what an oscilloscope recommended for a woman passionate about electronics?

[CharlotteSwiss]

You only need to connect to one plug (mono) . your arrows are right

I connected the cable to the output of the mp3 player, pressed Auto on the oscilloscope, no signal on the display (if I decrease div volts ok I see many sinusoids, but I also see those without audio cable ..)
I guess I'm wrong ...

[rstofer]

in practice with ac coupling we have the square wave that goes from about -1.5v to about + 1.5v (like a sine wave)
Don't ask me what this ac coupling representation means, I don't know

There is a ton of math involved with the Fast Fourier Transform of a square wave - we'll skip that...  When you start playing with the FFT feature of your scope, you will see a spike at 0 Hz if there is some DC present in the waveform.  When AC coupled, that spike will disappear because there is no average DC voltage.

A symmetric square wave of, say, 0 to 3.3V has an average DC value of 1.65V.  When we display the waveform with DC coupling, all of the signal is above 0V.  However, if we display it with AC coupling, the DC value is removed and the waveform shifts down relative to the 0V reference.

I just did that experiment (DC spike) on my Rigol and sure enough the leading edge of the FFT changes depending on DC vs AC coupling and whether or not there is an average DC voltage.

That's really all there is to it.  Of course, the idea applies to any kind of signal.  We don't usually think about the average DC value of a square wave whose value is always above 0V but it is there nevertheless.  In audio circuits, a great deal of effort is expended trying to remove the DC components.

[alsetalokin4017]

You aren't going to see much of interest in Normal or Auto sweep modes if you just play music into the scope channel. Since music is a dynamic, always changing signal, that is what the scope will show you, and it won't make much sense. You can use Single Shot sweep mode to capture a... single shot );   a snapshot if you will, of the instantaneous music signal and that will be interpretable, if you know how to interpret it! 
(There is a difference between simply using the Auto sweep mode, and what the AUTO setup button will give you....  Please don't confuse these two usages of the word "auto" in your scoposcopy      )

It would be better, in my opinion, to play some constant signals, that is, signals with constant amplitude and frequency. Such as square, sine, triangle ramp, etc. which can be gotten from any number of computer or cellphone signal generator applications. Vary pitch, vary duty cycle, vary amplitude in the generator application and watch what that does to the signal on the oscilloscope.

It is by using the X-Y mode of the oscilloscope that you can get extremely interesting things from real-time sound or musical input.




But that's a more advanced topic for later...

[rstofer]

You only need to connect to one plug (mono) . your arrows are right

I connected the cable to the output of the mp3 player, pressed Auto on the oscilloscope, no signal on the display (if I decrease div volts ok I see many sinusoids, but I also see those without audio cable ..)
I guess I'm wrong ...

Again, we get back to earth ground referenced signals.  The sleeve of the audio plug is at earth ground potential as  is the scope ground clip.  It's only a formality to connect the ground clip to the sleeve (you get a cleaner signal).  So, for this iteration, you can just probe the tip or ring of the connector and ignore the ground connections.  In fact, remove the ground clip on the probe and just probe the 3 connections and see what you get.

About 1/3 the way down is an image of the plug indentifying the tip-ring-sleeve connections.

You might find some tone generator software for your PC and this would output a single tone of known frequency.  Set it for 1 kHz and set your time base for 500 us/div so that a single sine wave takes 2 divisions.

Here is one for Windows 10
https://www.microsoft.com/en-us/p/tone-generator/9wzdncrdhjqn

There are MANY others...

It would be a good source of sine waves.  Change the frequency and see how you need to change time/division.  Get used to doing the inversion (time = 1 / frequency) in your head.  I'm not sure what the 30 Hz thing means but I know if I change it to 50 or 60, it quits working.


There's a Frequency Generator App at the Microsoft store as well.  It generates sine, square, sawtooth and triangle waveforms.

[CharlotteSwiss]

There is a ton of math involved with the Fast Fourier Transform of a square wave - we'll skip that...  When you start playing with the FFT feature of your scope, you will see a spike at 0 Hz if there is some DC present in the waveform.  When AC coupled, that spike will disappear because there is no average DC voltage.

A symmetric square wave of, say, 0 to 3.3V has an average DC value of 1.65V.  When we display the waveform with DC coupling, all of the signal is above 0V.  However, if we display it with AC coupling, the DC value is removed and the waveform shifts down relative to the 0V reference.

I just did that experiment (DC spike) on my Rigol and sure enough the leading edge of the FFT changes depending on DC vs AC coupling and whether or not there is an average DC voltage.

That's really all there is to it.  Of course, the idea applies to any kind of signal.  We don't usually think about the average DC value of a square wave whose value is always above 0V but it is there nevertheless.  In audio circuits, a great deal of effort is expended trying to remove the DC components.

certainly the DC component of the signal obviously has no frequency; I can only imagine that the engineers of audio devices have their work to have a clean current that sounds good.
On the oscilloscope display we see the amplitude of the signal vertically, the time base horizontally .. but the signal frequency is not represented! Maybe we see the frequency in FFT?
thank you   

in the meantime I started learning what the various knobs are for and what they do (trigger not included for now ..) 

[CharlotteSwiss]

(There is a difference between simply using the Auto sweep mode, and what the AUTO setup button will give you....  Please don't confuse these two usages of the word "auto" in your scoposcopy      )

It would be better, in my opinion, to play some constant signals, that is, signals with constant amplitude and frequency. Such as square, sine, triangle ramp, etc. which can be gotten from any number of computer or cellphone signal generator applications. Vary pitch, vary duty cycle, vary amplitude in the generator application and watch what that does to the signal on the oscilloscope.

I did not understand the joke about AUTO, sorry 

sure, I would like to play with constant signals, but at the moment I don't know where to place the probes .. (on cards to be repaired at the moment I don't put the probes, I have to learn first).
So can I get a sinusoidal signal from my pc or mobile phone? but then how do I transmit it to the oscilloscope?
It would be fun to learn about the various signal types!
thank you 

[CharlotteSwiss]

There are MANY others...

this is not installed, it is online, it seems good...

https://www.szynalski.com/tone-generator/

but then the signal I measure it with the oscilloscope on the jack cable of the audio output of the pc?
then I have to try ..

[rstofer]

certainly the DC component of the signal obviously has no frequency; I can only imagine that the engineers of audio devices have their work to have a clean current that sounds good.

Yes, the DC would cause a speaker cone to displace by the average value.  That's why you see so many series capacitors in audio circuits - to block the DC value

On the oscilloscope display we see the amplitude of the signal vertically, the time base horizontally .. but the signal frequency is not represented! Maybe we see the frequency in FFT?
thank you   

You do time to frequency conversions in your head (or with a calculator).  There is also a frequency counter in the scope but I don't know how well it works on composite signals built on sine waves.  It can count square waves and that's my primary interest.

The FFT display will give you some idea of the frequency content and there will be a text display of the frequency/division.  My compensation signal shows a lot of even harmonics.  They should be there!  There are no even harmonics in a square wave.  Hm...

I would have to read the manual to discover what the vertical values represent.  The text display is in extra midget font, I have to use my OptoVisor to read the screen.  Blue on black may be hard to see but red on black is invisible to me.  Color vision problem...

That said, the Siglent FFT is supposed to be a lot better than Rigol's.  I haven't seen examples but I haven't been looking for them.

in the meantime I started learning what the various knobs are for and what they do (trigger not included for now ..) 

Look at your compensation signal at 1us/div.  Now you will see some kind of exponential rise in the rising edge and you can shift the trace back and forth by adjusting the trigger level.  My trace breaks up when I try to get below 300 mV for the trigger point.  You will be able to see exactly where the scope triggers on that edge.

[rstofer]

There are MANY others...

this is not installed, it is online, it seems good...

https://www.szynalski.com/tone-generator/

but then the signal I measure it with the oscilloscope on the jack cable of the audio output of the pc?
then I have to try ..

It is far better to probe the signal using a patch cord.  In fact, I would cut the plug off of the probe end of the patch cord and cut the individual wires to different lengths (to avoid the possibility of shorting the wires.  Then I would tin the ends and use my probe as intended.  It's not always easy to get a probe to stay on the plug.  The ground clip probably isn't necessary and should be removed.

[CharlotteSwiss]

Look at your compensation signal at 1us/div.  Now you will see some kind of exponential rise in the rising edge and you can shift the trace back and forth by adjusting the trigger level.  My trace breaks up when I try to get below 300 mV for the trigger point.  You will be able to see exactly where the scope triggers on that edge.

after dinner I try to see, let's see if I understand ...
 

[CharlotteSwiss]

It is far better to probe the signal using a patch cord.  In fact, I would cut the plug off of the probe end of the patch cord and cut the individual wires to different lengths (to avoid the possibility of shorting the wires.  Then I would tin the ends and use my probe as intended.  It's not always easy to get a probe to stay on the plug.  The ground clip probably isn't necessary and should be removed.

I tried, but I see a confused signal ... I guess there is also noise from the economic audio sockets of a PC ...
I would have expected a song sine wave ... like the icons of the rooms here in the forum ... instead it was a sign of coming and going ..
I guess I have to find something real to measure to see beautiful single signals (like the square compensation wave)
the time will come for these signs to speak to me and I can understand them
 

[rstofer]

I don't know how to use the Siglent but on the Rigol, I would set Trigger Mode to Single and then push the Single button to get a single snapshot of a complex wave.  Make sure the Trigger Level triangle on the right edge of the screen is within the range of the signal.

To get out of Single mode, select Auto mode and press the Run/Stop button. Pages 15 & 16 of your User Manual or search for Single.  More on page 39

In my opinion, Single Mode is the most important feature of the DSO.  Learn how to use it!

[alsetalokin4017]

Here once again we have the opportunity to point out that the AUTO setup button is a different thing than the Auto Sweep Mode.

The AUTO setup button causes the scope to make a "best guess" at the signal and chooses the timebase, trigger level and vertical amplitude based on this guess. It sets the scope up  "automatically" but this may not always be what the user needs to see. It can be a good starting point for probing a completely unknown signal but should not be relied upon to give the user the best data or image possible.

The Auto horizontal sweep mode tells the scope to pause unless a signal over the trigger level is detected, at which point the scope runs and displays the signal. When the signal is removed or drops below the trigger level, the scope stops running and displays a static (still picture) of the last waveform detected. The Normal horizontal sweep mode tells the scope to just keep running, no matter what the trigger level is. If the signal amplitude drops below the trigger level, the trace will just lose horizontal stability but will continue to display, and when the signal is gone you'll see a flat line. The Single Shot horizontal sweep mode (not a trigger mode!) waits for a signal amplitude greater than the trigger level and then runs One Sweep, that is one horizontal screen width, and then stops, holding the display of the waveform detected during that single horizontal sweep.

It is important at this stage to be practicing reading the actual values of traces and their frequencies using the graticule markers. The vertical scale is calibrated in volts per division and the horizontal scale is calibrated in seconds per division -- the scale factors set by the user on the vertical scale and horizontal timebase controls. So if you have vertical scale set to 1 volt per division and you see a signal that is three and a half divisions tall, you are looking at a 3.5 volt difference between the low and high. If you have the horizontal timebase set to 500 microseconds per division and your sine wave is exactly 4 divisions from peak to peak, you have a frequency of 1 cycle per 2 milliseconds or 500 Hz.  ( 1 / 0.002 = 500 ) Und so weiter. 

[CharlotteSwiss]

Look at your compensation signal at 1us/div.  Now you will see some kind of exponential rise in the rising edge and you can shift the trace back and forth by adjusting the trigger level.  My trace breaks up when I try to get below 300 mV for the trigger point.  You will be able to see exactly where the scope triggers on that edge.

ok I set the time base to 1us (with such fast times the angle of the signal is rounded a lot).
But then I didn't understand where I should move the pointer trigger. Down until it comes out of the signal?



sorry but it's not easy for me 

[alsetalokin4017]

The trigger point is where the Blue and Yellow markers intersect. Move the Yellow marker up into the "curvy" part of the signal and watch what happens.

[CharlotteSwiss]

I don't know how to use the Siglent but on the Rigol, I would set Trigger Mode to Single and then push the Single button to get a single snapshot of a complex wave.  Make sure the Trigger Level triangle on the right edge of the screen is within the range of the signal.

To get out of Single mode, select Auto mode and press the Run/Stop button. Pages 15 & 16 of your User Manual or search for Single.  More on page 39

In my opinion, Single Mode is the most important feature of the DSO.  Learn how to use it!

well, now with the single button you think, it is as if you took a picture and you see the single signal .. it seems to me that then continuing to press single shows the next snapshot and so on.
I measured the tip of the audio cable, while online I set the sine wave at a few Hz frequency. For me the important thing is to start understanding the keys, the tigger point, etc.

[alsetalokin4017]

Note that you have almost exactly 9 and a half horizontal divisions between the peaks of that rough "sine" wave. At 20 nanoseconds per division -- what is the frequency of that sine?

[CharlotteSwiss]

The trigger point is where the Blue and Yellow markers intersect. Move the Yellow marker up into the "curvy" part of the signal and watch what happens.

yes I know that the trigger point is the intersection of the two pointers. If I raise the trigger level, I see the vertical signal moving to the left ... to keep the trigger point in the wave. This is the high limit with a still stable signal (trigger a 3,05V)



as soon as I raise the trigger again, here's what happens (+0,01v)



what can all this teach me?

thanks 

note for siglent: already a few times that when I press Print everything stops, I have to remove the plug from the power supply and restart
 

[alsetalokin4017]

Hopefully it teaches you that the Autoset feature does not always tell you what you want to know! Sometimes it can be very misleading, in fact!

(here I am talking about the "sine wave" image above....)

[tautech]

what can all this teach me ?

Triggering to get a stable signal is the most important tool you have ! 

[alsetalokin4017]

If you are having trouble saving screenshots, you could try a different USB thumbdrive. I presume you have tried simply waiting --

The Rigol sometimes is balky in this same way, especially  if a complex display is in use. But using a low capacity thumb drive and a lot of patience cures it for me.

[tautech]

I don't know how to use the Siglent but on the Rigol, I would set Trigger Mode to Single and then push the Single button to get a single snapshot of a complex wave.  Make sure the Trigger Level triangle on the right edge of the screen is within the range of the signal.

To get out of Single mode, select Auto mode and press the Run/Stop button. Pages 15 & 16 of your User Manual or search for Single.  More on page 39

In my opinion, Single Mode is the most important feature of the DSO.  Learn how to use it!

well, now with the single button you think, it is as if you took a picture and you see the single signal .. it seems to me that then continuing to press single shows the next snapshot and so on.
I measured the tip of the audio cable, while online I set the sine wave at a few Hz frequency. For me the important thing is to start understanding the keys, the tigger point, etc.

For audio work we use a much slower timebase setting usually unless we want to see distortion of a very clean sinewave.

[CharlotteSwiss]

Note that you have almost exactly 9 and a half horizontal divisions between the peaks of that rough "sine" wave. At 20 nanoseconds per division -- what is the frequency of that sine?

4Hz the frequency (https://www.szynalski.com/tone-generator/)
in my opinion this signal leaves the time it finds, in the sense that even without starting that online signal, the audio output of the pc connected to the probe shows confused signals on the display ...

[alsetalokin4017]

well, now with the single button you think, it is as if you took a picture and you see the single signal .. it seems to me that then continuing to press single shows the next snapshot and so on.
I measured the tip of the audio cable, while online I set the sine wave at a few Hz frequency. For me the important thing is to start understanding the keys, the tigger point, etc.

(Attachment Link)

You set your sine wave at "a few Hz frequency" but the scope's automatic measurement is indicating 412.858 kiloHertz, and the rough calculation from the graticule markers and the 20 ns/div horizontal timebase setting is wildly different even from that.

This does not indicate anything wrong with the scope... rather it is an artefact of the Autoset function which is guessing what you want to see, and is zeroing in on the noise on top of your true "a few Hz" frequency, rather than the sine wave you are sending it, I think.

[alsetalokin4017]

Note that you have almost exactly 9 and a half horizontal divisions between the peaks of that rough "sine" wave. At 20 nanoseconds per division -- what is the frequency of that sine?

4Hz the frequency (https://www.szynalski.com/tone-generator/)
in my opinion this signal leaves the time it finds, in the sense that even without starting that online signal, the audio output of the pc connected to the probe shows confused signals on the display ...

You miss my point. I am asking you  to _calculate_ the frequency of the displayed sine wave, based on the graticule markers and the timebase setting. You have one full cycle displayed over 9.5 divisions horizontally, at 20 nanoseconds per division. What is the frequency of the displayed wave?