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 Posted: Jun 14, 2012 - 09:05 PM |
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Joined: Oct 15, 2010
Posts: 317
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I've been told enough times that I need an oscilloscope, so I guess I'll get one.
I've read several dozen similar threads, but many are several years old and (perhaps) out dated.
With a budget of $450 or less, I know I'm restricted to Chinese models. I read a LOT of people suggesting the Rigol 1052e, and that's fine... but then those same people are quick to call other brands "chinese crap" (etc), but the Rigol is Chinese too so I'm not understanding the bias.
Anyway, I'm fine with getting something that every says to get... but then I see the Aktakom ADS-2111M (aka Owon SDS7102 I think) and am attracted to the much larger (and wider) screen, 10 Mpts per channel memory depth vs 500kpts/ch for the Rigol (that's 20x as much... not that I really understand the significance), included external trigger (whatever that means), and additional math function (divide). Mostly, its the screen that appeals to me I guess. Cost is very similar and under my budget.
I'm also NOT looking at spending my budget if I don't have to! I see things like the DSO Nano and wonder... is that good enough?
So to help with that, you'll need to know what I need it for, right? Honestly, I'm not sure. For the most part, its simple things like confirming a pin is high/low or that I'm generating a PWM of 400hz like I think I am, etc. I can't imagine why I'd need 100Mhz capability... but it'll probably come up some day. I don't want to spend $450 if I don't have to, but I also don't want to waste $100 if I'm going to have to spend $450 later anyway.
Note - in the foreseeable future, I don't expect to work with anything > 20V so I'm not concerned with high voltage ratings.
Cheers.
- Steven |
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Posted: Jun 14, 2012 - 10:07 PM |
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Joined: Jun 13, 2009
Posts: 307
Location: Ann Arbor, MI
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I picked up a PM3394A Philips 200MHz scope off of craigslist for like $400 complete with a recent calibration sticker! The thing doesn't stop working, analog and digital modes, and every other peripheral you can imagine. I didn't like the idea of used first, but it seems to work awesome and I'm sure I could have beat the seller down lower on his price if I wanted to. I believe this scope new went for a few thousand and it hadn't hardly been used...
Here's my Oscope thread from last year, the geniuses told me what speed I need based on the types of signals to analyze somewhere in it. It's all about rise time and having a scope be 10 times faster is what I think someone said...
http://www.avrfreaks.net/index.php?name ... highlight= |
Last edited by smkipus on Jun 14, 2012 - 10:09 PM; edited 1 time in total
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Posted: Jun 14, 2012 - 10:09 PM |
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Joined: Mar 19, 2010
Posts: 52
Location: California
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I have two older dual trace tektronixs oscopes (american made). Picked them up from a local electronics surplus store for about $100 each. One is from the 80's (250mhz) the other 90's (100mhz).
I am a hobbyist so they work for me. You might look into the surplus market. |
_________________
I am not encumbered by the restraints of the adult mind.
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Posted: Jun 14, 2012 - 10:58 PM |
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Joined: Oct 15, 2010
Posts: 317
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If something falls on my lap, I'll consider used... I have no particular hangup there. But I'm in a relatively remote area in Canada without easy access to the same kind of markets most Americans enjoy. I suspect I'd be better off getting something new. Just easier if nothing else.
After reading a bunch more threads, I think I'm leaning toward the Owon SDS7102. It got a bad rap early on but it sounds like most issues were fixed over a year ago. I'll check out that thread in case it was something I missed, so thanks.
I still wonder if the "toy" devices like the DSO Nano, etc, are worth considering. |
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Posted: Jun 15, 2012 - 01:49 AM |
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Joined: Jul 02, 2005
Posts: 5951
Location: Melbourne, Australia
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s_mack wrote:
I still wonder if the "toy" devices like the DSO Nano, etc, are worth considering.
Are you planning on "playing" or "working" in the field? |
_________________
Ross McKenzie
ValuSoft
Melbourne Australia
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Posted: Jun 15, 2012 - 02:05 AM |
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Joined: Dec 11, 2007
Posts: 6856
Location: Cleveland, OH
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Quote:
It's all about rise time and having a scope be 10 times faster is what I think someone said...
Yes. If you want to look at a square wave of 10 kHz, the fundamental frequency making up the square wave is a sin wave of 10 kHz. You need to have an adequate bandwidth to see about the first 10 harmonics of the fundamental frequency to adeuately reproduce the waveform in the time domain, i.e. on an Oscope screen.
If the bandwidth isn't wide enough, then the higher frequency components of the signal are attenuated, or lost altogether, and the square wave won't look very square.
I would be reluctant to buy a single channel Oscope. I find that I am often comparing the timing of two signals, or for analog work the input and output of a circuit, and having two channels makes this much easier.
Make sure a good pair of probes are included in the package, or be sure to include that within your budget.
A scope without a good probe is a lot like a radio without a good antenna.
JC |
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Posted: Jun 15, 2012 - 02:19 AM |
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Joined: Oct 15, 2010
Posts: 317
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valusoft wrote:
s_mack wrote:
I still wonder if the "toy" devices like the DSO Nano, etc, are worth considering.
Are you planning on "playing" or "working" in the field?
Excellent question.
I fall in between. And also beside  I have no aspirations of being an EE or even a hobbiest really. I am an entrepreneur. I find niche market needs and I fill them with "clever" products that larger companies either haven't thought of or, more often, aren't willing to bother with because its too small of a market.
More often than not, they involve electronics.
Depending on the project, I hire the design out or I give it a go myself. The determining factors on that decision include: how quickly I want to get to market; how much outsourcing will cost; how big the total value of the project is expected to be.
My projects have varied from industrial washing machines to automotive electronics, where I had my biggest successes. Most recently, I've been working on a few related products for a new hobby of mine - r/c aircraft. These tend to be lower margin items where cost control is critical. As an example, I developed a electro-mechanical for a specific automobile a few years ago. The per-unit cost is aroung $28 and they sell for over $450 - so obviously there was room in there for outsourcing the electronics design (but I am proud to say I learned and did all the injection molded plastics design myself! As well as the PIC firmware having zero PIC experience at the time. I also personally did all the CANBUS analysis, which was considerable - again, with no experience). The last product I did, on the other hand, cost me $18 and I sell them for $35. I've sold 2000 of them so far, but even still had I paid someone $30k to do the design, it wouldn't have been much of a venture! In this case, it was my first foray into AVR and I did the entire "design" myself... however I can't take too much credit, as a good chunk of it was adapted from an openharware project and the rest was pretty much following datasheet typical application circuits. Still, I did it myself.
The future holds more of the same. As I learn things, I build my toolbox as does anyone else. But if I seek to learn it all, then too much time is spent apart from my core competencies - which is management, conception, procurement and, ultimately, sales.
So is that "playing" or is that "working"? I tend to believe I'll always be closer to what you envision as "playing" - I just expect to make good money at it.
- Steven |
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Posted: Jun 15, 2012 - 02:25 AM |
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Joined: Oct 15, 2010
Posts: 317
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DocJC wrote:
Yes. If you want to look at a square wave of 10 kHz, the fundamental frequency making up the square wave is a sin wave of 10 kHz. You need to have an adequate bandwidth to see about the first 10 harmonics of the fundamental frequency to adeuately reproduce the waveform in the time domain, i.e. on an Oscope screen.
that entire paragraph is beyond my brain's bandwidth.
DocJC wrote:
If the bandwidth isn't wide enough, then the higher frequency components of the signal are attenuated, or lost altogether, and the square wave won't look very square.
That, I think, I understood
DocJC wrote:
I would be reluctant to buy a single channel Oscope. I find that I am often comparing the timing of two signals, or for analog work the input and output of a circuit, and having two channels makes this much easier.
I already figured 2 channel would be the way to go unless I was spending "toy" money. I see that 4 channel are just too expensive except for the DSO quad, but again we're back to toys, right?
DocJC wrote:
Make sure a good pair of probes are included in the package, or be sure to include that within your budget.
A scope without a good probe is a lot like a radio without a good antenna.
JC
Thanks for that. How does one tell what is a "good" probe?? |
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Posted: Jun 15, 2012 - 04:00 AM |
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Joined: Jul 21, 2005
Posts: 1373
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I would consider Rigol as a reliable and dependable brand, they OEM for Agilent so their quality must be ok.
I have the Rigol DS1052E, 50 mhz bandwidth. I paid around $400 two years ago. Good scope for the money.
In another thread a few months ago someone posted about this scope, http://www.eevblog.com/forum/general-ch ... -for-free/
It runs linux and is better speced than the Rigol, but costs around $550 USD. If I could do it again, I would get that linux scope.
I do have a few complaints about my Rigol:
-When looking at small signals at DC, at certain amplifications the waveform looks totally fucked up. It looks fine when I use AC.
-Too many functions and not enough buttons, this is probably a common problem with most entry level DSO scopes though regardless of brand. You will eventually bump and grind your way to the right settings provided you push enough buttons.
-The PC software/USB interface to connect your PC the scope is dog slow. It is a complete slideshow. IIRC the resolution you see on the PC screen is the same as on the scope, ~320x240 (I think), you can not even maximize the screen so the image on your PC screen is no easier on the eyes than the LCD on the scope.
I would not recommend getting a used analog scope unless you find something dirt cheap that is local to you, it costs more to ship such a beast than it is worth.
I would also not recommend getting really low end stuff like usb PC scopes and the DSO nano. A scope is a tool, you need something that is of good quality and you also must be confident that it is of good quality.
The Owon does look nice, better than nice, it looks gorgeous, it also has a VGA output and an ethernet lan port. Seems like a winner on paper.
I would suggest you get a Rigol, it will be under your budget, with the extra money get some nice probes or a logic analyser. |
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Posted: Jun 15, 2012 - 04:35 AM |
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Joined: Jun 13, 2009
Posts: 307
Location: Ann Arbor, MI
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| I smile and get dizzy when thinking of one day buying my very own logic analyzer... or better a spectrum analyzer or best a network analyzer |
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Posted: Jun 15, 2012 - 04:38 AM |
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Joined: Apr 28, 2012
Posts: 70
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I've used the Rigol at TechShop, and I'm friends with it. I wouldn't mind having one at home, but I don't pay for one.
For me, I mostly do digital logic, for which a logic analyzer is much better. I ended up buying the Salae Logic (8 channels,) for $149, and it's fantastic! The software works superbly, even in Linux, and it can decode various serial and parallel protocols. For $299 you can get 16 channels instead of 8, if you're into very wide systems.
If you're doing analog voltages that are more of the "control voltage between 0 and 5V" type, and less of the "accurately represented analog signal" type, then a voltmeter, or a cheap pocket or USB scope may be good enough, but the moment you want to actually look at something for real in the analog domain, it won't be good enough anymore. |
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Posted: Jun 15, 2012 - 05:29 AM |
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Joined: Jul 02, 2005
Posts: 5951
Location: Melbourne, Australia
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s_mack wrote:
So is that "playing" or is that "working"? I tend to believe I'll always be closer to what you envision as "playing" - I just expect to make good money at it.
- Steven
Steven,
I would call it "working". Don't short-change yourself or your tools.
Cheers,
Ross |
_________________
Ross McKenzie
ValuSoft
Melbourne Australia
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Posted: Jun 15, 2012 - 05:48 AM |
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Joined: Oct 15, 2010
Posts: 317
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| Fine advice. Still a question of "which one" Now that I'm reading up on logic analyzers... wow, that seems so much more useful for what I've needed a scope for thus far, but I recognize its not at all useful for some of the things I may need a scope for in the future. Are there any that do both? I saw a chart comparing scopes somewhere and there was brief mention in it that the Rigol supported "up to 16 digital channels" but its a 2-channel so I don't get what it was referring to. |
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Posted: Jun 15, 2012 - 06:11 AM |
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Joined: Jan 09, 2007
Posts: 1884
Location: Arlington, Texas, U.S.A.
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DocJC wrote:
If you want to look at a square wave ... You need to have an adequate bandwidth to see about the first 10 harmonics of the fundamental frequency to adeuately reproduce the waveform in the time domain, i.e. on an Oscope screen.
That can get expensive.
Rules of thumb:
1. 0.5/rise-time is enough (maybe more than enough).
2. 5, or preferably 7, times the square wave's fundamental frequency.
3. 10_000USD/GHz.
AVR32's rise-time is approximately 1ns; CD4000-series CMOS is 10ns (IIRC). AVR is in-between those two.
Ref.
Erroneous Harmonics, Dr. Howard Johnson.
Take the Fifth, Dr. Howard Johnson.
Probing High-Speed Digital Designs, Dr. Howard Johnson. |
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Posted: Jun 15, 2012 - 06:24 AM |
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Joined: Jan 09, 2007
Posts: 1884
Location: Arlington, Texas, U.S.A.
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s_mack wrote:
Are there any that do both?
Yes and kinda popular with embedded systems engineers. Use the analog part for signal integrity analysis, triggering, plant's signals (usually analog) then use the logic analyzer part to connect to one of the MCU's 8-bit ports for application debug and the remainder to the board's digital signals. But, I'd use a good scope combined with an off-scope inexpensive logic analyzer and a shared trigger signal. But for field usage, an all-in-one instrument appeals if one can afford the extra cost. |
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Posted: Jun 15, 2012 - 07:03 AM |
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Joined: May 02, 2007
Posts: 3022
Location: Nieuwegein, Netherlands
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s_mack,
as Ross said, consider it work.
This means that you can write it off over a larger period of time and multiple projects.
What good is a scope that is not doing what it needs to do.
I worked at a company where they always wanted things cheap. I needed a scope and I had made a list of features I wanted on that scope to be able to do my job now(at that time) and in the future. I had made a list of 3 or 4 scopes in the 10K euro price range that had all the stuff I knew I needed.
When coming back from a holiday I found a big box on my desk with a scope that was only 8K and lacked a large number of features. reason it was a lot cheaper. After some time I needed to do a lot of measurements and would have saved me a lot of time if I would have had some of the features. I calculated that it would cost me over a month to do all the measurements then as I could not automate things and had to do it all by hand.
The manager then decided that the options needed to be bought ( same manager that first removed the options to be cheaper) cost then of all the options needed 3K and those where not all the options. The director was not very pleased when I had to explain that it was decided that the options where not needed... as it had cost him over 1K in the end. It became even worst when I later needed another option and thus had to pay again.
So trying to save money now on a piece of equipment you are going to use for a long time will be money bad spend in the end.
So you need to think:
- how many analog channels do I need 2 or 4
I would go for 4 most of the times 2 is enough, but I have a 2 channel scope at home and sometimes really lack a 3rd or 4th channel.
- Do I need digital and how many channels
This is then your logic analyzer. I do not have it, but this also is very handy at times and will save you time. Less needed though if you have 4 channel scope.
- what is the highest frequency I need to be able to measure.
Scope suppliers tell us that you need at least 3 times more band with on your scope then you have on your system. But here the trick question is what is your max frequency needed. 20MHz AVR or 150MHz FPGA. This will be a real money maker The higher the bandwith needed the higher the price
If you are not sure, you have to ask for a demonstration. Then you can play with it (having a feeling with a scope and how to use it is also a thing you need to have) nice scope but terrible user interface will also ensure you will not want to use it, hence waste of time as it is needed to save you time in measureing. |
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2)tutorial forum
3)Newbie start here
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Posted: Jun 15, 2012 - 07:24 AM |
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Joined: Oct 15, 2010
Posts: 317
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thanks for that.
Anyone see the QA100? Looks kind of bang-on for what I'm looking for?
"20MHz AVR or 150MHz FPGA"?? I have no idea what an FPGA is so I'm gonna say "probably not". 20Mhz AVR? Sure... why not. But I'm still not getting how that determines the frequency I need in a scope. Can't I take it for granted that my 20Mhz crystal is actually humming along at 20Mhz? Its worked so far without needing a scope. So far, the things people have told me "get a scope" for have been to confirm an output is high/low and to confirm my math was correct on a PWM and it was actually outputting at 400Hz like I thought it was. Beyond that, I can see needing to debug UART signals (9600 baud) or similar, but that's well below uC clock speed. I'm sure I'm missing things. |
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Posted: Jun 15, 2012 - 08:16 AM |
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Joined: May 02, 2007
Posts: 3022
Location: Nieuwegein, Netherlands
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if your crystal is not doing it's thing then indeed you have other problems.
but if you want to measure lets say a 20MHz square wave.
this square wave is build up out of a sine of 20Mhz, 40MHz, 60mHz, 80MHz......
Now if you measure that square wave with your scope of 20MHz the signal will look like a sine wave and not a square wave.
if you have a 100MHz scope it will look like a square wave.
so if you have a problem with a signal that is not getting high fast enough and your scope is to 'slow' then you might think it is because of the signal not being square but only slowly rising, although the square wave is a square wave, but you have a problem in another part of the circuit.
That is why you need a 'fast' scope.
I hope this clarifies a bit. |
_________________
1)Datasheet and application notes checked?
2)tutorial forum
3)Newbie start here
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Posted: Jun 15, 2012 - 04:23 PM |
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Joined: Oct 15, 2010
Posts: 317
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Posted: Jun 15, 2012 - 04:37 PM |
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Joined: Feb 12, 2005
Posts: 16336
Location: Wormshill, England
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jwatte wrote:
I've used the Rigol at TechShop, and I'm friends with it. I wouldn't mind having one at home, but I don't pay for one.
For me, I mostly do digital logic, for which a logic analyzer is much better. I ended up buying the Salae Logic (8 channels,) for $149, and it's fantastic! The software works superbly, even in Linux, and it can decode various serial and parallel protocols. For $299 you can get 16 channels instead of 8, if you're into very wide systems.
If you're doing analog voltages that are more of the "control voltage between 0 and 5V" type, and less of the "accurately represented analog signal" type, then a voltmeter, or a cheap pocket or USB scope may be good enough, but the moment you want to actually look at something for real in the analog domain, it won't be good enough anymore.
I agree 100%. You will use a Logic Analyser. The scope will gather dust.
Of course if your main interest is in analog signals, your mileage may vary.
David. |
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