Looking for tips to buy a used oscilloscope

Hi,

I want to buy preferably a used oscilloscope as a part of my growing hobby lab. I don't want to break the bank, but want a decent used one.

What features/ brands should I look for? I do not mind if it is analog, as this can get me more features or speed for the price. Maybe sites that can help me make an informed decision?

Best wishes to all.

Any 'scope is better than no 'scope! ;)

I don't have one at home. I never needed one badly enough to spend that kind of money. At work we have some Tektronix digital 'scopes that we got used. I don't know wht we paid, but it's more than the average hobbyist would want to put-out. (maybe a few thousand dollars).

A digital 'scope is nice for digital electronics... Not because it's "digital", but becaue it's better at capturing/displaying non-repetitive, infrequent, or one-time events.

For example, if you have a pulse that's a few microseconds wide and it happens once per second, the trace on an analog 'scope will go-by very fast and only once per second, so the display will be dim. A digital 'scope will keep the waveform in memory for a clean-constant display between triggers. For similar reasons, low-frequency audio waveforms tend to flicker on analog displays.

And, a 'scope with an LCD display is smaller,lighter, and more portable than one with a CRT. That could be important if you don't have a permanent workbench setup and you'll be storing it in a closet/cabinet.

Decide how much you want to spend.

Low-end Rigol Digital scopes are actually an Agilent design. So you may be able to get a really good scope for less than $400.

Keep in mind that used Analog scopes are repairable, but used digital scopes are not.

[quote author=James C4S link=topic=194622.msg1437517#msg1437517 date=1382410454] Decide how much you want to spend.

Low-end Rigol Digital scopes are actually an Agilent design. So you may be able to get a really good scope for less than $400.

Keep in mind that used Analog scopes are repairable, but used digital scopes are not. [/quote]

You have it backwards. A few of the low end Agilents are designed and made by Rigol. I'm not sure how true this is anymore but it was true around 2010. Thats several years ago, which is an eternity in the tech world. Similarly, the low end LeCroy WaveAce series are actually designed and made by Sigilent. The only difference are the colors in the UI. Basically, Agilent and LeCroy outsourced their budget stuff so that they could focus on where they excel: the high-dollar high-end stuff.

Also, not ALL analog scopes are repairable. Some of the later analog Tek's had custom ASICs which are now unobtannium. If one of those blows, the scope is toast. On the complete other hand, I have an old Tenma 20MHz that is entirely discreet components.

My current scope is an enormous boat anchor of a scope a LeCroy 9410 two channel 150Mhz (100MSa/s single shot, 4GSa/s interleaved) with FFT and a few other functions.

This brings up a few points that the OP needs to answer: Space considerations - Old scopes can be VERY large from the size of a large shoe box to the size of a travel trunk depending on the model. The newer low end ones can be much much smaller. CRT/LCD - CRT based scopes are much larger, subject to burn-in and are much heavier. LCD's do not have any of these problems. That being said, CRT's excel in showing small fleeting glitches. The phosphors can show small faint signals which would be lost on an LCD. Connectivity - older scopes had little or no way to get data from the scope to a computer. If its full analogue your only means is to take a photo. Eventually GPIB came about for data transfer but its cumbersome to setup and adapters can be costly. The more recent scopes will have stuff like USB and ethernet conectivity. Signal speed - how fast do you really need. A 100Mhz analog scope will often be able to display glitches and what not of much higher than 100Mhz. A digital scope will not as it is typically limited by its sample rate, not its analog bandwidth. This brings up an important fact. In digital scopes, the most important feature is the sample rate. In particular the single shot sample rate. You typically want a sample rate of 10x the signal bandwidth in order to properly resolve the signal. So for a 100Mhz scope you would ideally like a single-shot bandwidth of 1GSa/s. Cost - You make no mention of price point. For some, the budget is $1000, for others $500, yet others $200 and for some $100. Logic analyzer - often times people working on digital systems think they need a scope. They don't. What they need is a logic analyzer. These often have 16 or more channels which keep track of the 1's and 0's of the state. They are very useful for spotting bugs in a digital device. There are oscilloscopes with integrated logic analyzers, these are often called mixed signal oscilloscopes. Other features - if you go digital you need to pay attention to things like wavepoint memory (the more points it can store the better detail you can get or the father back and forth you can scroll).

Long list of names to look for (in no particular order): Tenma Rigol Sigilent Hantek Owon LeCroy Agilent/HP Tektronix Fluke (aka Philips) Kikusui Anristu Hameg Iwatsu Siemens BK Precision Instek Hitachi Leader

That should cover all of the major brands both old and new (plus some more minor ones).

PedroDaGr8: A few of the low end Agilents are designed and made by Rigol.

No. I was one the people who made the business decision.

As I said the design is Agilent. The manufacturer is Rigol.

Disclaimer: I was an Agilent Employee. In the oscilloscope division...

I just watched a video about what to look for in a scope.

1- Analog bandwith... 50mhz or above is decent I hear 2- At least 10x analog bandwith sample rate AS per Pedro 3- decent waveform memory.

I will try to find one below 400$, hopefuly closer to 200 :)

I hear Rigol, Tecktronic are good. Any suggestions on brands and models?

James, you seem to be in the know. Any suggestion on agilents or Rigols?

If your budget is $200, save up to a $400 budget...

My 2 cents...

If you want to go with an old analog or digital scope, search out for something made by Tektronix, HP (and/or older Agilent), or Fluke. Anything else may or may not be worth your time and money (if you see a good quality heathkit - that would be one potential exception).

For such scopes, in very good working order with leads, expect to spend about $200.00, for around 100 MHz and dual-channel. Anything beyond 100 MHz or dual-channel will start rising in price very quickly - though if you are careful (ie - shop a hamfest or two) - you can find such scopes going for under $500.00.

Make sure you understand exactly how a scope works, and how to test it (with it's built-in test signal) - and what all the controls mean - so you can put it through its paces before you plunk down your cash. That's right - if you plan to buy one of these used, you want to be able to test it first; you can easily get a pig-in-a-poke if you don't. So don't shop ebay for one of these things; Craigslist, garage sales and/or local hamfests only.

Also - here's something of note - I own a Fluke Combiscope - it's a 2-channel DSO scope, with true-analog output; what that means is that it can output to it's CRT one channel as true analog, while the other channel is sampled digital. It's kinda old though, so it doesn't have much storage memory, but it is a unique kind of scope.

Otherwise, save your money, and get one of the Rigol's or other such digital scopes out there; also, if you don't have much experience with a scope, Tek has a very nice tutorial PDF on their site that, while geared to their equipment, is actually general enough to teach you most of what you need for any scope.

Finally - learn what and why you may want/need an isolation transformer - or, just be aware that you don't want to try to measure the AC power signal on the same circuit that your scope is getting it's power from, unless you know -exactly- what you are doing (ie - how to prevent the magic smoke from escaping a fairly expensive tool).

I suggest you buy brand new digital Rigol scope. I bought brand new one - model DS1102E and paid either $299 or $399 for 100 MHz scope (don't remember exactly - it was over a year ago). The 50 MHz scope was $50 less. It was brand new, which means everything works as it is supposed to. It is small and very light, easy to move and does not gobble a lot of spce. When you buy used one you must be familiar enough with the scopes to be able to test it. Beware of the e-bay stuff.

Look at GW Instek also, made in Taiwan instead of China. I got a 4 channel, 200 MHz unit recently and am very pleased with it. http://www.gwinstek.com/en/product/productdetail.aspx?pid=3&mid=7&id=1349

My mainstay is a Tec 2213 60 MHz 2 channel analog scope I got on Ebay… 6 month’s out of calibration for $55.00 about 4 years ago.

Doc