1 favorite]

If you are at a bigger school, you may have an campus salvage store where all old equipment goes to get sold off, to recoup the cost of new equipment. You can often find old test equipment there (as well as loads of other neat stuff, like microfiche readers!).
posted by Loto at 8:19 AM on April 16

Are you looking for an analog or digital scope? If analog, mefi-mail me.
posted by adamwolf at 9:07 AM on April 16

You might still be able to get used Tektronix mainframe scopes and plugins for pretty cheap from ebay and the like (beware of shipping costs, they're heavy! and huge!). A scope that was top-of-the-line forty years ago is still a good scope today, if you don't need GHz bandwidth or deep digital capture buffers or the like.

There are also an increasing number of tiny USB 'scope pods that use your computer for display and control.
posted by hattifattener at 10:02 AM on April 16

The best place to find one is a campus cleanup in your electrical engineering department. Sometimes you will still have to pay, but it is likely to be a very good price.

If you have infinite space, tek 7000 series stuff is going very inexpensively on ebay. None of what's up right now looks any good, but this 7613 in the completed items was a good value. This one with a faded display wasn't (at least not for you). I'm not sure why they are so much less popular than they were a few years ago, but I know mine is a lot less popular with me because space is even more of a problem right now.

I picked up a USB oscilloscope (not an endorsement of the seller, just the next to end) a few days ago. I don't have any comment yet, but I expect it will be pretty good. I'm on the fence about the cheaper one. It only has a 50kHz bandwidth, which you can often get yourself with oscilloscope software¹. On the other hand, it is a nice little package, and I'd rather be hooking up to an external device, so if I blow it up my PC will probably live.
¹One example of oscilloscope software. There are lots of choices, I've never used any. That software talks about 0-20kHz, but theoretically the max bandwidth would be ~20kHz, ~40KHz, or ~90kHz depending on your sound card and software combination.

Finally, the oscilloscope guides at ebay are a very good resource!

Okay, finally finally.. There are lots of right answers on this one. I think the rightest answer is to get going with something relatively below your budget and the sooner the better. Learn all you can, and if it doesn't suit you, you can always resell it and try again. You shouldn't be out too much money, and you will be in a much better position to select your next one.
posted by Chuckles at 10:26 AM on April 16

Might be worth adding.. $20 will get you a pair of discount but perfectly useful probes. So, no need to worry if they are included in the 'scope sale or not.
posted by Chuckles at 10:44 AM on April 16

In my circuit analysis class, we've been using an external USB sound card and the Zeitnitz soundcard oscilloscope. It's been adequate for everything we've done in class, and the only costs are 30 bucks for a USB soundcard and the cost of a couple op-amps and resistors for an attenuator circuit. However I'd recommend getting a real scope. The setup we have has various limitations, such as not being able to get a clean square wave--you get a lot of ringing every time the voltage changes state.

I got my real scope (Tektronix 2213, 60 MHz) on ebay for ~250 clams a couple years ago. It works great. I can't offer details, as I am hundreds of miles away from it right now. If you want to see it, go over to my house and get my pop to show it to you.
posted by Commander Rachek at 10:52 AM on April 16

Nobody's mentioned hamfests, so I will. It won't be easy to test the scope out there, plus all the other caveats that apply to buying from random strangers. On the other hand, it's good to keep hamfests alive, if possible. And there's no shipping charges.
posted by Crabby Appleton at 3:10 PM on May 1