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Offline Electro Fan

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Re: Is An Oscilloscope Practical
« Reply #50 on: January 05, 2019, 08:28:07 pm »
OK, Roger all that.

I'd be surprised if you don't really, really enjoy using the 1054Z.

Better start reading up on JDS vs FY waveform generators.
https://www.eevblog.com/forum/testgear/suggestion-choosing-an-hobby-signal-generator-(jds6600-fy6800-utg1005a)/msg1785575/#msg1785575

This will be somewhat like the Rigol vs Siglent discussions.  There are some other very long threads on the various FY and JDS generator versions.  For somewhere around or less than $100 one of these is likely to be your most economical solution, but I'm betting you will want a waveform generator shortly after the scope arrives.  The Siglent and Rigol waveform generators are nicer than FY/JDS but I think you can probably save some $ and be happy with the FY or JDS.  On the other hand if you have been trained in the DuPont/Fluke school of buy once cry once then you might want a Siglent waveform generator - they are an excellent value.  And if you don't already have one pretty soon you will have to search the threads for a variable power supply.  Unlike entry level scopes where the battle has largely been settled in the EEV forums, power supply choices are pretty large; many makes and models to choose from.  :)  Enjoy the journey.   :-+


After re-reading your original post I should have noticed that you already have many meters.  And DuPont is of course a very seriously capable company.  So given that you repaired equipment there you probably are up to speed on Ohm's Law and can read schematics, which would probably indicate you are pretty familiar with the workings of discrete components including resistors, capacitors, and inductors, and maybe transistors?  And various ICs?

Yes, you are correct in stating I have many types of electrical meters ............… and, while I'm not trying to boast, I've always purchased quality meters such as Fluke, Simpson, Biddle, etc. One reason for this was because DuPont always taught it was best to use and trust only in quality instruments and the other reason is sadly my inclination to feel I always need the best ……………. or at least better than the everyday "norm". This does come at an increased cost for me, but my meters/equipment choices have always served me well.

And you are also correct in stating that I am familiar with Ohm's law, print reading and such. Years ago, I completed a 2 year study in Industrial Electricity and for a while was an electrician with my employer (DuPont). My last 20 years with my employer was actually spent in the Technical organization as a resource for the plant's testing lab. In this position, I not only ensured the instrumentation was on aim, I was also a resource for the electrical shop which maintained the 24 hour support for equipment failures or off-aim conditions. I also worked closely with plant electrical engineers on equipment upgrades and was basically a "wrench" when it was time to tear out the old components and install the new. Therefore, this task, along with my everyday activities gave me ample experience troubleshooting, reading prints, etc. I'm far from an electronics engineer or advanced electronics student, but I do possess strong electrical skills. So yes, I'm familiar with discrete components, but nowhere near being able to design electronic circuitry.

Anyway, I hope that helps clarify some things for you and possibly others. You did hit the nail on the head when you stated:  "...……. you don't want to invest in a scope unless it gets a reasonable amount of use, which is understandable.

Thanks so much!
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Offline Old Printer

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Re: Is An Oscilloscope Practical
« Reply #51 on: January 06, 2019, 04:06:35 am »
A quick look on eBay shows several used 1054z scopes ranging from mid $200,'s to $325. This is an Improvement from 6-8 months ago where it would be hard to find one used for sale. Buying a new 1054 then selling it a year later is likely to net you 75% of the purchase price and a quick sale. That's a pretty safe market for testing the waters.
 

Offline exe

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Re: Is An Oscilloscope Practical
« Reply #52 on: January 06, 2019, 10:50:10 am »
I have dedicated power supplies, an oscilloscope, a wavegen, a bunch of dmms, a logic analyzer, but most of the time I use analog discovery 2. It's not a high-performance device, but for most purposes it's sufficient. It also save bench real estate and always at hand (read makes me more productive).

Disclaimer: I mostly work with frequencies below 10MHz, often below 1MHz.
 

Offline Fungus

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Re: Is An Oscilloscope Practical
« Reply #53 on: January 06, 2019, 04:37:56 pm »
Yep, the Analog Discovery 2 is a great little learning device.

 

Offline Electro Fan

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Re: Is An Oscilloscope Practical
« Reply #54 on: January 06, 2019, 07:23:53 pm »
+1 for Analog Discovery 2
It is a great learning device with a lot of functions

Good Summary of the features/functions, specs, and some user reviews:
https://store.digilentinc.com/analog-discovery-2-100msps-usb-oscilloscope-logic-analyzer-and-variable-power-supply/?utm_source=google_search&utm_medium=ppc&utm_campaign=AD2_pro_oscilloscope_customers&utm_content=action_2&gclid=EAIaIQobChMIo6q4rOrZ3wIVRp7ACh2EjQR4EAAYASAAEgLfS_D_BwE

By the time you add some accessories (probes, adapters, etc) the price (unless you are a student) is similar to Rigol and Siglent entry scopes.  In return for giving up some bandwidth and sampling you get a lot of tools in one compact device.  The other tradeoff is you get a PC/Mac interface rather than a knob/button interface.

Different horses for different courses but if these tradeoffs trip your trigger it is a wonderfully feature rich learning tool.  If the budget permits a case could possibly be made for an AD2 plus a scope.
 

Offline KL27x

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Re: Is An Oscilloscope Practical
« Reply #55 on: January 07, 2019, 12:33:26 pm »
Quote
you don't want to invest in a scope unless it gets a reasonable amount of use, which is understandable.
In my own situation, the scope is a necessary evil. It gets an "unreasonable" amount of use. But when I need a scope, I need a scope. I think if you needed a scope, you would be the first one to know about it.

 >:D
 

Offline VIO47

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Re: Is An Oscilloscope Practical
« Reply #56 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.
 

Offline Fungus

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Re: Is An Oscilloscope Practical
« Reply #57 on: January 09, 2019, 03:44:28 pm »

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?

It depends on the signal source, the way you connect the probe and the oscilloscope settings.

Three variables about which we have no information.
 

Offline VIO47

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Re: Is An Oscilloscope Practical
« Reply #58 on: January 09, 2019, 03:56:31 pm »
For this test I have used a ST32F103 board, signal was generated by PWM timer, test probes connected directly on the board pins, I have started with "Auto Setup" and then I tried to improve the shape using manual settings as much as I know now but without success. Maybe the STM32 is not able to provide a clean rectangular signal at higher frequencies? I am playing with STM since some time but I didn't have an oscilloscope until now.
 

Offline exe

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Re: Is An Oscilloscope Practical
« Reply #59 on: January 09, 2019, 04:52:32 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.

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.
 

Online tautech

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Re: Is An Oscilloscope Practical
« Reply #60 on: January 09, 2019, 05:04:12 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.
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.
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Some stuff seen @ Siglent HQ cannot be shared.
 

Offline rstofer

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Re: Is An Oscilloscope Practical
« Reply #61 on: January 09, 2019, 05:33:51 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.

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.

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.
 

Offline VIO47

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Re: Is An Oscilloscope Practical
« Reply #62 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. 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?
 

Offline rstofer

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Re: Is An Oscilloscope Practical
« Reply #63 on: January 09, 2019, 07:06:02 pm »
Watch Dave's video:



He talks specifically about your bandwidth issue
 

Online tautech

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Re: Is An Oscilloscope Practical
« Reply #64 on: January 09, 2019, 07:06:30 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.
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).
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?
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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Offline VIO47

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Re: Is An Oscilloscope Practical
« Reply #65 on: January 09, 2019, 07:58:31 pm »
Thank you for the video, very good explanation. I will install the last version of firmware. I have the .png files on my laptop, captured with EasyScope but I get error "504 Gateway Time-out" here on the website when I attach the pictures, they have 750 KB each.
 

Offline tggzzz

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Re: Is An Oscilloscope Practical
« Reply #66 on: January 09, 2019, 08:02:10 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.

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.

The frequency is irrelevant; only the risetime is important.
https://entertaininghacks.wordpress.com/2018/05/08/digital-signal-integrity-and-bandwidth-signals-risetime-is-important-period-is-irrelevant/
There are lies, damned lies, statistics - and ADC/DAC specs.
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Online tautech

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Re: Is An Oscilloscope Practical
« Reply #67 on: January 09, 2019, 08:15:45 pm »
I will install the last version of firmware.
:-+
Quote
I have the .png files on my laptop, captured with EasyScope but I get error "504 Gateway Time-out" here on the website when I attach the pictures, they have 750 KB each.
It's easier to get them onto a USB stick where they are only a few 10's of KB each.
Like I mentioned before, use the blue Print button on the front of the scope to get the display capture.
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Offline VIO47

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Re: Is An Oscilloscope Practical
« Reply #68 on: January 09, 2019, 08:38:51 pm »
The 2 pictures attached, hope it works this time.
 

Offline Electro Fan

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Re: Is An Oscilloscope Practical
« Reply #69 on: January 09, 2019, 10:34:12 pm »
Hi VIO47.  As exe and others have said it is possible that several factors are involved but I am betting that the limitation you are seeing is not your probing technique - rather the limitation is the capability to generate the "rectangular" waveform you were anticipating in the first place.  And as tggzzz points out the underlying factor is rise time.  (This is not to minimize the importance of probe technique including good probe grounding to minimize ringing.  This video by W2AEW is definitely worth watching:
- but the larger issue you are facing is bandwidth and bandwidth’s relationship to rise time.)

I realize you are using a ST32F103 board with a PWM timer but if for example we were to look at the specs on a Siglent SDG2122X waveform generator that produces a 120 MHz maximum output frequency for sine waves we would see that the 2122X produces a maximum 25 MHz square wave, with a 9 ns rise time.  If we were to look at an even more expensive Agilent 33522B waveform generator we would see that it has a 30 MHz maximum bandwidth sine wave and it produces a maximum 30 MHz square wave, with a 8.4 ns rise time.  In general, when you look at the sales literature for waveform generators they consistently emphasize the maximum frequency or bandwidth as being that of the sine wave produced.  Other waveforms such as square waves and pulses will sometimes/generally/often be produced at lower frequencies.  Of course, each make and model of generator employs some techniques that will influence the ability of the generator to create the desired waveforms with integrity – but bandwidth is a fundamental consideration and rise time is related to bandwidth.

The following articles gives formulas showing the relationship between bandwidth (as expressed by frequency) and rise time. 

https://www.edn.com/electronics-blogs/bogatin-s-rules-of-thumb/4424573/Rule-of-Thumb--1--The-bandwidth-of-a-signal-from-its-rise-time

As mentioned, for various reasons the 0.35 "rule of thumb" is a rule of a thumb rather than an absolute. Nonetheless, using the rule of thumb I have attached a copy of a spreadsheet showing simple calculations for several frequencies - this provides a quick glance at the relationship between bandwidth and rise time.  The spreadsheet gives the rise time (Tr) results in nanoseconds (ns) and picoseconds (ps). 

At the top we see that a 20 MHz bandwidth will yield a rise time of about 17.5 ns.  We see that 70 MHz (the clock speed I think on your STM32F103) can potentially yield a rise time of 5.0 ns.  Further down we see a 200 MHz bandwidth will yield a rise time of 1.75 ns, and a 400 MHz bandwidth will yield a rise time of 0.875 ns or 875 ps.

To help describe what you might visualize along these lines, if you were to connect an Agilent 33522B generator (rated to produce a 30 MHz square wave with a 8.4 ns risetime) to a 400 MHz Tektronix 2467B oscilloscope and you set the Agilent to produce a square wave with a frequency of 5 MHz you would get something on the Tek scope that would look reasonably like a square wave.  But if you turned the frequency dial on the Agilent generator upward by the time you reached 30 MHz on the generator you would think the 400 MHz scope was displaying something that looks much more like a sine wave than a square wave.

(Keep in mind that when we measure rise time we are generally looking at the time it takes a rising slope to go from 10% of it's peak amplitude to 90% of it's peak amplitude.)

To help further describe what things might look like at higher speeds we find that 10 GHz could yield a 35 ps rise time.  So while a 200 MHz scope would seem pretty “snappy” (not a technical term) in it’s ability to produce a 1.75 ns rise time if we could see a rising slope at 1.75 ns next to a rising slope at 35 ps we would think the 35 ps waveform is headed almost “straight up” and the 1.75 ns waveform by comparison looks pretty “diagonal”.  Regardless of our ability to put human adjectives on what we see with our eyes, our test equipment can give us measurable results and what we associate with square vs rounded or diagonal is best presented quantifiably as rise time – which is a function of bandwidth.  And in the end our test equipment is kind of like the proverbial chain in which the weakest link (either the bandwidth of the waveform generator or the bandwidth oscilloscope) determines our ability to generate and measure rise time.

One other observation about your observation.  When I first got into studying this stuff I thought a square wave would be an ideal waveform to help keep track of clock timing and to ensure the integrity of data encoding and decoding but as you mentioned your signals are decoding properly even with a "distorted signal” (which I think means a non-rectangular looking signal you are seeing on your scope).  Welcome to the magic of both digital technology in general and of test equipment in particular that lets us both quantifiably measure and visually observe electricity as it is manipulated for various purposes including the ability to represent digital (binary) data riding upon analog (continuously variable) signals.


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.

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.
« Last Edit: January 09, 2019, 10:35:47 pm by Electro Fan »
 

Offline VIO47

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Re: Is An Oscilloscope Practical
« Reply #70 on: January 09, 2019, 11:15:37 pm »
Thank you Electro Fan, definitely I have a lot to learn about using the oscilloscope.
 

Offline Electro Fan

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Re: Is An Oscilloscope Practical
« Reply #71 on: January 10, 2019, 01:04:05 am »
You are doing A-OK  :-+

On your 10X setup have your scope show you the rise time.

Thank you Electro Fan, definitely I have a lot to learn about using the oscilloscope.
 


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