Electronics > Beginners

Is An Oscilloscope Practical

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tautech:

--- Quote from: VIO47 on January 09, 2019, 03:36:38 pm ---Hi EEVblog Users,

I just registered on this forum and this is my first posting here. Hope this topic is the right place for my question, I don't think I should open a new topic only for a question.
I am a hobbyist in electronics and about one month ago I bought an oscilloscope SDS1202x-e. It is my first one and I hope it was a good choice, until now it helped me a lot. I did not intend to spend too much money only for hobby activities and I like very much the SPI and I2C decoding abilities included for free.
One question I have now, hope somebody can clarify here; the user manual is only summary and I couldn't find too much information. I have noted that the oscilloscope is able to show a correct rectangular signal shape up to about 2 MHz, at 4 MHz the shape is no more rectangular, the corners gets rounded, at much higher frequencies it shows more like sinus signal. Is this normal? Since the oscilloscope can go up to 200 MHz, I have seen a test at 250 MHz too, sinus signal of course, I was thinking it should work correctly with rectangular signal at frequencies higher than 2 MHz, at least the SPI frequencies. Anyway, on SPI the decoding works very well even with that distorted signal.

--- End quote ---
Welcome to the forum.

As with all DSO waveform reconstruction issues, please ensure the firmware is the latest version, V1.3.23. (SDS1202X-E)
Link: https://www.siglenteu.com/download/6573/

Next, signal source, probing technique and/or input type has everything to do with the fidelity of square waves.
See this thread for examples, good and bad and advice on suitable connection methods.
https://www.eevblog.com/forum/testgear/show-us-your-square-wave/

Particularly the signal source quality, as frequency increases the risetime of the leading edge becomes more difficult to remain as 'ideal' or perfect. Even when slow, for digital comms it won't matter if all edges have the same risetime.

rstofer:

--- Quote from: exe on January 09, 2019, 04:52:32 pm ---
--- Quote from: VIO47 on January 09, 2019, 03:36:38 pm --- I have seen a test at 250 MHz too, sinus signal of course, I was thinking it should work correctly with rectangular signal at frequencies higher than 2 MHz, at least the SPI frequencies. Anyway, on SPI the decoding works very well even with that distorted signal.

--- End quote ---

Be sure that 1) signal source can really produce square wave of that frequency 2) you have 10x probes 3) proper probe compensation 4) proper probing techniques.

--- End quote ---

Make sure you have set the probes to 10x and have the channel configured for 10x.  You should get pretty decent waveforms out to about 25 MHz (figuring 9th harmonic is still in the -3 dB bandwidth).  The waveform may still be acceptable out to 50 MHz if the -3dB point is around 250 MHz.

VIO47:
Thank you all for the replies. I have checked the probes compensation and adjusted it first time when I received the oscilloscope. Regarding the source, indeed it may not be the best one, so I think I should trust more the oscilloscope and less the micro controller. Switching the probe on 10x makes a huge difference, I didn't thought it is so important. I intended to attach 2 pictures but I cannot post back my message with the pictures attached (size is below 2000kB).
Regarding the firmware, it's a bit strange, I have software version 7.1.3.17R1 and this is not listed on Siglent website. Or maybe the version I have is 1.3.17R1 (without leading 7) and then V1.3.23. is a newer one?

rstofer:
Watch Dave's video:



He talks specifically about your bandwidth issue

tautech:

--- Quote from: VIO47 on January 09, 2019, 06:47:52 pm ---Thank you all for the replies. I have checked the probes compensation and adjusted it first time when I received the oscilloscope. Regarding the source, indeed it may not be the best one, so I think I should trust more the oscilloscope and less the micro controller. Switching the probe on 10x makes a huge difference, I didn't thought it is so important.
--- End quote ---
It's due to a far less capacitive loading of the circuit when using 10x probe setting.


--- Quote --- I intended to attach 2 pictures but I cannot post back my message with the pictures attached (size is below 2000kB).
--- End quote ---
For screenshots use the blue Print button to save a png file to a USB stick.


--- Quote ---Regarding the firmware, it's a bit strange, I have software version 7.1.3.17R1 and this is not listed on Siglent website. Or maybe the version I have is 1.3.17R1 (without leading 7) and then V1.3.23. is a newer one?
--- End quote ---
Yes, install V23 at your earliest convenience, it offers many improvements to the UI.
View the release notes here:
https://www.siglenteu.com/wp-content/uploads/dlm_uploads/2018/09/SDS1000X-E_Release_Notes.pdf

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