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Help selecting an Oscope
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Help selecting an Oscope

by bobobano on Fri Jun 11, 2010 9:40 pm

Greetings all, I'm trying to select an o-scope and am trying to decide between a PC scope or a digital one (I need something small enough for me to move between home and school). I was also wondering if anyone had any opinions about those saelig scopes?
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Re: Help selecting an Oscope

by macegr on Sat Jun 12, 2010 12:25 am

Unless you really really need something very tiny, go with a standalone scope.

You can pick up a decent 100MHz analog scope for about $100. It'll be heavy and you won't be able save and inspect nonperiodic events. We have a Tek 465B still going strong.

Several places, including Saelig I believe, sell the Rigol DS1052E. It's officially a 50MHz DSO but you can do a simple hack to make it 100MHz. I have one and it works well. Decently portable and well worth the $400 range pricing.
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Re: Help selecting an Oscope

by chatham on Sat Jun 12, 2010 3:08 am

I just recently picked up a little Hantek number off of e-bay for around $150. It's a USB scope, and I've found it really handy as an entry-level job. That said, I'm thinking more I maybe should have gotten a logic analyzer instead, since I use mine to debug digital signals, and while I've been just stopping the scope and hoping to be on the right part of the communication, it's a bit cumbersome.

I guess have you ever used a scope before? I hadn't, and so I imagine there are some features in better scopes that are useful, but I don't know about them, so I'm pretty happy. I do wish my scope had some level of data logging, but for $150, it's hard to complain. I also do a lot of traveling with my projects, and having something that I can easily put in my carry-on and not take up much space is great.

Besides, I figure that the market for used scopes is pretty high, so when I move on to a bigger and better one, I can probably get at least a hundred bucks for this one, as long as I don't do anything crazy to destroy it!
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Re: Help selecting an Oscope

by pm6041141 on Sat Jun 12, 2010 8:05 am

USB/PC based scopes are pretty useless. Get an older Tektronics for around $400. A scope will be the best thing you ever buy.
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Re: Help selecting an Oscope

by mojo on Sat Jun 12, 2010 7:50 pm

I second (third?) a cheap second hand analogue scope.

What worries me about PC scopes is their robustness. A typical analogue scope can take 300V or more and my digital Instek is rated to 350V. You may think "but I'll never accidentally plug it in to the mains" but you could easily give it an ESD shock. Maybe one day you will want to make or test a PSU too.

USB scopes are powered from 5V and many of them won't take signals much above that. Even the ones that do can't have that much protection inside them and if they fail then that is potentially your PC that is going to get hit. You also have to contend with shorts and the like. Many audio applications use +-12V so that alone is potentially 24V it may need to cope with.

Also USB scopes tend to be quite low speed. Some of them claim up to 100MHz or more but if you look carefully at the spec it isn't that simple. The software can be a bit rubbish too where as an analogue Tek or HP is going to have excellent controls and flexibility.

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Re: Help selecting an Oscope

by bobobano on Sat Jun 12, 2010 10:11 pm

Thank you for your suggestions, I'm usually weary of buying stuff off eBay (especially electronics) but given the large number of people who have done so successfully I believe I'll look for one there.
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Re: Help selecting an Oscope

by Entropy on Mon Jun 14, 2010 12:23 pm

I have a Rigol DS1052E and am very happy with it.

$400ish from eBay, in the $500-550 USD range from US-based vendors. Not sure what warranty you get with the eBay units.

I purchased mine from Saelig and was very happy with the deal except for one minor thing: The unit drop-ships from a Rigol USA location in the Midwest, not from Saelig in Rochester, NY. A slight annoyance if you're expecting the unit to arrive overnight and getting hit with NYS sales tax. (I live in New York State, close enough to Rochester that UPS Ground is effectively overnight.) I would still, however, order from them. Just don't make the "it'll come overnight even if I order ground shipping" assumption based on Saelig's location as that is not the ship-from location.

If you're outside of NYS, Saelig is an even better deal.
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Re: Help selecting an Oscope

by FazJaxton on Tue Jun 15, 2010 2:21 pm

I second the Rigols if you're wanting to buy new. I was also leery of buying used, so I bought the Rigol 1052D, which is the same as the E, except with a "logic analyzer" pod, which can show 16 digital signals in addition to the 2 analog signals. It's very useful for debugging SPI or other digital signals.

The Rigol feels very much like a little brother to the Agilent, but much cheaper. I find it excellent for hobby use, if you can afford it. I got mine from Tequipment, which had good service and shipping.
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Re: Help selecting an Oscope

by Entropy on Wed Jun 16, 2010 10:31 am

FazJaxton wrote:I second the Rigols if you're wanting to buy new. I was also leery of buying used, so I bought the Rigol 1052D, which is the same as the E, except with a "logic analyzer" pod, which can show 16 digital signals in addition to the 2 analog signals. It's very useful for debugging SPI or other digital signals.

The Rigol feels very much like a little brother to the Agilent, but much cheaper. I find it excellent for hobby use, if you can afford it. I got mine from Tequipment, which had good service and shipping.

Not surprising here - Agilent's lower-end scopes are made by Rigol.

In fact some of Rigol's other models are 1:1 matches with Agilent units. (I forget which, but someone opened the firmware update file for an Agilent unit in a hex editor and it contained numerous references to a Rigol unit that looked the same.)
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Re: Help selecting an Oscope

by bootstrap on Sat Jun 19, 2010 12:31 am

mojo wrote:What worries me about PC scopes is their robustness. A typical analogue scope can take 300V or more and my digital Instek is rated to 350V. You may think "but I'll never accidentally plug it in to the mains" but you could easily give it an ESD shock. Maybe one day you will want to make or test a PSU too.

USB scopes are powered from 5V and many of them won't take signals much above that. Even the ones that do can't have that much protection inside them and if they fail then that is potentially your PC that is going to get hit. You also have to contend with shorts and the like. Many audio applications use +-12V so that alone is potentially 24V it may need to cope with.

Also USB scopes tend to be quite low speed. Some of them claim up to 100MHz or more but if you look carefully at the spec it isn't that simple. The software can be a bit rubbish too where as an analogue Tek or HP is going to have excellent controls and flexibility.

I must admit I haven't looked at many PC scopes, but I just bought one after having exactly this conversation with the manufacturer (picoscope 6403 kit). They claim the only thing that could seriously damage the scope is "plugging it into 240V mains", thus anyone in 120V land is safe. Also, they have several voltage ranges (that you set from the GUI, just like from the front panel of a conventional oscope) that spans from microvolts precision to over 100 volts. Maybe this isn't typical of PC oscopes, but at least "not all of them" are as frail as your warning (or so they claim).

I too would rather have a conventional oscope, but the oscope I ordered costs about half what a conventional oscope would cost with the same performance... plus I get to view the display on my 24" diagonal 1920x1200 monitor, which conventional oscopes can't match (that I know of).

So, better check what the actual comparisons are before you decide.
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