Author Topic: Gw Instek GDS2204E (200MHz 4 channel DSO) review  (Read 72622 times)

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Online wraper

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Re: Gw Instek GDS2204E (200MHz 4 channel DSO) review
« Reply #50 on: September 16, 2016, 10:59:55 am »
Is it really true that the GDS2204E is newer, has better specs and cheaper than the GDS-2204A?
Yes it's true, except 1GSa/s vs 2GSa/s sampling rate as 2000E are budget series. Also 2000A does not include options by default, and need them purchased separately.
 

Offline eeguy

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Re: Gw Instek GDS2204E (200MHz 4 channel DSO) review
« Reply #51 on: September 16, 2016, 11:13:34 am »
Is it really true that the GDS2204E is newer, has better specs and cheaper than the GDS-2204A?
Yes it's true, except 1GSa/s vs 2GSa/s sampling rate as 2000E are budget series. Also 2000A does not include options by default, and need them purchased separately.

Thanks. Sorry, what do you mean by "not include options by default"? What options?


From the specs:
http://www.gwinstek.com/en-US/products/Oscilloscopes/Digital_Storage_Oscilloscopes/GDS-2000E

Under Real Time Sample Rate: Max: 1GSa/s (4 ch model), Per channel 1GSa/s (2ch model)
What does that actually mean? Does that mean on a 4 ch GDS-2204E model, the max sample rate of each channel is 1GSa/s even when all four channels are used?

Under Trigger, it states that EXT* only on dual channel models. Does that mean I cannot use an external trigger such as a button to trigger on/off the recording on the GDS-2204E?
 

Online wraper

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Re: Gw Instek GDS2204E (200MHz 4 channel DSO) review
« Reply #52 on: September 16, 2016, 11:45:22 am »
Is it really true that the GDS2204E is newer, has better specs and cheaper than the GDS-2204A?
Yes it's true, except 1GSa/s vs 2GSa/s sampling rate as 2000E are budget series. Also 2000A does not include options by default, and need them purchased separately.

Thanks. Sorry, what do you mean by "not include options by default"? What options?

For example:
Quote
I2C/SPI/UART/CAN/LIN Serial Bus Trigger and Decoding Function

Also full memory and other things fully enabled by default. In most of the scopes those need to be purchased separately and often will cost more than the scope itself.
Quote
Under Real Time Sample Rate: Max: 1GSa/s (4 ch model), Per channel 1GSa/s (2ch model)
What does that actually mean? Does that mean on a 4 ch GDS-2204E model, the max sample rate of each channel is 1GSa/s even when all four channels are used?
It means that 2ch will always run at 1GSa/s, 4ch version will drop to 500 MSa/s if more than 2 of any channels simultaneously enabled.
Quote
Under Trigger, it states that EXT* only on dual channel models. Does that mean I cannot use an external trigger such as a button to trigger on/off the recording on the GDS-2204E?
Vast majority of 4ch scopes do not have separate external trigger input. Therefore you need to sacrifice one input channel for this purpose if you need one.
 

Offline eeguy

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Re: Gw Instek GDS2204E (200MHz 4 channel DSO) review
« Reply #53 on: September 16, 2016, 12:29:48 pm »
Is it really true that the GDS2204E is newer, has better specs and cheaper than the GDS-2204A?
Yes it's true, except 1GSa/s vs 2GSa/s sampling rate as 2000E are budget series. Also 2000A does not include options by default, and need them purchased separately.

Thanks. Sorry, what do you mean by "not include options by default"? What options?

For example:
Quote
I2C/SPI/UART/CAN/LIN Serial Bus Trigger and Decoding Function

Also full memory and other things fully enabled by default. In most of the scopes those need to be purchased separately and often will cost more than the scope itself.
Quote
Under Real Time Sample Rate: Max: 1GSa/s (4 ch model), Per channel 1GSa/s (2ch model)
What does that actually mean? Does that mean on a 4 ch GDS-2204E model, the max sample rate of each channel is 1GSa/s even when all four channels are used?
It means that 2ch will always run at 1GSa/s, 4ch version will drop to 500 MSa/s if more than 2 of any channels simultaneously enabled.

Having full memory and I2C/SPI/UART/CAN/LIN Serial Bus Trigger and Decoding functions enabled by default seems to be a good deal.

Given that I am told 1GSa/s should be sufficient for my use, is it bad to have the sample rate dropped to 500 MSa/s if more than 2 channels of the 4 channels GDS2204E is used?

From the Keysight's specs for the 2000X Series:
http://literature.cdn.keysight.com/litweb/pdf/5990-6618EN.pdf?id=2002854

The maximum sample rate is 2 GSa/s half-channel interleaved, 1GSa/s per channel

The 3000T X Series:
http://literature.cdn.keysight.com/litweb/pdf/5992-0140EN.pdf?id=2545408

The maximum sample rate is 5 GSa/s half channel interleaved, 2.5GSa/s all channel

Does that mean for the 4-channel 2000X ones, when all four channels are used, the sample rate for each channel is 1GS/s while for the 4-channel 3000T X ones, when all four channels are used, the sample rate is 2.5GSa/s?
« Last Edit: September 16, 2016, 12:32:02 pm by eeguy »
 

Offline saturation

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Re: Gw Instek GDS2204E (200MHz 4 channel DSO) review
« Reply #54 on: September 16, 2016, 07:23:09 pm »
When sampling rate drops the key problem is aliasing error.  With mutiple channels engaged and I'm concerned about possible aliasing artifacts I intermittently turn one or several of the CH off; this raises the sampling rate instantaneously in real time so I can compare waveforms very quickly, flipping between full and reduced sampling.   Its a simply ploy when using low cost DSO at your home lab versus better gear at work.


Having full memory and I2C/SPI/UART/CAN/LIN Serial Bus Trigger and Decoding functions enabled by default seems to be a good deal.

Given that I am told 1GSa/s should be sufficient for my use, is it bad to have the sample rate dropped to 500 MSa/s if more than 2 channels of the 4 channels GDS2204E is used?


....

Does that mean for the 4-channel 2000X ones, when all four channels are used, the sample rate for each channel is 1GS/s while for the 4-channel 3000T X ones, when all four channels are used, the sample rate is 2.5GSa/s?

Yes.  There are extensive reviews and teardowns in the forum of both series DSOs but I can't recall the details, Keysight DSO do have more ADC to sustain the sampling rate.
« Last Edit: September 16, 2016, 07:51:20 pm by saturation »
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Online nctnicoTopic starter

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Re: Gw Instek GDS2204E (200MHz 4 channel DSO) review
« Reply #55 on: September 16, 2016, 07:41:34 pm »
I did some testing with the GDS2204E and aliasing is minimal because it has anti-aliasing filters in place. With a 200MHz bandwidth the 500Ms/s is more than enough to show the signal. You have to keep in mind that in theory the minimum sampling frequency is twice the bandwidth. Everything more is overkill but in practical situations you need some margin for the anti-aliasing filters.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline marmad

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Re: Gw Instek GDS2204E (200MHz 4 channel DSO) review
« Reply #56 on: September 16, 2016, 07:51:57 pm »
You have to keep in mind that in theory the minimum sampling frequency is twice the bandwidth. Everything more is overkill but in practical situations you need some margin for the anti-aliasing filters.

It has nothing to do with "overkill"; it has to do with design. Out-of-band signals may only be attenuated by 10 dB beyond the band-edge of the instrument, and it doesn't matter what kind of anti-aliasing filters the DSO has, they absolutely don't roll-off infinitely fast and some buffer room is needed.
« Last Edit: September 16, 2016, 07:53:42 pm by marmad »
 

Online nctnicoTopic starter

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Re: Gw Instek GDS2204E (200MHz 4 channel DSO) review
« Reply #57 on: September 16, 2016, 08:04:33 pm »
That is why I wrote: some margin is required. Also the typical passive probing solution will load a high frequency signal way more so there is already filtering before the signal gets into the scope.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline marmad

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Re: Gw Instek GDS2204E (200MHz 4 channel DSO) review
« Reply #58 on: September 16, 2016, 08:19:26 pm »
Reliable sampling and reconstructing frequencies at exactly the Nyquist Rate is physically not attainable, and thus a higher sampling rate is not "overkill"; your precise descriptor which I was responding to.
 

Online nctnicoTopic starter

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Re: Gw Instek GDS2204E (200MHz 4 channel DSO) review
« Reply #59 on: September 16, 2016, 08:41:45 pm »
Again: I wrote 'margin' so don't insist on reading something different!
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline marmad

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Re: Gw Instek GDS2204E (200MHz 4 channel DSO) review
« Reply #60 on: September 16, 2016, 09:01:46 pm »
Again: I wrote 'margin' so don't insist on reading something different!

Sheesh... I'm not reading anything other than your English - which, admittedly, is poor. You can't "overkill" based on a theory, and by "practical situations", you actually mean "real-world applications". It's ridiculous to write posts which might make some people believe that sampling above the Nyquist Rate is irrelevant (i.e. "overkill").
« Last Edit: September 16, 2016, 09:07:52 pm by marmad »
 

Offline Wuerstchenhund

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Re: Gw Instek GDS2204E (200MHz 4 channel DSO) review
« Reply #61 on: September 17, 2016, 10:55:52 am »
Again: I wrote 'margin' so don't insist on reading something different!

Sheesh... I'm not reading anything other than your English - which, admittedly, is poor. You can't "overkill" based on a theory, and by "practical situations", you actually mean "real-world applications". It's ridiculous to write posts which might make some people believe that sampling above the Nyquist Rate is irrelevant (i.e. "overkill").

I understood nctnico's post so that he's saying that, while in general anything over Nyquist-Shannon doesn't provide any benefit, some provisions have to be made for signals above the rated analog BW beccause the true BW might be higher and because of the filter properties which isn't infinite steep. And that is absolutely correct, and a sample rate in excess of what's required to cover that frequency range is, indeed, "overkill" (or do you want to say a 20GSa/s sample rate would make sense for a 100MHz scope?).

On a side note, I have to say nctnico's English is absolutely fine and much better than what I've seen from many 'native' speakers, and on a personal note I find your (repeated) rather condescending attitude towards non-native English speakers pretty poor. Especially when your own grasp of the use of words hasn't been exactly stellar.
 

Offline eeguy

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Re: Gw Instek GDS2204E (200MHz 4 channel DSO) review
« Reply #62 on: September 17, 2016, 01:23:27 pm »
I did some testing with the GDS2204E and aliasing is minimal because it has anti-aliasing filters in place. With a 200MHz bandwidth the 500Ms/s is more than enough to show the signal. You have to keep in mind that in theory the minimum sampling frequency is twice the bandwidth. Everything more is overkill but in practical situations you need some margin for the anti-aliasing filters.

Thanks. Do you mean it should be OK but if I could get an oscilloscope (100MHz-200MHz) with 1GS/s per channel, that would be better?
 

Offline marmad

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Re: Gw Instek GDS2204E (200MHz 4 channel DSO) review
« Reply #63 on: September 17, 2016, 01:36:40 pm »
I understood nctnico's post...or do you want to say a 20GSa/s sample rate would make sense for a 100MHz scope?

I understood his post, and although you may accept at face value that "with a 200MHz bandwidth, the 500Ms/s is more than enough to show the signal" on a low-cost DSO, I'm a little more skeptical. In any case, there have been repeated discussions here (and much talk by Dave during some of his reviews) on this subject, and whether or not you feel that a sampling rate that is 2.5x the bandwidth is "overkill" to reliably reconstruct complex, high-frequency signals with sin(x)/x, I don't. In that regard, I feel it's worth debating whether it's the correct term in this context for prospective GW-Instek (or any DSO) buyers.

Quote
...or do you want to say a 20GSa/s sample rate would make sense for a 100MHz scope?

You believe there's an equivalency between a sampling rate 2.5x higher than the BW and one that's 200x higher than the BW?

Quote
...and on a personal note I find your (repeated) rather condescending attitude towards non-native English speakers pretty poor.

On a personal note, I find your use of the word "condescending" to describe any other poster on this blog rather humorous, and while I'll fully admit that I'm sometimes (either intentionally or unintentionally) condescending, somehow I doubt you'll follow suit.

And I've certainly never claimed my English is "stellar", and I know I've made plenty of incorrect or awkward word choices while dashing off posts. And yes, nctnico's English is normally fine and I was being overly harsh, but I believe "overkill" to be a misleading description in this particular example.
« Last Edit: September 17, 2016, 02:47:49 pm by marmad »
 

Offline jjoonathan

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Re: Gw Instek GDS2204E (200MHz 4 channel DSO) review
« Reply #64 on: September 17, 2016, 06:13:18 pm »
I don't think it reflects negatively on peoples' English skills, but I do think that many of the remarks in this thread -- "rolloff is not infinitely steep" and "some margin for the anti-alias filters" understate the role of rolloff.

It's typical for modern scopes to devote half (or more!) of their Nyquist band to rolloff rather than sticker bandwidth (i.e. samp rate >= 4x BW). Gentle rolloffs make for better step responses, so Oscilloscope designers prefer them when possible, but the tradeoff is that a huge part of your Nyquist band must then be dedicated to rolloff in order to promise decent attenuation of aliases. Not 10% or 20% of your Nyquist band, 50% or 60% of your Nyquist band, and even then the alias attenuation isn't spectacular. For the front end on my personal scope, a Rigol DS4014 hacked to 500MHz (see "Rigol MSO4024-500" line on the graph below), here is the relationship between sample rate and the alias attenuation they can promise given the gentle rolloff of their front end filter:

SampleRateAliasAttenuation
2BW-0.5dB (!)
2.5BW-2dB (!)
4BW-13dB (actual sample rate, 4 channels)
8BW~30dB (actual sample rate, 2 channels)

I am quite pleased they did not try to sample at 2.5*BW. The benefit of going from 4*BW to 8*BW sampling (-13dB aliases to -30dB aliases) is more debatable, but -13dB attenuation isn't actually all that great -- it's still 20% of the original voltage amplitude, which is a considerable amount of worst case waveform fuzziness. It's comforting to have the option to bump up to 8*BW sampling (aliases at most ~3% of original amplitude).

With credit to Altemir:


Of course, we are discussing the GDS2204E, not the Rigol DS4000 series, but I could not find frequency response plots for the GDS2204E so it would be difficult to comment on the tradeoffs made by GW Instek. Here is the Bode plot for the DS1054Z (credit to ankerwolf) which might be more representative:
« Last Edit: September 17, 2016, 06:16:06 pm by jjoonathan »
 
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Online nctnicoTopic starter

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Re: Gw Instek GDS2204E (200MHz 4 channel DSO) review
« Reply #65 on: September 17, 2016, 06:40:21 pm »
When it comes to aliasing you also have to realise that the roll-off mirrors at half the sampling frequency so higher frequency signals past the Nyquist frequency still get attenuated as if the response continued.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline jjoonathan

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Re: Gw Instek GDS2204E (200MHz 4 channel DSO) review
« Reply #66 on: September 17, 2016, 06:54:50 pm »
True, I should have made it more clear that the numbers I gave were the worst case, where you have a signal just above the Nyquist frequency aliasing to just below the Nyquist frequency. It's an edge case to be sure, but like many edge cases it punches above its weight. It pops up right at the theoretical limit of what a scope can measure, and given that bandwidth costs money and both oscilloscope bandwidths and clock/data frequencies gravitate towards "nice" round numbers, it's an edge case that I could see someone hitting if they weren't careful.
 

Online nctnicoTopic starter

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Re: Gw Instek GDS2204E (200MHz 4 channel DSO) review
« Reply #67 on: September 18, 2016, 11:02:02 pm »
Since there are no other graphs available I measured the bandwidth of my GDS2204E starting at 10MHz with 1 channel enabled at 1Gs/s. I noticed that switching to a more sensitive range changed the amplitude more than I expected so I measured twice using a 0dBm signal and a -20dBm signal and plotted the results in a graph (Y-axis in dB, X-axis in MHz):


The 50mV/div graph shows the -3dB frequency is around 290MHz but for 10mV/div the -3dB point is around 210MHz.
« Last Edit: September 18, 2016, 11:07:10 pm by nctnico »
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 
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Offline Merlot1970

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Re: Gw Instek GDS2204E (200MHz 4 channel DSO) review
« Reply #68 on: September 19, 2016, 07:22:49 pm »
I unboxed my new GDS-2204E yesterday and fired it up..  About 15 minutes into using it, I was able to find a problem on a circuit I"ve been working on..It appeared on screen to be a high impedance power supply causing a glitch at the starting point of my circuit.  My Tek analog scope did not see this, but the Instek picked up the glitch immediately.  I'll see If i can post a photo.


First photo is the captured glitch...When the circuit initially conducts current, it wigs out.

Second photo is the corrected problem.

« Last Edit: September 20, 2016, 03:53:32 am by Merlot1970 »
 
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Offline saturation

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Re: Gw Instek GDS2204E (200MHz 4 channel DSO) review
« Reply #69 on: September 19, 2016, 09:24:56 pm »
Good to hear, would be interested in why the Tek couldn't pick it up and what the Instek had that found it quickly.

I unboxed my new GDS-2204E yesterday and fired it up..  About 15 minutes into using it, I was able to find a problem on a circuit I"ve been working on..It appeared on screen to be a high impedance power supply causing a glitch at the starting point of my circuit.  My Tek analog scope did not see this, but the Instek picked up the glitch immediately.  I'll see If i can post a photo.


Best Wishes,

 Saturation
 

Offline Merlot1970

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Re: Gw Instek GDS2204E (200MHz 4 channel DSO) review
« Reply #70 on: September 20, 2016, 03:54:56 am »
Photos posted, Saturation.
 
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Online nctnicoTopic starter

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Re: Gw Instek GDS2204E (200MHz 4 channel DSO) review
« Reply #71 on: November 14, 2016, 07:31:41 pm »
Just wanted to show a useful application of the input filtering. In a project I'm currently working on I need to do some digital signal processing. Usually I have a PWM output + an RC filter as a monitor output instead of a real DAC. With the GDS2204E the PWM output suffices when combined with the input filtering:

Original signal:


Filtered signal:


Other purposes can be looking at what is output from PWM motor drives and class D amplifiers.
« Last Edit: November 14, 2016, 07:34:01 pm by nctnico »
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 
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Online nctnicoTopic starter

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Re: Gw Instek GDS2204E (200MHz 4 channel DSO) review
« Reply #72 on: December 13, 2016, 06:28:21 pm »
Recently firmware version 1.26 has been released. This version now has band filtering besides low and and highpass input filtering which is an excellent addition  :-+
I also did some testing with UART and CAN decoding regarding the baudrate tolerance because earlier firmware versions where quite strict. From my tests it seems the UART decoding allows a deviation from the baudrate of +/-3%. The CAN bitrate can now be set freely. Also the bitrate tolerance of the CAN decoding exceeds +/-2%.
« Last Edit: December 13, 2016, 06:36:40 pm by nctnico »
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 
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Offline saturation

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Re: Gw Instek GDS2204E (200MHz 4 channel DSO) review
« Reply #73 on: December 14, 2016, 11:14:51 am »
Yes, it seems when they update one model they update the others.  Good to know since there are no announcements from Instek.  ???
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 Saturation
 

Offline JanJansen

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Re: Gw Instek GDS2204E (200MHz 4 channel DSO) review
« Reply #74 on: December 14, 2016, 03:26:52 pm »
If you mess with the fan do you loose the warranty ?
aliexpress parachute
 


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