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oscilloscope

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P_froslie

New Member
Hello,

I plan to buy an oscilloscope, but haven't really used one before. I'm looking for suggestions regarding a good to purchase. Also, I am interested in resources that will help me learn to use one.

Thank you in advance..
 

ronv

Well-Known Member
Most Helpful Member
I have an old Techtronix 465 that I have hauled all over the country for maybe 30 years. There are some times I wish for a digital but you can pick that one up on ebay for $50 now. Short of that get at least 100MHZ and 2 traces.
 

cr0sh

Member
Check here for tips on selecting a scope:

Key tips for using an oscilloscope :: Radio-Electronics.Com

Part of the answer depends on what you are planning on doing with the scope, what kind of signals you are planning on working with (or see yourself working with). You can potentially buy more scope than you'll use (and pay a premium for something you don't touch - scopes aren't cheap, especially buying new). It would be like buying a Ferrari, only to use it to go to the corner store only.

Sometimes, you might find you don't need a scope at all; a lot of electronics work can be done without a scope. Other times (especially if you are doing digital work or protocol analysis), a digital logic analyzer or protocol analyzer may be called for; these are both essentially specialized o-scopes with a multitude of input channels, but they can usually only register logic levels, and how each channel relates to each other (the screens show a display similar to timing diagrams for that you see for some complex digital ICs), but they generally won't tell you that there is a "ringing" on the rising or falling edge of that signal, or what the amplitude/frequency of that ringing is. Protocol analyzers work similar to logic analyzers, but the software in them is geared toward showing not only the traces, but also what the data is that is being read; they also typically have special jacks or dongles to plug in the same type of connectors for the cable/data being analyzed (ie, RS-232 on DB-25 or DB-9, Centronics connector for parallel ports, or DB-25, USB, etc).

For most tasks, though, a simple 2 channel scope will work fine; if you can afford a 4-channel scope, go for it, and if you can afford a standalone digital scope, even better. For most hobbyist purposes, a 2-channel analog scope 60-100 MHz will work fine, and a 2-channel digital scope in the same range could be better, depending on the needs. If you can go four-channels on such a digital scope, even better (it can work as a form of logic analyzer in a pinch, if your needs are small). Anything beyond 4-channels and 100 MHz gets expensive very quickly, so keep that in mind.

Brands - if you can afford it, I would pick Tektronix or LeCroy; I have heard both good and bad things about HP scopes (interestingly, though, only good things about their power supplies).

To learn how to use one, it is best to have a scope in front of you. Just about every scope I have seen or heard about had a built in test signal; you should also try to get a small function generator to learn with (so you can use it to learn the scope, see various frequencies and waveforms, understand the graticule lines and relationships to frequencies and voltage levels, etc). In the meantime, you can start here:

Oscilloscope Tutorial Support : Tektronix

Also do a search on google for "oscilloscope tutorial" - you'll find a lot of other links to help...

Good luck! :)
 

cr0sh

Member
One more thing - be -very- careful when shopping for a used scope; some scopes haven't been calibrated in years, or have been banged up, etc - and so you don't know if what you are reading is the true reading, or off in some manner. Calibration of a scope isn't cheap, nor easy (and the equipment to calibrate a scope can cost way more than the scope itself), although some manuals will tell you how to do it if you have access to a -calibrated- calibration frequency generator (that's the expensive part!). I would only trust to purchase a used scope if it was in front of me, so I could see how it showed its trace, and whether its test signal that was output matched the graticule lines and what they indicated. Digital scopes tend to be better in this regard (unless they use an "analog" output tube - that is, drawing the line directly as a vector signal, rather than as a raster-scan CRT display, with drawing handled by software - then there could still be some calibration issues). If you are really unsure, then buy new. As far as the bandwidth is concerned, some will say 5x what you will measure, others will say 2x; but as I noted before, for most uses 60-100 MHz will work fine (heck, for much hobby work, a cheap 20 MHz scope will do). You have to define first, though, what you will be measuring or planning to measure, then use that to help select a scope. You can spend anywhere from $50.00 to $10,000 (or more!) on a scope; you don't want to spend $2.5K on a scope only to find out later you could've done fine with a $500.00 scope...unless you enjoy spending money, of course! ;)
 
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