what an oscilloscope recommended for a woman passionate about electronics?

[CharlotteSwiss]

  External Trigger is like having an extra channel that you can synch to but you can't display.

sure, but in practice the only usefulness of this extra ext channel is to be able to introduce a signal to triggering the trigger.
reading some documents online, they claim that by doing so the signals measured by the analog channels are not passed into the trigger circuits, and this could contribute to having more stable signals (especially those with small amplitudes)

I could actually have several scopes all synched to an external trigger so they all start the display at the same time.

this idea seems reasonable to me, it could be a good reason to use an external signal for many identical triggers on different devices

As I said earlier, AC Line trigger is useful for probing signals that are synchronized to the mains frequency.  Perhaps a phase shift lamp dimmer or the vertical ramp on an analog television set.  You can play with it, just select AC Line trigger and touch the probe tip with your finger to see the waveform is already stable.  Since you are looking at radiated mains voltage, it is already synched to AC Line.  The display will be stable regardless of the voltage level on the trace.

before asking here, I had already noticed this thing: in fact if I set AC line and probe the signal from my hands (obviously 50Hz) on the display I have a stable signal: this means that the ac line trigger does its job

I think the User Manual does a pretty decent job of explaining the trigger capabilities starting on document page 55 or PDF page 79

i think the manual is ok, but maybe for a novice user many things are poorly explained. Anyway, come on are on page 84 and until now, with some difficulty, I have learned all the features. I still have 150 pages left, but it is also true that then there will be quite simple things that won't take too much time from me (lan connections, pc, save files, etc.)

I'm pretty sure this is wrong but I don't have a 4 channel Siglent.  My DS1054Z 4 channel scope does NOT have an Ext Trigger input.  Of that, I am certain.

in fact maybe they meant two channels.
But the wording in the manual is misleading: even without external triggering, all channels would sample signals...

thanks rstofer
 

[CharlotteSwiss]

I see that however the producers of signal generators, give importance in generating an external trigger signal: I was looking at the Siglent SDG830 series, and I see that they have the external trigger out socket (they don't even cost much, just over a 6900 of which you can read about it ...)
But this will be a thought I will spend time on as soon as I finish the oscilloscope manual..
 

[tautech]

I think the User Manual does a pretty decent job of explaining the trigger capabilities starting on document page 55 or PDF page 79

https://www.siglent.eu/_downloads/51337474

Notice the 2d sentence where Siglent states that 4 channel scopes don't have an Ext Trigger input.  That's pretty common.  Two channel scopes will most always have the input.  Then they turn right around a couple of paragraphs later:

External trigger input:
External trigger source can be used to connect external trigger signal to the EXT TRIG channel when all of the four channels are sampling data.

I'm pretty sure this is wrong but I don't have a 4 channel Siglent. 

Yes it is incorrect for the 1 GSa/s X-E 4ch DSO's however Siglent's 2 GSa/s and 5 GSa/s 4ch DSO's do have Ext trigger in.

Someone was too busy doing Copy/Paste when writing the X-E manual. 

I see that however the producers of signal generators, give importance in generating an external trigger signal: I was looking at the Siglent SDG830 series, and I see that they have the external trigger out socket ........

Very basic AWG but if you don't want to spend much they are OK. We only stock SDG810 as our lower cost AWG and for anything better recommend the 2 ch SDG1032X which are a well featured nice AWG albeit just 14 bit like the SDG800 models.

[rstofer]

The SDG1032X dual channel 30 MHz AWG is only $20 more than the SDG810.  I show it at $319 here in the US, discounted from $399.
https://siglentna.com/product/sdg1032x/

The SDG1032X is far superior for not much more money.  I don't know about pricing in Switzerland.


I bought the SDG2082X-E for no particularly good reason except the part where I wanted to draw a Valentine's Day Heart waveform on my scope to amuse my wife.  I don't work on analog and I certainly don't work at 80 MHz but the unit was overkill for the project so that's what I bought.

Pay attention to the specs (read the manual and ask questions) because although the 2082 is an 80 MHz AWG, the square wave is limited to 25 MHz and the Arbitrary Waveforms are limited to 20 MHz while the ramp is limited to just 1 MHz.  So, yes, it's an 80 MHz AWG, for the sine wave, but the maximum frequency is much lower for everything else.

[tautech]

Ah yes, the Valentines day heart. 

https://www.eevblog.com/forum/chat/a-valentine_s-day-activity-for-your-scope-and-function-generator/

[rstofer]

I see that however the producers of signal generators, give importance in generating an external trigger signal: I was looking at the Siglent SDG830 series, and I see that they have the external trigger out socket (they don't even cost much, just over a 6900 of which you can read about it ...)
But this will be a thought I will spend time on as soon as I finish the oscilloscope manual..
 

I imagine there are some waveforms that are just plain difficult to trigger on.  Maybe modulated sine waves, maybe completely arbitrary waveforms with steps of various voltages.  It might be darn difficult to find the beginning of a thousand point arbitrary waveform.  But the signal generator knows exactly where the waveform starts.

[tautech]

Bursts of any kind can be fun but Charlotte hasn't quite got that far yet.
Knowing how best to apply trigger Holdoff is the key to obtain rock solid triggering without needing an External trigger.

Lessons for later down the road........

[CharlotteSwiss]

Very basic AWG but if you don't want to spend much they are OK. We only stock SDG810 as our lower cost AWG and for anything better recommend the 2 ch SDG1032X which are a well featured nice AWG albeit just 14 bit like the SDG800 models.

as soon as I have finished studying the oscilloscope, I will ask here for the choice of the generator, I will be advised in the best way 

I bought the SDG2082X-E for no particularly good reason except the part where I wanted to draw a Valentine's Day Heart waveform on my scope to amuse my wife.

nice gesture to your wife 

I imagine there are some waveforms that are just plain difficult to trigger on.  Maybe modulated sine waves, maybe completely arbitrary waveforms with steps of various voltages.  It might be darn difficult to find the beginning of a thousand point arbitrary waveform.  But the signal generator knows exactly where the waveform starts.

I believe that with external trigger from the generator, it is possible to make almost any waveform stable

Bursts of any kind can be fun but Charlotte hasn't quite got that far yet.
Knowing how best to apply trigger Holdoff is the key to obtain rock solid triggering without needing an External trigger.

Lessons for later down the road........

the study of the tigger holdoff will arrive in a few pages; but the complicated part was starting a new world ... before taking the siglent I knew nothing about the signals, now I have already learned many new things for me 

[CharlotteSwiss]

Reminder for Siglent engineers: when you push the adjuste knob, it has the bad habit of rotating by changing the setting (it should have been harder to turn) 

the chapter on trigger types was very long, complicated but it taught me a lot by experimenting with the compensation signal
today I can say that I understand a lot of things about the trigger, 50 days ago I didn't even know it existed

In the meantime, I went away quickly in the Serial-Decode chapter (I2C, SPI etc ..) I will experiment if the opportunity should happen ...
100 more pages and I can declare myself promoted 

[rstofer]

Reminder for Siglent engineers: when you push the adjuste knob, it has the bad habit of rotating by changing the setting (it should have been harder to turn) 

The Rigol DS1054Z has a detent-less encoder for option selection.  There is a popular modification to replace it with one having detents.  Desolering is the real risk; damage to the PCB would be terminal for the scope.  So, cut the legs off and desolder them one-by-one then clean out the holes.
I don't know if a similar mod is available for the Siglent nor would I recommend bashing a brand new scope.  The Rigol also needed a quieter fan - another common mod.

the chapter on trigger types was very long, complicated but it taught me a lot by experimenting with the compensation signal
today I can say that I understand a lot of things about the trigger, 50 days ago I didn't even know it existed

Most of the time you will simply trigger off a waveform.  Every once in awhile you will need to go back and review the chapter on Triggers.

In the meantime, I went away quickly in the Serial-Decode chapter (I2C, SPI etc ..) I will experiment if the opportunity should happen ...
100 more pages and I can declare myself promoted 

Back to the Arduino! 

You can generate SPI without having a peripheral.  That is, there is no ACK condition that, if it fails, aborts the transmission.  I2C requires some kind of peripheral.  The good news is that I2C only has 2 signals whereas SPI has 4.  Trigger SPI on SS' and don't display the signal and then display SCK and either MISO or MOSI.

You can do this with just an ordinary Arduino but I really recommend the Freenove Ultimate Starter Kit for the quality of the tutorial:

I don't have the Arduino version of the Starter Kit but I do have, and highly recommend, the Raspberry Pi (4) version.  You can add peripherals to the Pi while using a logic analyzer or either the Analog Discovery or Digital Discovery running on the same machine.  I really like the Pi 4 with the Freenove kit.

https://github.com/Freenove/Freenove_Ultimate_Starter_Kit/blob/master/Tutorial.pdf

https://www.amazon.com/Freenove-Ultimate-Compatible-Programming-Electronics/dp/B08B4D5MV5

The kit uses primarily I2C (SPI isn't used AFAICT) but it is the most difficult of the serial protocols (in my view).  I avoid it at every opportunity (many peripheral chips come as either SPI or I2C, I buy the SPI version).  The SPI interface is also much faster!

[CharlotteSwiss]

thanks rstofer.
The problem of the adjust knob is not serious, I would have preferred it to be harder to rotate, it would have avoided positioning often on wrong values.
Yes maybe Edge will almost always find the trigger point, but still trying the other types of triggers (pulse, window, slope, etc.) helped me a lot to better understand how the trigger works.
(while studying I write the main things I learn about an open office).
The kit costs very little and is interesting, in the future I will certainly enter this world. Now I have to learn the oscilloscope well, then there will be the signal generator.
But it is interesting to think that I can decode serial signals (then if this allows to detect errors I don't know)
 

[rstofer]

For UART serial, coming from a uC before the voltage levels are changed to RS232, the Tx line will idle high.  Connect both probes to Tx or Rx and see which one wiggles when the Arduino sends a char.  You should find Tx on pin 1 and Rx on pin 0 but Tx is what we care about.

Write a little code to send a short string (like "Hello") and trigger on the falling edge of Tx.  With some time/div work and a bit of decoding voodoo, you should see the characters on the screen.  Obviously, this is a single shot trigger.

Your Arduino code to print a simple string just once will look like:

Code: [Select]

void setup()
{
    Serial.begin(9600);
    Serial.write("Hello");
}
void loop()
{
}
[/font]

Setting: 5V/div, 500 us/div, single shot, trigger on falling edge.  Enable serial protocol decoding. Set the scope to ready and press the reset button on the Arduino.  You should see a long trace and the decoded string on the screen.

Something like this:

[CharlotteSwiss]

fantastic, in practice the decoding of the serial signal highlighted the word hello on the display.
Not having Arduino, I can't try, for now I haven't tried any serial signal, I should open some device to connect the probes to some protocol, or my car that has the CAN line
 

[rstofer]

It turns out there is a special trigger for RS232 and it knows better than I how to trigger on the waveform.  I'm sure your user manual will discuss all this in the section on Decoding.

The Rigol only decodes what is on the screen so very long strings won't decode.  If you scrunch up the waveform to capture all of the chars, there won't be room for the text in the decoding waveform.  The scope isn't a logic analyzer, it can't decode "War and Peace" by Tolstoy.  When bringing up a new system, keep the message short.  If the scope gets the proper decode on a few chars, it will get the proper decode on anything.

Which brings me back to I2C.  In the Freenove kit for the Raspberry Pi, there are at least 2 I2C projects:  One for reading an ADC and the other for sending messages to an LCD display.  The LCD message is too long to be any fun capturing and decoding.  The ADC is just 4 bytes (2 to tell the ADC to start and 2 for the ADC to send the result (1 is the command to read while the second is the actual value coming from the ADC).  I recommend starting I2C with a simple peripheral like the ADC even if there isn't one in the Starter Kit.  Or, shorten up the message to the LCD.

Heck, I recommand the Pi 4 and the associated Starter Kit anyway.

[rstofer]

fantastic, in practice the decoding of the serial signal highlighted the word hello on the display.
Not having Arduino, I can't try, for now I haven't tried any serial signal, I should open some device to connect the probes to some protocol, or my car that has the CAN line
 

I wouldn't do that for two reasons:  The available energy in the car battery should something get shorted and, more important, damage to the ECU.

$34 USD for the starter kit with an Arduino work-alike OR just the Arduino for $23 USD doesn't seem like a lot.  Tariffs and customs are unknown to me...

You can get 5 Arduino Nano's for less than $20 USD
https://www.amazon.com/Emakefun-Arduino-Micro-ATmega328P-Micro-Controller/dp/B07GPPK4DK

The Arduino UNO R3 is the standard board for most projects.  The NANO is handy on a solderless prototype board.
https://www.amazon.com/Arduino-A000066-ARDUINO-UNO-R3/dp/B008GRTSV6

You're going to reach a point where you just can't move forward without a way to generate signals and protocols.  It will be sooner than you think!

[CharlotteSwiss]

I joked about the car (I already have a connector for the laptop, where it is possible to analyze / set all the parameters of the car, my father uses it when he does the service)
Of course you need signals, even just studying this siglent, if I had had a signal generator I would have had less difficulty in understanding many functions.
While arduino is a part of electronics that I don't know, but which I would like to study at the time ..
For example, I recently repaired my father's methane detector, I see that it would be possible to reproject it with arduino, or the car's parking sensors, etc.
Goodnight rstofer (at least for me, in your part it's only late afternoon)
 

[CharlotteSwiss]

I arrived at the FFT function, but despite having read some guides, I can't decipher what I see on the display! The manual is obviously based on initial firmware, the menu is almost totally different!
In the attached image it is the usual square wave signal Vpp3v 1Khz I simply did auto set from the menu on page 3/3.
From what I understand FFt shows us the frequency domain on the horizontal axis, while in the vertical axis it is represented by decibels.
But what is not clear to me would be: my signal is 1Khz, why is the graph full from 0Hz up to 50Mhz?
Shouldn't my signal just be represented at 1Khz in the graph?
This FFT confused me ...
 

[rstofer]

Now you're getting into Fourier Transforms - a mathematical representation of arbitrary signals.  The math gets deep - quick!

https://en.wikipedia.org/wiki/Fourier_transform

First the answer:  A square wave with 0 ns risetime is composed of sine waves of the fundamental frequency plus the sum of all the odd harmonics from DC way up to daylight (a really high frequency).  All of the odd harmonics - an infinite number of them.  Each harmonic (spike on graph) is at a decreasing amplitude so, for practical purposes, we might stop calculating at some reasonable frequency where the amplitude is getting pretty close to 0V.

You should see a spike at 1 kHz and then all of the odd harmonics 3 kHz, 5 kHz, 7kHz, etc out as far as the scope can go (or maybe it is limited by a maximum frequency setting).  When looking at a 1 kHz fundamental, it wouldn't make sense to go as far as 1 MHz and certainly not 50 MHz.  That would be the 50,000th harmonic!

You might also have a spike at 0 Hz if there is a DC component - a square wave from 0V to 3.3V.  This has a DC value of 1.65V and we talked about this weeks ago.  If the waveform is symmetric (AC coupled), the 0 Hz spike should disappear.

3blue1brown does a good job in this video

[rstofer]

I arrived at the FFT function, but despite having read some guides, I can't decipher what I see on the display! The manual is obviously based on initial firmware, the menu is almost totally different!
In the attached image it is the usual square wave signal Vpp3v 1Khz I simply did auto set from the menu on page 3/3.
From what I understand FFt shows us the frequency domain on the horizontal axis, while in the vertical axis it is represented by decibels.
But what is not clear to me would be: my signal is 1Khz, why is the graph full from 0Hz up to 50Mhz?
Shouldn't my signal just be represented at 1Khz in the graph?
This FFT confused me ...
 

Specifically, what you are seeing is the spikes at 0V, 1kHz, 3kHz, 5kHz...49999kHz - all of the odd harmonics up to 50 MHz.  You need to stop the upper frequency at around 9 kHz or 11 kHz (the odd 9th and 11th harmonics).

The FFT confuses me as well.  It was a 3rd year subject in undergrad and the reason it comes up so late in the 4 year program is the depth of the math underlying the transform.  The transform itself and the plot of amplitude versus frequency is pretty simple to understand.  Doing the math to dig out the coefficients for the harmonics gets a little more involved.

Around 11 minutes into that video, the author decomposes a signal with an annoying high frequency hum and plots the various spikes.  It is then easy to see which frequency needs to be filtered and he shows the result after filtering out that specific frequency.  This is what the FFT is used for!  What frequencies are present in the signal and which would I like to remove (or amplify).

For the square wave, I gave you the idea that it is composed of all the odd harmonics from DC to daylight.  As the risetime increases, the number of harmonics decreases until the square wave looks like a  sine wave and there is only the fundamental frequency left.

ETA:  When the rise time increases numerically, the edge moves away from vertical.  The rise time value is higher (like 100 ns is greater than 10 ns) but the number of required harmonics is less because the edge is less vertical.  When I wrote "rise time increases", I meant numerically larger or visually slower.

The rise time of the compensation signal on my Rigol is 10 us.  That's pretty slow when you think in terms of a simple 74LS00 quad NAND gate switching in 10 ns.  That gate switches about 1000 times faster than the compensation signal and it isn't even very fast logic.

Rise time is usually measured as the time between the 10% and 90% levels of the rising edge.  There is a fall time spec as well.  Your scope will provide these measurements.

It's going to take more than 1 video to catch what is happening.  Google for 'fft on scope' and see what you can turn up.

[CharlotteSwiss]

Now you're getting into Fourier Transforms - a mathematical representation of arbitrary signals.  The math gets deep - quick!

https://en.wikipedia.org/wiki/Fourier_transform

First the answer:  A square wave with 0 ns risetime is composed of the fundamental frequency plus the sum of all the odd harmonics from DC way up to daylight (a really high frequency).  All of the odd harmonics - an infinite number of them.  Each harmonic (spike on graph) is at a decreasing amplitude so, for practical purposes, we might stop calculating at some reasonable frequency where the amplitude is getting pretty close to 0V.

You should see a spike at 1 kHz and then all of the odd harmonics 3 kHz, 5 kHz, 7kHz, etc out as far as the scope can go (or maybe it is limited by a maximum frequency setting).  When looking at a 1 kHz fundamental, it wouldn't make sense to go as far as 1 MHz and certainly not 50 MHz.  That would be the 50,000th harmonic!

You might also have a spike at 0 Hz if there is a DC component - a square wave from 0V to 3.3V.  This has a DC value of 1.65V and we talked about this weeks ago.  If the waveform is symmetric (AC coupled), the 0 Hz spike should disappear.

I will try to study the link and the video thanks 
I also tried with AC coupling, the initial peak remains it seems to me.
I have seen that by decreasing Hz / div the signal becomes larger.
I find it difficult to understand what the graph shows me going to the right.
In the classic view of the display we have the signal time horizontally, and it is clear. Here we have the frequency, but the frequency of my signal should always be 1Khz and therefore I don't understand what this graph wants to show us in the horizontal direction, as it could possibly indicate an error or disturbance.
I'm missing something I know ..
bye thank you 

IMPORTANT: we wrote together, tomorrow I see your further answer, in the meantime thanks
For me it's time to work at night ;-)

[rstofer]

When we take the FFT of a signal, we are trying to find out what frequencies are present and their amplitude.  The grass at the bottom of the trace is the noise floor.  We usually ignore it.

We want to see the frequency of each significant spike and the amplitude.

Khan Academy (world famous for Saul Khan's mathematics series) also has a series on Electrical Engineering.  Here is a link to the beginning of the Fourier Series topic:

https://www.khanacademy.org/science/electrical-engineering/ee-signals/ee-fourier-series

Here is a link to the beginning of the EE program:

https://www.khanacademy.org/science/electrical-engineering

I'm not trying to push the AWG issue again but the Siglents allow you to create a fundamental sine wave and then add in a number of odd or even harmonics at adjustable amplitudes.  In the Fourier program above, Saul is creating a more-or-less square wave out of the fundamental, 3rd, 5th and 7th harmonics at declining amplitude.  You can see how, with an increasing number of harmonics, the waveform gets more and more 'square'.  You can do this with the Siglent SDG 1032X.  You can pick a fundamental frequency and then keep adding harmonics while watching the waveform on your scope.  Not all AWGs have this capability so make sure you read the datasheets.  That Valentine's Day Heart is a terrific example of using harmonics with appropriate phase and amplitude values to create a really strange waveform.  Note that it really IS a waveform.  It has a beginning and end as well as continuous values over the range.  Mathematically, it would just be considered magic.

And that is how you learn what the FFT, indeed the entire topic of Fourier Analysis, is all about.  We can hand wave and watch videos until the cows come home but the real learning happens on the bench.

This topic of Fourier Analysis is the basis for all signal processing.  It is terribly important but it takes time to come to grips with it.

Khan Academy for math and the EE track at Khan Academy are my two favorite resources.  3blue1brown is also a great resource.  If I were in college, or even high school, I would want to know about desmos.com for graphing and symbolab.com for solving.  Great resources!

[rstofer]

For giggles, I created the attached image which uses a 1 kHz fundamental sine wave at 1Vpp plus 3 kHz at 0.33Vpp plus 5 kHz at 0.2Vpp (voltages aren't the exact coefficients but close enough for a demonstration).

You can see where the sine waves have added together in such a way that they begin to look like a square wave.  This stuff is MAGIC of the highest order!

The FFT is scaled at 2kHz/div so the first spike is at 1 kHz, the next at 3 kHz and finally one at 5 kHz. Note that there is no DC spike, the waveform is symmetric about 0V.  You can see the decreasing amplitude of each harmonic.

[maxcy]

Just go on Ebay and look around for something in your price range. A 100 Mhz, dual channel oscilloscope is pretty standard and will do almost anything will will want to do. Working on TVs, radios, fixing broken test equipment like signal generators, troubleshooting electronics kits, etc.  You will probably want to investigate what a 10x scope probe will do and you will need a good pair to use with your scope.

Since you are very curious about electronics you may want to learn more about the theory that goes with it, not to mention that you can also get involved with math. If you really very smart and want to learn more about the theory of things like circuit design so that you can better understand electronics, then there are tutorials all over the internet. If you really want to learn other things like circuit design, digital logic, etc I'll point you MIT (Massachusetts Institute of Technology), IIT (Indian Institute of Technology) and CIT (California Institute of Technology) as they have a lot of Utube tutorials  on every subject imaginable including electronics on Utube.

[CharlotteSwiss]

Just go on Ebay and look around for something in your price range. A 100 Mhz, dual channel oscilloscope is pretty standard and will do almost anything will will want to do. Working on TVs, radios, fixing broken test equipment like signal generators, troubleshooting electronics kits, etc.  You will probably want to investigate what a 10x scope probe will do and you will need a good pair to use with your scope.

Since you are very curious about electronics you may want to learn more about the theory that goes with it, not to mention that you can also get involved with math. If you really very smart and want to learn more about the theory of things like circuit design so that you can better understand electronics, then there are tutorials all over the internet. If you really want to learn other things like circuit design, digital logic, etc I'll point you MIT (Massachusetts Institute of Technology), IIT (Indian Institute of Technology) and CIT (California Institute of Technology) as they have a lot of Utube tutorials  on every subject imaginable including electronics on Utube.

thanks for the information and the links of the famous universities. 

(Non-relevant note: I have already chosen the oscilloscope)
 

[CharlotteSwiss]

Specifically, what you are seeing is the spikes at 0V, 1kHz, 3kHz, 5kHz...49999kHz - all of the odd harmonics up to 50 MHz.  You need to stop the upper frequency at around 9 kHz or 11 kHz (the odd 9th and 11th harmonics).

already with this note alone, I think I begin to understand what I was missing ...
I will read more about your speech and the next two from about Monday, I think I will understand a lot about FFT.
(we have a lot to work in the ward in this difficult period, so I have little time at home and I can't study .. but no information will be lost)
thanks rstofer, very kind as always