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Gw Instek GDS2204E (200MHz 4 channel DSO) review
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CC555:
Thx for your reply,

there is a new firmware version, v 1.34


--- Quote ---Version 1.34
1.Added a new ¡§Frequency Response Analyzer¡¨ APP function which can be downloaded from our website.
(This APP only available for MSO-2000EA & MDO-2000E series)
2.Updated the Japanese menu tree translations for SA function.
3.Updated the Japanese menu tree translations for digital filter function.
4.Updated the simplified Chinese menu tree translations for some functions.
5.Updated the Russian menu tree translations for DMM function.
6.Fixed the EVENT table display and storage error issue for UART bus decoding.
7.Fixed the window zoom display issue for I2C bus decoding.
8.Fixed the I2C bus decoding error.
9.Fixed the type of executable for DEMO function.
10.Fixed the return value of SA:MEMory SCPI command.
11.Fixed the return value of :D<x>:MEMory and :DIGital:MEMory SCPI command.
12.Fixed the setting value of TRIG:DEL:LEV SCPI command.
13.The digital filter function can be implemented now after the SEGMENT data caught.
14.The firmware upgrade procedure is now ONLY support the ¡§Safe mode¡¨ firmware upgrading from this firmware version.


--- End quote ---
nctnico:
It seems the biggest change is the network analysis feature for the models which have an internal waveform generator. Unfortunately GW Instek didn't fix the oversampling needed for UART decoding  :-\
DougM:
How well does this 'scope handle input overdrive?

The reason I'm asking is that I quite often want to look at a smallish voltage range of a larger signal. Right now, I've found that my Rigol DS1054Z is truly dreadful in this respect. For example, I have a square wave at 1kHz between 0v and 40V. The Rigol becomes useless at 2v/div let alone at higher gain... (I have some screenshots on the DS1054Z thread). 

Some people may suggest that this isn't a "proper" use of a digital scope, and that I should be keeping the whole signal on the screen and digitally zooming. I, respectfully disagree, and think the input stages should be capable of placing the limited digital resolution on the interesting part of the voltage range. (Especially with only 8 bits of ADC)

That being said, how does the GDS2204E perform in this respect?  I have excellent scopes available at work, but for home use, I think I need something better than the Rigol...

Best regards,
Doug
nctnico:
I did a test with a 20Vpp 1kHz square wave:



The offset range is specified in the datasheet. At 500mV/div this seems to be +/- 25V. At more sensitive settings (200mV/div and less) the offset range is +/-5V.
2N3055:
For DS1000Z:

Offset Range (Probe ratio is 1X)

1 mV/div to 499 mV/div: ±2 V
500 mV/div to 10 V/div: ±100 V

As far as I could see, DougM wants to look at part of 40V P-P signal at better than 1V/DIV or less..
No digital scope I know of will have dynamic reserve of 200x of full screen sensitivity... And probably only +-8 to 10 DIVS...

If A/D converter full scale input for instance is 2V, so on 100mV/DIV  input, your scope  full dynamic range is +- 5 DIVS.  DC offset will be only helpful if you have 100 mV AC riding on top of 12V offset, so you dial in offset in opposite direction to "pull it back" to screen.. Or you AC couple it..
If you have 40 V AC P-P, you need 40V dynamic range signal path for it all to fit in. Without mentioning amplification.. That is with unity gain.

I don't know of any digital scope that can do it. If someone know one I would like to learn about it. It would be good info.
Also, no matter how quick they recover from overload, it ain't pretty...

I believe David Hess mentioned sampling scopes (old analog diode bridge types) in other thread.
Diode bridge sampling scope are direct sampling devices. They don't have input amplifiers and are basically S/H circuit that is disconnected from input all the time, except at the very short time of sample window (aperture). By choosing time at which to sample and if needed adding DC offset, you can look at any part of waveform with no problem of overshoot.
They are repetitive sample devices (random or sequential) and are useful only for repetitive and stable signals..

Modern approach to more detail on digital scopes is hi res scopes (more than 8 bit), keeping signal within dynamic range, and zoom in in software.. 12bit scope will have 4x more detail (pixels) in vertical than 8 bit... But, it costs money...

Regards
Sinisa
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