Gw Instek GDS2204E (200MHz 4 channel DSO) review

[nctnico]

GW Instek GDS2204E review and testing

The reason I was looking for an oscilloscope is because I wanted an extra oscilloscope to bring to customers. No way I'm going to bring my Agilent DSO7104 to some factory floor! Especially since my other oscilloscope fell from a table during some tests. My basic requirements are 200MHz-ish, reasonably deep memory, serial protocol decoding (including CAN) and easy to transport.

So time to grab something cheap... I have been looking at other (used) oscilloscopes as well like the Agilent/Keysight DSOX2k or 3k series. I didn't like the R&S and Lecroy offerings because while the oscilloscopes are not terribly expensive you have to pay through the nose to get the serial decoding options. Rohde & Schwarz charges over 3000 euro (ex. VAT!) for UART, CAN, SPI and I2C for their RTM1500 series; Lecroy is slightly cheaper but still in the same ballpark. At least the Agilent/Keysight scopes have the possibility to liberate the options or spend around $800 on an option bundle. Rigol would have be an option too but lack of cheap 4 channel >=200MHz models, decoding only what is on screen (utterly useless!) and slow bug fixes put me off. The same goes even more for Siglent which has been  struggling for two years already to get their SDS2000 series oscilloscopes on the rails and there is still no light at the end of the tunnel.

So the search went on... After looking around on various websites the GW Instek GDS2204E caught my eye. The GDS2204E (which is the top model in the GDS2000E range) is a 4 channel 200MHz oscilloscope which comes standard with I2C, SPI and CAN/LIN decoding, LAN (ethernet), USB, segmented recording for around 1290 euro / $1450 (ex. VAT). Now that looks like a good deal! I am not going to take it apart because Dave already did some teardowns of some GW Instek scopes and I doubt the GDS2204E will be much different (A Xilinx Zync + DRAM board and analog front-end) . Besides that I have it for evaluation and at the first sign of serious problems it goes back! I got my GDS2204E from a local dealer called Eleshop. Oddly enough it got shipped to me from Good Will Instruments Europe directly which turned out to be located in the Netherlands. Unfortunately they did not install the latest firmware on it (V1.20 at the moment of receiving it). Also the calibration certificate is dated from January 2015 so this scope has been in their warehouse for a while! Updating the firmware is described in the firmware update guide but it is not very clear. After the firmware update the scope says it needs to be turned on/off but after that the GW Instek logo remains on the screen. After 15 minutes I decided to power cycle it again and this time it started. Pfew!



During my testing I ran into some issues and GwInstek has send me version 1.21b to test with. The update from 1.20 to 1.21b2 went smoother; the oscilloscope started by itself after a short while. After I found a few more issues they send met version 1.21b6 to test with. In the end this review went through a few rewrites to update it with the fixes.  Also the update manual is not very clear on whether the update procedure must be run twice (update the kernel and then the firmware itself) or not. Better safe than sorry so I loaded each new firmware file twice.

OK! Let's see how the Taiwanese build oscilloscopes...
First impression: lots of function keys around the screen and it also has a 'force trigger' button. Very handy to get some lines on the screen to help adjusting the trigger level. Others complained about the position of the 'Autoset' button. I think I'll have to agree with them because it is very close to the 'run/stop' and 'single' buttons. To add to the insult the 'Default' button is below the 'single' button. The top-right corner is definitely a danger zone for pressing buttons without looking and messing up the settings because there is no undo button. For the rest the layout of the buttons seems pretty standard. Each channel has it's own control but I don't really care whether each channel has it's own controls or you have to select a channel first. BTW most scopes need extra 'virtual channel' buttons to control math and bus (decoding) traces so you you still have channels without dedicated controls. Some rotating knobs are push buttons (channel offset, trigger level, horizontal position). Pushing them makes the control go back to zero. What GwInstek did right was putting a seperate select/enter button next to the rotating knob (called 'variable') for changing values. On other scopes pushing a rotating knob very often results in selecting a different option. On the GDS2204E the rotating knobs respond well and the accelleration is just right for selecting single items or change a large number quickly. Even the on-screen keyboard (which I tend to hate in general) for entering text and numbers is easy to use compared to other on-screen keyboards I have come across!

The GDS2204E also has the ability to choose whether to expand the signal from the trigger point or from the time-base offset. The selection is slightly hidden in the acquisition menu but it is a very handy feature to zoom in on part of a signal quickly without needing to scroll left & right to get the point where you want to look at on screen again. On other oscilloscopes the way to do this is to set the trigger point somewhere along the horizontal axis. On my DSO7104 I can choose between left, centre or right and on my Yokogawa DL1740 I can set it freely.

Another interesting point are the available languages, As far as I can see the scope supports English, Taiwanese, Chinese, Japanese, Korean and Russian. No German, French, Italian or Spanish which would be important to support for the European market since the people in those countries are notoriously bad at speaking other languages than their own!

Test plan
Based on past experiences I have made a test plan with items I wanted to test. I want to take the GDS2204E through it's passes thouroughly to make sure I don't get burned again by an incomplete and bug infested oscilloscope. Tests in random order:
- Bandwidth / aliasing
- Memory length versus number of channels enabled since this wasn't specified very clearly
- Samplerate versus channels enabled (again not specified very clear)
- FFT function
- Filtering
- Protocol decoding and especially how much of the memory is decoded
- Saving images and data
- Saving / recalling setup
- Cursors
- AM modulation signal distortion problem Dave spotted in the GDS2304A
- Operating / using the scope
- PC software
- Networking abilities
- Signal noise floor
- Fan noise level
- Peak detect and roll mode
- Segmented recording and decoding
- Retaining settings
- Storing waveforms
The secondary goal is to use the oscilloscope for a couple of hours in order to spot stability problems.

Memory / Operating / using the scope
The GDS2204E oscilloscope has 10Mpts per channel which isn't shared and not used for double buffering so each channel really has 10Mpts unless FFT is enabled which can be used up to 1Mpts (I have carefully avoided the word limited here because a 1MPts FFT is anything but limited!). The samplerate is 1Gs/s with up to (any!) 2 channels enabled and 500Ms/s with 3 or more channels enabled. The fan produces a low humming sound but it is not extremely loud but there is also a high pitched whining noise coming from it which could become irritating in a quiet environment. The fan noise level is pretty much similar to my Agilent DSO7000 and doesn't become annoying. Each channel has a 1-2-5 selectable probe division factor with a  range from 0.001x to 1000x (nice!) and the channels can be switched between Volts and Amperes. When set to Amperes the division factor also shows Volt per Ampere. There is also a dedicated function key to select the 10x factor directly as this is the most used value. After playing a little with the various functions and buttons it has become clear to me that the firmware is a general purpose one that GW Instek uses among other oscilloscopes. There are greyed out options for digital channels, function generator options, etc and it seems they can also add extra (paid) options to future firmware versions. The protocol decoders for example are listed as software options. Besides the decoders there are also applications for enabling digital filters on channels, data logging and a voltmeter. One neat feature is that this oscilloscope also has internal storage so you aren't required to bring a USB stick along for storing images or some data. The internal storage is 32MB which is enough for lots of screendumps but not for storing serious amounts of waveform data (10MPts results in a 244MB CSV file per trace). When browsing through files it shows a thumbnail of images. The firmware developers obviously had some time to spare on small details like these! When creating a screendump by pressing the hardcopy button the process is remarkably quick. Not some progress bar showing it is doing an image dump for several seconds. The GDS2204E pops up a message with the filename which has been saved almost immediately after pressing the hard copy button.

Another fun fact is that the frequency for the probe calibrator signal output can be adjusted. Perhaps they guessed it can also serve as a simple signal generator.

After the firmware update I ran the self calibration procedure. There is a calibration signal output BNC for this purpose which needs to be connected to an input when the oscilloscope says so. Additionally there is also an SPC (signal path compensation) procedure which can only be run after the scope has been on for at least 30 minutes.

One quirk so far: when in stop mode the oscilloscope goes into acquisition when the 'zoom' button is pressed. WTF? This doesn't happen if you press the 'pause/playback' button so the 'pause/playback' button is the safe route into zoom mode without starting an acquisition. Oddly enough this only happens with acquisition lengths set to 1Mpts or 10Mpts. According to GwInstek this is due to a limit in the hardware but since the 'pause/playback' button sometimes allows to get into zoom mode while staying in stop mode I'm not so sure... For example the workaround doesn't work when decoding is enabled though.

I also tested peak detect in roll mode and the GDS2204E has no problems showing a 16ns pulse in 2s/div so that is good. On the other hand the roll mode scrolls a bit jerky which gets worse with more channels enabled. The response to controls also slows down when it needs to do calculations on long acquisitions.

Screen layout
The screen layout on the 800x480 display isn't too crowded though I wish they went for a 12x8 or 14x8 graticule with squares instead of 10x8 rectangles; it would make better use of the wide screen. There is a dedicated menu-off button to get rid of all the menus so no drama there. What I like is the frequency counter in the bottom right corner which seems to be based on number of edges the trigger sees. It is always handy to have a quick idea about the frequeny of a signal. This frequency counter keeps working while in stop mode.

Retainging settings
I can be short about this: the settings are retained between power cycles. Even the input filtering settings are retained. Let's mark that as OK.

Bandwidth and acquisition modes
I measured the bandwidth for each channel with the reference level at 10MHz (the generator I used doesn't go lower) and using a BNC T with a 50 Ohm terminator to make the inputs 50 Ohm-ish. All channels have an equal bandwidth of 290Mhz but they start to roll-off from 70MHz so it seems the anti-aliasing filter isn't very sharp. OTOH a sharp anti-aliasing filter will cause more phase shift and peaking so pick your poison. When having 3 or more channels enabled (500Ms/s samplerate) the useable bandwidth is 200MHz. Above that frequency there is all kinds of aliasing but that is to be expected. But there is something odd: with peak detect enabled the 20MHz sine wave gets distorted when having 3 channels enabled! There is a 2ns (1/500MHz=2ns) delay between the distortions so perhaps it is trying to display 2 peak values next to each other as one waveform which isn't going to work. Actually I think the peak-detect mode should disable itself at certain time base settings where there are less samples than (horizontal) pixels on the screen!


When in stop mode and expanding a waveform with peak detect on (in the area of 5ms/div) there are aliasing distortions as if it doesn't do peak-detect at all. Are these phenomena to be expected? Yes, it all has to do with limits of sampling systems! GW Instek has send me some screenshots from a Tektronix scope they use and it shows exactly the same behaviour at low time/div settings with peak-detect enabled. When doing similar tests on my Agilent DSO7104 it also shows similar behaviour but to a lesser extend. I guess at some point a trade-off between screen update speed and going through all the memory has to be made.

Noise level
The minimum volts per division setting is 1mV and with the inputs open the noise is around 0.5mV (using a 50 Ohm terminator makes no difference). When a channel is set to GND the ADC value is clearly overwritten by 0.

[nctnico]

Decoding
As I wrote earlier the GDS2204E can decode UART, CAN, SPI and I2C. First I tried some CAN decoding for which a samplerate of 4 times the bitrate seems to be enough for the decoding to work properly. The decoding works as expected and the GDS2204E does decode the entire memory which can take a little bit of time when the memory length is set to 10Mpts. I think at memory lengths over 1Mpts it is necessary to do the decoding in hardware instead of using the generic CPU in the oscilloscope in order to keep the response snappy. Still it is 1000 times better to do decoding slow than not at all! Because everything is decoded you can stop the acquisition and scroll through the messages and enlarge signal sections where there is a problem with the partial message still on screen so you know where you are. The decoding also works in zoom mode. Excellent! A nice touch is that the decoded information (bus trace) can be moved along the vertical axis with the variable button. I also tested triggering on certain CAN messages based on the ID and that also works as it should be. The same goes for I2C decoding. It is even possible to trigger on certain (multi-byte!) data patterns in the I2C stream with per-bit wild cards. Suddenly I had to debug an SPI problem so instead of the DSO7104 I pulled out the GDS2204E and found SPI decoding works as it should be. There is one catch though: SPI decoding must have a chip select signal! For fun I also looked at the UART decoding and tested how much oversampling is required. It turned out a 38400bps stream needed at least 500ks/s to decode properly (that is 13 times). There is also a packet mode in the UART decoding which concatenates characters into a packet. The end of a packet can be 0x00, CR, LF, space or 0xff. Similar to the I2C triggering the UART triggering can be based on up to ten bytes so it is easy to trigger on specific messages which works as advertised. But unlike the other protocols the UART decoding can also show the messages in ASCII (readable text) and it is also possible to setup the trigger using ASCII. Take notes Rigol & Siglent! However I did find a problem with the packet mode decoding; at some time/div settings the text is placed at the wrong location on the screen. Also the packet mode decoding disables viewing the event table. I'm a bit dissapointed by this because having messages in an event table would make it easy to go through a conversation between 2 devices because every message is on a single line.

Persistence
Persistence can be adjusted from a 16ms to 4s in doubling steps, set to infinite or disabled. In the initial firmware this didn't work properly so I reported this back to GwInstek and they fixed it in the V1.21b6 update!

Cursors
The cursors work slightly different than the oscilloscopes I'm used to. There are two modes: one with only horizontal controls where the vertical values track the selected input and one with seperate horizontal and vertical cursors. Selection between modes (off, horizontal, both) happens by pressing the cursors button repeatedly. There is an on-screen display which shows the values of the cursors. The units can be selected between seconds, Hz, percentage and phase. Additionally to showing the delta between the cursors the dV/dt is also shown so it is easy to see the slew rate of a signal. Unfortunately the cursors cannot be placed outside the screen. In zoom mode the cursors can be used outside the screen but their positions don't track the signals exactly as if the resolution of the cursors is somehow limited so it is not possible to enhance the horizontal cursor resolution much by using the zoom mode. IMHO GwInstek should fix this!

Averaging and high-res
The GDS2204E does not have a high resolution mode but it does have averaging and/or the input filtering to clean up noisy signals. A side note: high-res mode is tricky to use because oversampling a signal while producing a meaningful result requires having enough Gaussian distributed noise and the ADCs to be very linear. On my Tektronix TDS500/700 series scopes I could get the weirdest high-res results with the bandwidth limiting on. My primary use for high resolution and averaging are to clean a signal up to allow for more accurate cursor measurements because of the (much) thinner trace. More about input filtering later on. Unfortunately averaging is only available for 10kpts to 1Mpts memory lengths and together with zoom mode averaging seems to be limited to 100kpts max.

Automated measurements
Ofcourse the automated measurements are there. The gating (which data is used) can be choosen between entire record length, screen or between cursors. Statistics can also be enabled so all in all it is pretty complete.

Input filtering
The input filtering can be selected between low pass or high pass filtering. When enabled the waveform capture rate slows down visibly with long record lengths so the input filtering is obviously a post-processing step performed in software. Still the filtering is very useful to clean a signal up. For example: if a signal has a lot of high frequency components or 50/60Hz hum then the filters can be used to get rid of it. The filters can be adjusted in steps of 1 Hz from 1Hz to 500MHz. Band-pass filtering would have been nice as well but maybe I'm pushing my luck here. On other scopes I use high-resolution mainly to clean up noisy signals in order to make accurate cursor measurements but the input filtering can be used as a much more precise tool for this purpose. And the cool thing is that since input filtering is a post processing function you can change the filter settings in stop mode so you can apply different filter settings to a signal without recapturing it.

FFT
FFT is under the menu which pops up by pressing the math button but FFT is seperated from the other math functions. The FFT works OK and it is easy to adjust. The long (up to 1Mpts memory for FFT) allows to get a fine grained FFT result. It is not a problem to look at an FM modulated signal with a 20MHz carrier and a 100kHz frequency swing. It would have been nice if there was an averaging mode on the FFT signal to stabilise it a bit more but that is a very uncommon feature. So far I have seen this only on the Tektronix TDS500/700 series. To be honest the speed at which the FFT is calculated is pretty quick. I think (part of) the FFT is accellerated in hardware; it certainly feels it is doing 1Mpts FFT faster than my Agilent DSO7000 is doing 128kpts FFT.

Math
There are two math functions. The first is a simple one with +. -. * and / operators while the second one is a complex math function which allows to create a trace based on a math expression. GW Instek has taken this part quite seriously because there are quite a lot of possibilities here to create complex math expressions. I have not ventured deeply into this feature but it looks useful to take on more demanding signal analysis tasks. To start an expression can use data from the traces, reference memory or 2 variables. Besides the usual operators  (+, -, *, /, >, <, etc) the trigoniometric functions (sin, cos, tan, etc), integrator, differentiator and the automatic measurement functions are at your disposal. The two variables I mentioned earlier can be changed from the menu by using the variable knob.

LAN (ethernet) connection and software
The GDS2204E comes standard with an ethernet connection so let's see how useful it is. After enabling DHCP the oscilloscope obtains an IP address immediately. First of all I tried the Openwave software. As usual this doesn't work; it produces a 'can't find device' message or is this only supposed to work with USB? How 2001... The software does not have an installer and looks pretty basic. Just a few buttons in a screen. Perhaps it can be used to do some screen captures??? Actually I didn't expect anything else because remote control software is often just a checkbox item for this kind of equipment (keep some software engineering intern busy for a while between getting coffee for everyone). So lets forget about the Openwave software. The oscilloscope also doesn't have a built in webserver/website. This would have been nice to do quick screen captures and/or offer a platform independent remote control. In 2016 you should be able to control your scope from your smartphone! Then again the build-in webserver in my Agilent DSO7000 would be just as useful if/when Agilent left it out.

In the ethernet settings menu there is also an option to enable a socket server. If I enable it I can telnet to the oscilloscope and it responds to the "*IDN?" SCPI command to query a SCPI compliant device for it's name and other information so I guess this is an SCPI over ethernet interface. I have not tested it further but it could prove useful for automated testing. Through the applications (APP) button it is also possible to mount to a network share. Interesting! But.. what kind of network share? The manual doesn't tell! Trying a Windows networking share works first time and mounting/unmounting a disk for the second time also works (with a Linux server so it if doesn't work with Windows blame uncle Bill!). I managed to save screendumps and a dump from a waveform (a 244MB CSV file for 10Mpts) to the network drive without problems and it is not slow either. Unfortunately a USB stick is no longer recognised after mounting/unmounting a network share. I had to power cycle the scope to get the USB stick back to work again. After some more fiddling it turned out I stumbled onto a very specific sequence involving removing the USB stick and mounting the remote drive which goes wrong. Please no remarks about fools and their ability to break stuff which is supposed to be unbreakable. This is also reported back to GwInstek.

Signal distortion?
Dave shows us a GDS2203A in 'EEVblog #474 - GW Instek GDS-2000A Series Oscilloscope Unboxing & First Impression' ( ) from May 2013. With Dave's AM modulated signal he managed to get all kinds of weird signals on the screen (from 45:00) so I tried the same on the GDS2204E and guess what!? I managed to reproduce them (10MHz carrier + 10kHz 95% AM modulation)!  I informed the dealer that this is a bug I can't live with; in turn they informed GwInstek and a couple of days later (despite it being Christmas time!) GwInstek produced a new version (1.21b2) which fixed this problem. So extra points for Gw Instek for being able to resolve firmware issues quickly!

Segmented recording
I also tested segmented recording. This works as you would expect. There is also the possibility to calculate statistics over a range of recorded segments based on an automatic measurement. My primary interest however was bus decoding combined with segmented recording and see how this would work. Bus decoding combined with segmented recording is an ideal way to debug intermittent failures in communication between devices over a long time period. As expected the bus decoding works when stepping through the segments. However it is not possible to display an event table from all the segments in segmented recording mode. The event table only shows events from the current segment. That is a bit of a let down because a full event table would allow to store all the decoded data in one file for analysis on a PC. It is much easier to go through a lot of data on a PC than on an oscilloscope.

Reference traces
Last but not least I played a bit with the reference traces. Up to 4 reference traces can be stored. These come in handy every now and then to compare an old (reference) trace with a new acquisition or to have various acquisitions on the screen simultaneously. In the GDS2204E the reference traces only work up to 1Mpts because they are stored in flash memory and therefore can be recalled after a power cycle (this is common behaviour for many oscilloscopes). The time/date, length and samplerate of the reference trace can also be recalled. Because the reference trace is written into flash memory it takes a while (5 seconds or so) before a 1Mpts reference trace is saved though. Storing 10Mpts probably was too slow because I can't imagine the flash is too limited to store 40MB of data for 4 reference traces. What is very useful is that the reference traces can be moved and scaled both horizontally and vertically. I don't recall seeing that before on any oscilloscope I have used so far; both my Agilent DSO7000 and Yokogawa DL1740 can't do that. Additionally the reference traces can also be saved to a waveform file, read from a waveform file and/or used for math/FFT functions. All in all the reference traces allow to use the oscilloscope for doing (re)analysis on the data later on. However the protocol decoding and signal filtering can't use the reference traces as a source but I'm already very happy with the possibilities the reference traces offer.

Bugs / short comings
A short recap on the bugs / short comings I have found:
- signal distortion with peak-detect on at 100ns/div or less and with 3 or more channels enabled.
- cursors don't track the signal in zoom mode accurately
- zoom mode has some limits regarding memory length and switching between zoom-mode and normal mode so you have to decide whether you want to use zoom mode before doing a single-shot acquisition.
- Whining noise from PSU

Conclusion
I think the GDS2204E is a very good deal for an oscilloscope in this price class especially since everything works as advertised and it offers a very complete package with lots of clever solutions. The oscilloscope is also very straightforward and easy to use; I did not need the manual at all. The GDS2204E also has a lot of areas where the firmware engineers went the extra mile. Take the dedicated x10 probe function key for example, the possibility to move the bus decoding trace vertically or to be able to use the reference traces for more than just a marker on the screen. A lot of the operations are performed (mainly) in software but it is not particulary slow. I like the fact GwIstek didn't choose to limit functions so everything works snappy but instead they went for getting the maximum functionality from the hardware even if it means the user has to wait a little while in some cases. In the end you want a tool which gets the job done!

Anyone considering buying a Rigol, Siglent, Hameg (R&S) or other economy oscilloscope should really REALLY look at GwInstek's offerings first as it seems that GwInstek has a good grip on their software and offers good value for money! I'm surprised Rigol and Siglent have so much traction on this forum; GW Instek is almost like a hidden gem. With my software engineering hat on I have the impression the engineers at GwInstek started with realistic goals for the firmware so it could be completed and tested within a reasonable timeframe. Better have 9 functions implemented correctly than 10 functions being buggy/incomplete! I'll admit there where some bugs in the firmware when I got it initially so firmware testing could be better but it seems GwInstek is able to come up with fixes quickly once they know what is wrong. They send me 2 updates in a 4 week timeframe. I also think the GwInstek GDS2204E gives the lower bandwidth Keysight DSOX2k and DSO3k series a run for their money due to the much larger memory and standard decoding options. For example a serious downside of Keysight's scopes in general is that in a common usage scenario their memory is only one quarter of what is specified due to the memory being shared between channels and cut in half again by double buffering. Worse: according to the DSOX2k user manual the memory gets even shorter when reference traces are turned on. You never really know what kind of memory depth your Keysight scope is actually using. The GDS2204E on the other hand is very open about this and has enough memory under the hood to store a minimum of two 10Mpts segments. When debugging a serial bus problem you really want as much memory (segments) as possible. I'm wondering if/when GwInstek comes up with a version of the GDS2000E series with digital channels.

Now the main question is: do I keep it? The answer is yes (due to the V1.21b6 firmware!). I have tested it thouroughly and some of my comments are close to nit-picking because my other (A-brand!) oscilloscopes turn out to be just as bad. Also this oscilloscope packs a few clever features which will come in handy for certain measurements. Two thumbs up! 

Note: I had to cut the posting in two parts because appearantly the limit for one posting is 20000 characters. No, I did not type all of this just now; this posting has been written during the past 6 weeks.

[wraper]

Anyone considering buying a Rigol, Siglent, Hameg (R&S) or other economy oscilloscope should really REALLY look at GwInstek's offerings first as it seems that GwInstek has a good grip on their software and offers good value for money! I'm surprised Rigol and Siglent have so much traction on this forum; GW Instek is almost like a hidden gem.

Thanks for the detailed review. I had GW Instek scope in the past and used their another equipment at my previous job. Now I own 3 Rigol devices and certainly I don't quiet get all that worshiping on them. They certainly have some issues including the build/design quality. Those GW Instek devices certainly felt better. Nice to read that someone finally made a good review on a modern device from them.

[wblock]

That is an excellent review!  It is really encouraging to hear that they have fixed bugs that quickly, and the shared codebase means more than one model benefits from the fixes.

Is the "VPO" (DPO) what did not work initially but was fixed by one of the firmware updates?

My Instek power supply has PWM fan speed control, but it is choppy enough to make the fan noise very noticeable.  There is a Microchip app note on reducing that: http://ww1.microchip.com/downloads/en/AppNotes/00771b.pdf.

[markone]

Decoding
-snip
There is one catch though: SPI decoding must have a chip select signal!

This means that the two channels scopes in this family are not able to decode an SPI interface even in the monodirectional form (DATA LINE + DATA CLK), could you please confirm this ?

Another question : looking at the Dave's video of GDS2000A @50:00 we can see that there is no screen intensity gradient applied for AM waveforms on the screen, is also the case for your instrument (so 2000E family )?

IF negative, could you post a screen that shows intensity gradient capabilities ?   

Anyway, you are doing a great debugging job for them !

[wraper]

Another question : looking at the Dave's video of GDS2000A @50:00 we can see that there is no screen intensity gradient applied for AM waveforms on the screen, is also the case for your instrument (so 2000E family )?

What I've seen on the GDS2000A video does not go along with what Dave commented. IMO probably he just set the the persistence from min to max very quickly, so it was hard to see that actually it is there. And most of the time it just was set to max.
In that moment (48:22) he just set the persistence from max to min in about 1.5 seconds and said there is none.

[markone]

What I've seen on the GDS2000A video does not go along with what Dave commented. IMO probably just set the the persistence from min to max very quickly, so it was hard to see that actually it is there. And most of the time it just was set to max.
In that moment (48:22) he just set the persistence from max to min in about 1.5 seconds an said there is none.

I'm not familiar with GW settings for persistence and intensity gradient but if you go to 50:00 the AM modulated signal appers to be like a "solid block" without any gradient, dunno if due to erroneous settings.

So i'm wondering if it's a different matter for the series 2000E, as it seems to be for the 1000B looking at the the Dave's @37:10.

[wraper]

I'm not familiar with GW settings for persistence and intensity gradient but if you go to 50:00 the AM modulated signal appers to be like a "solid block" without any gradient, dunno if due to erroneous settings.

Because persistance was set to 100%, at least at that 48:22 moment he was adjusting it from 100% down to the bottom. If you set it to 100% on rigol, it will be the same. Probably on Instek default setting is 100% (I don't have one to verify). On Rigol DS2000A which I have, the default intensity setting is 50%.

[nctnico]

Decoding
-snip
There is one catch though: SPI decoding must have a chip select signal!

This means that the two channels scopes in this family are not able to decode an SPI interface even in the monodirectional form (DATA LINE + DATA CLK), could you please confirm this ?

Another question : looking at the Dave's video of GDS2000A @50:00 we can see that there is no screen intensity gradient applied for AM waveforms on the screen, is also the case for your instrument (so 2000E family )?

IF negative, could you post a screen that shows intensity gradient capabilities ?   

Anyway, you are doing a great debugging job for them !

According to the manual SPI decoding won't work on 2 channel versions. There is intensity grading but it starts from 50% intensity and then goes up. This means it doesn't simulate an analog scope but has the practical purpose of showing a signal very clear when there is a signal. IMHO this is a good thing; I don't want a scope which shows signals in a way they are hardly noticeable. I have used my fair share of analog scopes and one of the problems I ran into repeatedly was dim (hardly visible) signals.

Regarding the debugging: I would have liked to avoid that but since they came up with a fix so quickly it was impossible to say 'too little, too late' 
I didn't got a message from the dealer indicating when Gw Instek is going to release a new official version but I guess that will be after the Chinese new year.

[markone]

There is intensity grading but it starts from 50% intensity and then goes up. This means it doesn't simulate an analog scope but has the practical purpose of showing a signal very clear when there is a signal. IMHO this is a good thing; I don't want a scope which shows signals in a way they are hardly noticeable. I have used my fair share of analog scopes and one of the problems I ran into repeatedly was dim (hardly visible) signals.

Many thanks, now it's clear how it works.

As far as i understood you owned a Siglent SDS2000, in which areas do you think that this one is much better ?

[Hydrawerk]

Thanks for the review.

[nctnico]

There is intensity grading but it starts from 50% intensity and then goes up. This means it doesn't simulate an analog scope but has the practical purpose of showing a signal very clear when there is a signal. IMHO this is a good thing; I don't want a scope which shows signals in a way they are hardly noticeable. I have used my fair share of analog scopes and one of the problems I ran into repeatedly was dim (hardly visible) signals.

Many thanks, now it's clear how it works.

As far as i understood you owned a Siglent SDS2000, in which areas do you think that this one is much better ?

First of all: the GDS2204E has mature firmware which works and the SDS2000 doesn't so there isn't really any sensible comparison to make 
But I'll try.... Compared to the SDS2000 the GDS2204E is cheaper, has an impressive amount of processing power under the hood, has way more FFT points (1 million versus 1000), decodes the entire memory, can average much longer traces, has input filtering, more extensive math functions, saves images as PNG (instead of uncompressed BMP), decoding is included and more extensive protocol triggering to name a few.

[markone]

First of all: the GDS2204E has mature firmware which works and the SDS2000 doesn't so there isn't really any sensible comparison to make 
But I'll try.... Compared to the SDS2000 the GDS2204E is cheaper, has an impressive amount of processing power under the hood, has way more FFT points (1 million versus 1000), decodes the entire memory, can average much longer traces, has input filtering, more extensive math functions, saves images as PNG (instead of uncompressed BMP), decoding is included and more extensive protocol triggering to name a few.

Well, lot of important points, ie " decodes the entire memory" and 1M FFT's point will be important for me, i will be tempted to buy the 100Mhz 2 channels version but things like not shielded & whining PSU and overall not so great build quality worry me a bit.

Many thanks for your prompt answer.

[wraper]

Well, lot of important points, ie " decodes the entire memory" and 1M FFT's point will be important for me, i will be tempted to buy the 100Mhz 2 channels version but things like not shielded & whining PSU and overall not so great build quality worry me a bit.

I'd prefer non shielded Instek over siglent rust. Also, from what I have read, it seem to use quasi-resonant SMPS topology, so the need for the shielding should be significantly reduced.

[markone]

I'd prefer non shielded Instek over siglent rust. Also, from what I have read, it seem to use quasi-resonant SMPS topology, so the need for the shielding should be significantly reduced.

Watching to Dave's 1000B teardown video @31:25   you can see some quite strange periodic noise stuff, i'm wondering if it comes from PSU, that seems to be identical to the one mounted on GDS2000E family.

Regardless of the switching PSU's topology you always have high dV/dT circuit traces, avoid shieldind is not an option without implications, also for safety reason.

If some capacitor blows out, with open frames solution like that the whole instrument is involved.

[nctnico]

I'd prefer non shielded Instek over siglent rust. Also, from what I have read, it seem to use quasi-resonant SMPS topology, so the need for the shielding should be significantly reduced.

Watching to Dave's 1000B teardown video @31:25   you can see some quite strange periodic noise stuff, i'm wondering if it comes from PSU, that seems to be identical to the one mounted on GDS2000E family.

Regardless of the switching PSU's topology you always have high dV/dT circuit traces, avoid shieldind is not an option without implications, also for safety reason.

If some capacitor blows out, with open frames solution like that the whole instrument is involved.

It's not like every capacitor explodes at some point (especially since they have safety vents). Also the input circuitry is well shielded in a metal box so there really is no noise visible from the PSU with the inputs open on my GDS2204E. It is hard to tell where the artifacts Dave shows come from. First of all there are signal display issues in the firmware of the scope Dave is showing and secondly he noticed the circuitry is slightly different so that could also be a source of noise coupling into it. Furthermore it seems Dave never has opened a Tektronix TDS500/600/700 series scope; in those scopes Tektronix has also used ribbon cable to distribute the power (a lot!) to various parts of the scope. For as long as you stay within the maximum voltage and current rating of a connector it is fine to use whatever connector to distribute power.

@Achmed99: I think the letter E is for Economy.

[markone]

It's not like every capacitor explodes at some point (especially since they have safety vents). Also the input circuitry is well shielded in a metal box so there really is no noise visible from the PSU with the inputs open on my GDS2204E. It is hard to tell where the artifacts Dave shows come from.

Yes, sure, luckily not all capacitor explodes at some point but ...just in case.

Times ago it happened to me that a brand new Panasonic fax machine had a PSU capacitor suddenly failed spreading electrolyte liquid through the vents everywhere inside the box, ruining everything it touched, quite toxic smell inside the room !.

Of course it was swapped under warranty.

So you can confirm that your scope is not affected from the same strange noise that Dave spotted in its review ?
And, just out of curiosity, have you bought your from TME ?

[nctnico]

I have no weird noise on my scope. I have attached some screendumps with the inputs open and set to 1mV/div at various time/div settings. Acquisition mode is set to sample and the variable persistence set to 240ms. But note that I have (newer) beta firmware in my scope!

[tequipment]

E is the economy version but really its  just a new scope version.  In some ways it has better specs.

Also it had a 20% price drop yesterday on our site www.tequipment.net

Thanks
Evan Cirelli

TEquipment.NET

[nctnico]

It seems the beta firmware got finalised into version 1.24 which was released a couple of days ago together with a new feature (seperate download) which shows the FFT result and the traces in a seperate window. I have not had the time to see if there are more new features in this firmware release.

I did however made a slight modification to the fan. It started resonating into the casing which made an annoying sound. Instead of going for a new fan I choose to change the mounting using rubber universal fan mounts: http://uk.farnell.com/duratool/dtrfmm-1/fan-mount-universal-4-5mm-pk50/dp/2472730 These soft rubber mounts decouple the fan from the casing so that inbalances in the fan do no get amplified by the casing.




I used the remaining pieces of the fan mounts to create stand-offs for the other 2 holes of the fan to keep it a bit more in place. The end result is a much quieter scope. And the best part is that I have 48 of these fan mounts left for other projects/equipment!

[markone]

I did however made a slight modification to the fan. It started resonating into the casing which made an annoying sound. Instead of going for a new fan ... -snip

Those ADDA fan are cr@p, i changed mine with an 60x60x15 Sunon Maglev (MB60151V3-000U-A99), much less noise and much more air flow, actually internal scope's case temp dropped a lot.

The original 20mm deep fan falls to close to analog front-end metal shielding and does not work properly, the resulting air flow is much lower than spec sheet, the 15mm model has instead enough room to work good. 

[nctnico]

The Sunon fan you choose is rated at 25dB where the original Adda fan is rated at 18.4dB which translates into the Sunon fan being 4 times louder but I guess the Sunon fan also moves a lot more air. I'm sorry but I don't see how the Sunon fan can be more quiet than the Adda fan when you just compare the fans as they are by themselves. Mounting the original Adda fan with the rubber mounts has lowered the fan noise a lot! All in all I don't think the original Adda fan is a bad choice perse if you look at the specs but it is not a high quality fan and any unbalance can easely couple/resonate into the casing. I did look at fan replacements but the good & low noise fans from Papst etc start from 25 euro (ex. VAT) and there is not a large improvement where it comes to noise: 16dB versus 18.4dB.

[markone]

The Sunon fan you choose is rated at 25dB where the original Adda fan is rated at 18.4dB

I worked a lot with fans for forced air cooling systems in power electronic and i soon learned that the last thing that you can trust is the noise rating on spec sheet, especially if you compare them among different brands.

In addition if the application implies high static load / flow, when air "sounds" through metal fins and holes, those numbers become utterly useless.

In this scope it's even worst, the fan placement is wrong for a 20mm deep device, as you can check in your scope the intake side falls about 9mm from the nearby metal shielding that literally suffucate it, you can forget the promised CFM and the alleged dBA, flow is much lower than expected and noise is much higher.

The 15mm model has additional 5mm air space in between that let it work a lot better, no sh!t.

Now facts are that if i put my hand in proximity of scope's fan exhaust grid i feel a much stronger air flow than before and i have LOT LESS NOISE 

Back side bnc connectors now are almost at Tamb while before were about 15 °C higher, also case top in proximity of Zynq chip is now colder.

I would say it's a huge improvement, especially because this room temp can easily exceed 30 °C in summer time (34 °C in 2015 !) and there is still room to further decrease fan speed (and noise) with a series resistor.

Sunon MB60151V3-000U-A99 comes for cheap (1/3 papst cost), has right size for the purpose, much less bearing noise and no vibrations at all.

[nctnico]

Hmm now I'm tempted to give that Sunon fan a try and compare... where did you buy it?

[markone]

Hmm now I'm tempted to give that Sunon fan a try and compare... where did you buy it?

From TME http://www.tme.eu/en/details/mb60151v3-a99/dc12v-fans/sunon/mb60151v3-000u-a99/ but now it's no more available, i think you can only order the slower model (i fear too weak) ha60151v4, available for cheap also from Reichelt.

My suggestion is to go for the V3 model than adjust rotation speed with a series resistor and avoid normal sleeve and ball bearing fans, are much more noisier.

Of course shipping cost does not justify an order only for one fan.