Author Topic: First oscilloscope for third-year EE student  (Read 877 times)

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Offline Someone

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Re: First oscilloscope for third-year EE student
« Reply #25 on: Yesterday at 06:03:40 pm »
I was very surprised to see 60dB dynamic range on the Keysight at uni because that one also has just an 8-bit ADC. I wonder what trick they pulled there.
There is no trick, just very common misunderstandings of what Fourier transforms do to the signal:
https://www.analog.com/media/en/training-seminars/tutorials/MT-001.pdf
 

Offline Fungus

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Re: First oscilloscope for third-year EE student
« Reply #26 on: Yesterday at 06:11:25 pm »
Yes, but if I go to checkout it calculates about €60 in shipping and handling fees and the ToS say I am responsible for paying the VAT (21%) myself :-/ . You don't think the €480 offer for the Instek in Germany is acceptable?

I just remember them being a lot cheaper a few months ago. Now they're hard to find and it looks like the price went up.   :-//

« Last Edit: Yesterday at 06:45:50 pm by Fungus »
 

Offline nctnico

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Re: First oscilloscope for third-year EE student
« Reply #27 on: Yesterday at 06:14:26 pm »
As RedFantom is unfamiliar with this forum it's probably good to note that member nctnico is a bit of a GW-Instek fan.
That is incorrect. GW Instek is a manufacturer which is often overlooked but they have some very decent gear and especially their low end oscilloscopes have several unique features you won't find in that price range. I'm just the voice of the underdog here.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline RedFantom

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Re: First oscilloscope for third-year EE student
« Reply #28 on: Yesterday at 06:34:30 pm »
...
I will make sure to adjust my expectations for the FFT performance. As it is mostly analog circuitry I want to tinker with, I thought the FFT would be really important to see the purity of my signals.
The course that related the dynamic range to the amount of bits of an ADC was only after I had tried the DS1054Z, so I had hoped for something more accurate even though it was unrealistic.

The Keysight with the wavegen would cost me about €250 more than the one without it, and that is still the 2 analog channel only variant (the EDUX1002G). That seems quite steep for the addition... Still, you consider the Keysight a contender here? Because everyone else seems quite convinced that the Siglent and the GW-Instek are the better options, considering I don't really feel comfortable hacking it while it's still in warranty.

I own many oscilloscopes including the Rigol DS1054Z which is full upgraded.  For $330, it is VERY difficult to beat that kind of functionality. It's probably capable of doing 99% of whatever you need right now, it's 4 channels, and it works.  If you're really struggling to afford a fancy scope, save your money and deal with the shortcomings of the DS1054Z.
It is capable of doing most of what I want, but the price difference between the other scopes in the list and the Rigol is not big enough to justify going for the Rigol if I know I am not fully satisfied with it... I bid less than €250 on a DS1054Z on Marktplaats (Dutch eBay), but it was snapped up within minutes :( . For that kind of money, it would be a no-brainer and I'd live with the limitations. I could even get an AD2 and still have money left over. Unfortunately, that was the only real digital oscilloscope that seems worth getting I've seen on there in the months I've been watching it.

...
The marker functionality is new since the big PDF review that I somehow missed until yesterday. That review contained lots of detail on the FFT function, and it is looking much, much better than the one on the Rigol. The fact that they keep updating the software is pretty awesome.

I was very surprised to see 60dB dynamic range on the Keysight at uni because that one also has just an 8-bit ADC. I wonder what trick they pulled there.
There is no trick, just very common misunderstandings of what Fourier transforms do to the signal:
https://www.analog.com/media/en/training-seminars/tutorials/MT-001.pdf
:o I wish they had given us this reader during the course during which they gave us the formula. This is great!

I just remember them being a lot cheaper a few months ago. Now they're hard to find and it looks like the price went up.   :-/
That is annoying. I bought the Rigol then because it was the cheapest I could find that fit my criteria (or so I thought, anyway).


Right now I'm leaning heavily towards the Siglent, because on that one the serial decoding is included and on the GW Instek the hacking of it seems a bit involved. Considering that the Siglent is only €30 more, it seems like the more reliable choice.

A big thanks to everyone who gave their opinion already! I'm planning to order after upcoming Friday (then I have the exam I should be studying for right now), so in the meantime, if anyone has anything to add, please let me know!
 

Offline rsjsouza

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Re: First oscilloscope for third-year EE student
« Reply #29 on: Yesterday at 06:40:43 pm »
As RedFantom is unfamiliar with this forum it's probably good to note that member nctnico is a bit of a GW-Instek fan.
That is incorrect. GW Instek is a manufacturer which is often overlooked but they have some very decent gear and especially their low end oscilloscopes have several unique features you won't find in that price range. I'm just the voice of the underdog here.
Ok, anti-Siglent advocate then? :-DD

Admit it, with a sentence like that you are sounding exactly like Wuerstchenhund and his reason to advocate for LeCroy so fiercely over the years.

IMO there's nothing wrong with that, given it brings different angles to the discussion. But it gives the OP an idea on where the tip scales (the reason for Mr Scram's post).
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Oh, the "whys" of the datasheets... The information is there not to be an axiomatic truth, but instead each speck of data must be slowly inhaled while carefully performing a deep search inside oneself to find the true metaphysical sense...
 
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Offline Fungus

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Re: First oscilloscope for third-year EE student
« Reply #30 on: Yesterday at 06:46:21 pm »
If it comes down to a choice between that and the Siglent for the same money? Most specs are about the same so it's going to be a personal choice. The Siglent has a higher sample rate but the Instek has a much nicer user interface (separate channel controls, a proper button for menu selections instead of pushing a twisty knob... etc).

You rejected the Rigol DS1054Z because of its user interface so what's your true priority?  :popcorn:

 

Online blueskull

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Re: First oscilloscope for third-year EE student
« Reply #31 on: Yesterday at 06:47:28 pm »
Still, you consider the Keysight a contender here?

If you can afford it, then yes. I'm single, so I have money to spare. YMMV.

Besides, if you are budget constrained, seriously, consider Analog Discovery 2. For up to 5MHz digital signal (in scope mode, higher in logic analyzer mode) or 10MHz analog signal, it performs better than any big scopes thanks to its 14 bit resolution.

I have more than $100k MSRP of gears on my bench, yet I always have an Analog Discovery on my bench and I use it the most.

Even if you regret buying it, since you can buy it at academic price, you can easily recover at least 100% your cost by selling it here.
 
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Offline tautech

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Re: First oscilloscope for third-year EE student
« Reply #32 on: Yesterday at 06:51:57 pm »
If it comes down to a choice between that and the Siglent for the same money? Most specs are about the same......
:wtf: have you been drinking !  :scared:

50 MHz BW = 100 MHz BW ?  :bullshit:
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Offline Fungus

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Re: First oscilloscope for third-year EE student
« Reply #33 on: Yesterday at 06:55:55 pm »
If it comes down to a choice between that and the Siglent for the same money? Most specs are about the same......
:wtf: have you been drinking !  :scared:

50 MHz BW = 100 MHz BW ?  :bullshit:

300Mhz after hack = 200Mhz after hack.  :-//

 
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Offline 2N3055

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Re: First oscilloscope for third-year EE student
« Reply #34 on: Yesterday at 07:52:48 pm »
AD2 is whole mini lab in a box. very useful.
Siglent has 2x1 GS/s A/D converters. Big difference. And they keep on upgrading software.
There are also Micsig tablet scopes. Portable, decent performance.

Decide what you need NOW and get that, saving as much money as you can. Or get something else you might need, like multimeter, probes etc etc

During years you will acquire more than one scope. Also, "I want to buy something really good and keep it for years " mentality is dead. Get over it.
Rigol MSO5000 scope would be deemed impossible just 2 years ago.
Buying something "good to last you 10 years" means you will pay more for something that will be outdated in 5 years..

Also predicting future is not very reliable. Newer buy anything you "might need". It's a quick road to bankruptcy and insanity..
 
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Offline edigi

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Re: First oscilloscope for third-year EE student
« Reply #35 on: Yesterday at 09:44:44 pm »
All cheap Chinese/Taiwanese 100MHz/1Gsps scopes are based on HMCAD1511 ADC, which has an ideal SNR rating of 49.8dB. In a real circuit (especially with cost-saving AFE and PLL), you get ~40dB of that.

FFS, that ADC is DESIGNED for cheap scopes.

So getting 35dB spur on FFT actually makes perfect sense.

Luckily this is not true.
Doubling the FFT points decreases the noise floor by 3dB. For details check this:
http://literature.cdn.keysight.com/litweb/pdf/5988-4368EN.pdf

About the FFT: I was very surprised to see 60dB dynamic range on the Keysight at uni because that one also has just an 8-bit ADC. I wonder what trick they pulled there.

See also the above.

Thus an entry level scope with 1M point FFT can have better than 100dB dynamic range in the FFT output (naturally time domain is restricted by ADC, so this is true only for the FFT output). Roughly 60dB comes from the use of FFT.
If averaging is possible this can be even further improved.

Naturally it's better not to overrate any single capability of a scope (be it FFT or Bode plot or whatever; e.g. I've used Bode plot in school only, decades ago).
Choose what best suit for your needs. If you don't know, probably you don't need the capability that you've missed and in the worst case you have to swap. Nowadays even the entry level scopes are very capable.
Checking signals in frequency domain DSA can be a better tool (out of your current budget and scope is indeed the first most important tool).
Most scopes that have very capable FFT have terrible UI that is a pain to use (missing start/stop or center/span type control, number of FFT points controlled by time base and so on).
 

Offline RedFantom

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Re: First oscilloscope for third-year EE student
« Reply #36 on: Today at 12:18:39 am »
You rejected the Rigol DS1054Z because of its user interface so what's your true priority?  :popcorn:
If I pay extra for a user interface that I actually enjoy using and responsiveness, that's worth it to me. I understand that the budget scopes are not as capable as the expensive ones, but not separating your UI updating from your data fetching in the software like the Rigol seems to have? No, that's a deal-breaker.
The joined channel controls are not something I think will bother me. The Keysights also don't have the buttons on the right of the screen, so I'm already used to not having those ;) . It feels like choosing the GW Instek and the Siglent will involve some arbitrary factors. I like the look of the Siglent better... :palm:

Even if you regret buying it, since you can buy it at academic price, you can easily recover at least 100% your cost by selling it here.
I've never seen the AD2 second-hand on the local market, so I'm not sure it would even sell. The NI myDAQ is going for about €80, but that is because one of the Universities in The Netherlands requires it.
The impedance analyzer is another very interesting feature, even if it requires another add-on board. Still: Right now, I have the money and all of it is 'allocated' for buying an oscilloscope. Everything I don't spend will move to my savings account instead (not that saving isn't smart... But I have the money).

...
That is interesting and incredibly good to know at the same time! I will certainly go over this reader as well when I have the time. The FFT UI of the Siglent, at least, is looking just fine to me. At least, when comparing it to the ones in the University lab. The one thing the Keysights indeed miss is selecting how many points are used manually, and it doesn't even show it :-/ .

There are also Micsig tablet scopes. Portable, decent performance.
The Keysight DSOX3014T at the University also has a touchscreen. I've tried it, but I preferred the physical knobs and buttons. I could adjust them more easily while keeping one hand free to hold something in the circuit or hold a screwdriver.

Nothing is future-proof: I get that. That's not what I'm looking for. I'm not looking for a scope that won't make me drool over the models that will be released next year, and the year after that. There's already plenty to drool over in the €1000+ range, let alone the actual DSOX3014T. All I am looking for is a scope that will facilitate the projects that I have in mind now and then after through my master's degree.


The real question here is: Will the AD2 be able to crunch the projects I have in mind right now and the ideas that I have for future ones? The ones that I currently want to do are definitely possible with the AD2. Some of the ideas I have, though, maybe not... I'll think on it.
 

Offline nctnico

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Re: First oscilloscope for third-year EE student
« Reply #37 on: Today at 01:02:43 am »
The Keysights also don't have the buttons on the right of the screen, so I'm already used to not having those ;) .
That is another positive aspect of the GW Instek: it really is easier to use because of having both vertical and horizontal buttons. I used to own an older Agilent oscilloscope on that doing trivial stuff like setting up decoding was much harder because you need to go through so many menu levels.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline Fungus

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Re: First oscilloscope for third-year EE student
« Reply #38 on: Today at 01:15:00 am »
I've never seen the AD2 second-hand on the local market

Of course not, nobody wants to part with theirs.
 

Offline rsjsouza

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Re: First oscilloscope for third-year EE student
« Reply #39 on: Today at 02:03:42 am »
You rejected the Rigol DS1054Z because of its user interface so what's your true priority?  :popcorn:
If I pay extra for a user interface that I actually enjoy using and responsiveness, that's worth it to me. I understand that the budget scopes are not as capable as the expensive ones, but not separating your UI updating from your data fetching in the software like the Rigol seems to have? No, that's a deal-breaker.
The joined channel controls are not something I think will bother me. The Keysights also don't have the buttons on the right of the screen, so I'm already used to not having those ;) . It feels like choosing the GW Instek and the Siglent will involve some arbitrary factors. I like the look of the Siglent better... :palm:
I suspect you may be disappointed by any budget offer. Despite the more modern variants are more responsive than the previous Rigol generations, they are not comparable with the Keysight DSOX3k, especially if your screen is busy with measurements, multiple channels, decoding, etc.

In this case, I would perhaps try to find a local rep or a demo unit to play before you buy. I suspect this will be hard to do, but at least you may get a feel before investing money on the product. If you can't do that, carefully watch the many reviews on the web and try to make a judgment call.
Vbe - vídeo blog eletrônico http://videos.vbeletronico.com

Oh, the "whys" of the datasheets... The information is there not to be an axiomatic truth, but instead each speck of data must be slowly inhaled while carefully performing a deep search inside oneself to find the true metaphysical sense...
 


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