what an oscilloscope recommended for a woman passionate about electronics?

[CharlotteSwiss]

I update for the problem of saving the display images on a USB key in my sds1202: I bought 2 small keys (1GB), but I usually block the oscilloscope.
Now I am trying another method: the manual says to format FAT32, the I want to try to format FAT.
From the first tests it seems not to cause the problem, but I haven't tried many times; I will keep the situation updated!
 

[CharlotteSwiss]

I was playing with the oscilloscope to better learn how to use it; I tried to measure the RC circuit in the image below with my 1202; I wanted to see the capacitor charging phase on the display.
Charging time should be approximately: 5xR1xC = 1-2 seconds
As soon as I close the left circuit, the capacitor immediately charges up to 9v, then the circuit remains at 9v with no current circulation.
I would have liked to have the full charge curve on the display, but I have not yet managed to capture it complete: sometimes I only have the screen of the final part of the charge ...
I guess I learned very little, I should have figured out how to capture the charge curve .. rejected! 

[tautech]

I update for the problem of saving the display images on a USB key in my sds1202: I bought 2 small keys (1GB), but I usually block the oscilloscope.
Now I am trying another method: the manual says to format FAT32, the I want to try to format FAT.
From the first tests it seems not to cause the problem, but I haven't tried many times; I will keep the situation updated!
 

Recently I read that a full format not a quick format will provide better results when having problems with USB sticks.

BTW, what OS is the PC you use running ?
Maybe format the sticks on another PC will give a different result.

[tautech]

I was playing with the oscilloscope to better learn how to use it; I tried to measure the RC circuit in the image below with my 1202; I wanted to see the capacitor charging phase on the display.
Charging time should be approximately: 5xR1xC = 1-2 seconds
As soon as I close the left circuit, the capacitor immediately charges up to 9v, then the circuit remains at 9v with no current circulation.
I would have liked to have the full charge curve on the display, but I have not yet managed to capture it complete: sometimes I only have the screen of the final part of the charge ...
I guess I learned very little, I should have figured out how to capture the charge curve .. rejected! 

Try dedicated Roll mode 500ms/div and Single trigger. Place the horizontal trigger position near the edge of the display if necessary.

[CharlotteSwiss]

Recently I read that a full format not a quick format will provide better results when having problems with USB sticks.

BTW, what OS is the PC you use running ?
Maybe format the sticks on another PC will give a different result.

thanks taut
I generally do quick formatting .. I had also tried slow formatting anyway, but then the problem happened anyway; my operating system is windows 8.1.
this new 1Gb key, I had formatted it for the first time Fat32, and immediately made the problem; I then saw on the PC that he had created the PNG folder, but empty ... obviously everything is fine until he creates the folder, then when he has to save the file it crashes (sometimes ..)

[tautech]

Recently I read that a full format not a quick format will provide better results when having problems with USB sticks.

BTW, what OS is the PC you use running ?
Maybe format the sticks on another PC will give a different result.

thanks taut
I generally do quick formatting .. I had also tried slow formatting anyway, but then the problem happened anyway; my operating system is windows 8.1.

OK, I used 8.1 for a while but don't remember now if there was problems but I don't think so.
On W10 now and no problems.
You may remember some many posts back I tried to replicate your problem and saved 40+ screenshots without any. I'm using cheap 8GB Strontium sticks.

[CharlotteSwiss]

Recently I read that a full format not a quick format will provide better results when having problems with USB sticks.

BTW, what OS is the PC you use running ?
Maybe format the sticks on another PC will give a different result.

thanks taut
I generally do quick formatting .. I had also tried slow formatting anyway, but then the problem happened anyway; my operating system is windows 8.1.

OK, I used 8.1 for a while but don't remember now if there was problems but I don't think so.
On W10 now and no problems.
You may remember some many posts back I tried to replicate your problem and saved 40+ screenshots without any. I'm using cheap 8GB Strontium sticks.

and I don't know; I spoke too soon; with Fat format, it slowed down my keys; but then you have to do Fat32.
I could try to use the key on windows 7 of the other pc for a while.

[CharlotteSwiss]

I was playing with the oscilloscope to better learn how to use it; I tried to measure the RC circuit in the image below with my 1202; I wanted to see the capacitor charging phase on the display.
Charging time should be approximately: 5xR1xC = 1-2 seconds
As soon as I close the left circuit, the capacitor immediately charges up to 9v, then the circuit remains at 9v with no current circulation.
I would have liked to have the full charge curve on the display, but I have not yet managed to capture it complete: sometimes I only have the screen of the final part of the charge ...
I guess I learned very little, I should have figured out how to capture the charge curve .. rejected! 

Try dedicated Roll mode 500ms/div and Single trigger. Place the horizontal trigger position near the edge of the display if necessary.

it was enough to use single and move the trigger point to the left; here the charge of the capacitor is captured. I didn't get there by myself
(this time the stick worked, slow formatting..but I don't know next time ...)

[CharlotteSwiss]

Important note for those wishing to buy this 1202x-e Siglent oscilloscope: I verified that with the latest firmware it has blocking problems by saving an image on a USB key; no problem with the penultimate firmware. If the engineers do not release further firmware after 1.3.26, I do not recommend purchasing this device!

[rstofer]

Nice display of charging waveform!

I would see about putting a vertical cursor at Tau = 1 and a horizontal cursor at 0.63*Vcc  They should intersect and cross the waveform at the same point.  Then display the cursor values (t and V).  Just as an exercise...

[CharlotteSwiss]

Nice display of charging waveform!

I would see about putting a vertical cursor at Tau = 1 and a horizontal cursor at 0.63*Vcc  They should intersect and cross the waveform at the same point.  Then display the cursor values (t and V).  Just as an exercise...

Nice to hear you rstofer, all right over there in America? 
I would do the exercise, but I didn't understand what is:  Tau=1
 

[rstofer]

Tau is the time constant and is equal to R * C.  You had the correct value up above.  Tau = 470 ms

Don't forget, all components have tolerances and electrolytic capacitors usually have a very wide tolerance.

The 63% output voltage may not occur at exactly 1 Tau.

Vout = Vin * (1 - e^(-t/Tau))  -- again, Tau = R*C  When t = Tau, t/Tau = 1 and Vout will be 0.63 (63%) of Vin

https://www.electronics-tutorials.ws/rc/rc_1.html

[rstofer]

At Desmos.com, I plotted y = 1 - e^(-x) and messed around with the X & Y range (use 'wrench' tool button)

Note that at x=1 (t = Tau) the value is 63%

[CharlotteSwiss]

Ok I didn't understand, I studied the constant long ago, from my notes: after a time constant, the capacitor voltage will be 27% of the starting voltage (example: if the capacitor voltage is 10v, after a time constant it will be 2.7v across it)
 

we can say that a capacitor is almost totally discharged after 10 time constants

[rstofer]

Ok I didn't understand, I studied the constant long ago, from my notes: after a time constant, the capacitor voltage will be 27% of the starting voltage (example: if the capacitor voltage is 10v, after a time constant it will be 2.7v across it)
 

we can say that a capacitor is almost totally discharged after 10 time constants

After a time constant, the capacitor should have 63% of the applied voltage.  We usually consider the capacitor charged in 5 or 6 time constants.

For time constants of 6 down to 1

1-e^(-6) = 0.997 or 99.7% charged
1-e^(-5) = 0.993 or 99.3% charged
1-e^(-4) = 0.982 or 98.2% charged
1-e^(-3) = 0.950 or 95.0% charged
1-e^(-2) = 0.864 or 86.4% charged
1-e^(-1) = 0.632 or 63.2% charged

The old HP48GX is getting a workout this morning!

If you play with Octave (free) or MATLAB, here is a simple script that prints a table of values

ETA:  And plots the charge and discharge curves...

Code: [Select]

V0 = 1; % assume a supply voltage
R = 10000; %10k Ohms
C = 0.1*10^-6; % 0.1 ufd
Tau = R*C;
t = linspace(0,8*Tau);
Vchg = V0 * (1 - exp((-t/Tau)));
Vdis = V0 * (exp((-t/Tau)));
plot(t, Vchg)
grid minor
grid on
hold on
plot(t,Vdis)
ylabel("Voltage")
xlabel("Time - seconds")
%there is a known bug in 'legend', the [h,~] is a kludge to work around it
[h,~]=legend("Charge Voltage","Discharge Voltage");
figure(gcf) % or shg command - pull plot to top
for Tau = 0:6
    pct_charge = V0 * (1 - exp((-Tau))); %percent charge
    fprintf("%% Tau = %.0f Percent Charge = %5.2f%%,\n", Tau, 100*pct_charge)
end


% Results appended to source

% Tau = 0 Percent Charge =  0.00%,
% Tau = 1 Percent Charge = 63.21%,
% Tau = 2 Percent Charge = 86.47%,
% Tau = 3 Percent Charge = 95.02%,
% Tau = 4 Percent Charge = 98.17%,
% Tau = 5 Percent Charge = 99.33%,
% Tau = 6 Percent Charge = 99.75%,
[/font]

[rstofer]

I was only working with charging.  For discharge, you can do 1-(charge percentage).  So, for a 1 Tau discharge, the percent of charge remaining is 1.000 - 0.632 and get a remaining charge of 36.8%.

I modified the script above to print the discharge voltage percentages as well.

Code: [Select]

Charge Voltage

% Tau = 0 Percent Charge =   0.00%,
% Tau = 1 Percent Charge =  63.21%,
% Tau = 2 Percent Charge =  86.47%,
% Tau = 3 Percent Charge =  95.02%,
% Tau = 4 Percent Charge =  98.17%,
% Tau = 5 Percent Charge =  99.33%,
% Tau = 6 Percent Charge =  99.75%,

Discharge Voltage

% Tau = 0 Percent Charge = 100.00%,
% Tau = 1 Percent Charge =  36.79%,
% Tau = 2 Percent Charge =  13.53%,
% Tau = 3 Percent Charge =   4.98%,
% Tau = 4 Percent Charge =   1.83%,
% Tau = 5 Percent Charge =   0.67%,
% Tau = 6 Percent Charge =   0.25%,
[/font]

[CharlotteSwiss]

great job rstofer: I don't understand where I had found that after a constant it was discharged up to 27% ...
However as soon as I have time I try with an RC circuit looking at the oscilloscope
 
thanks

[CharlotteSwiss]

I did a first test on the bench: RC circuit with 47K and 1000uF.
1T is 47s
So in theory after 47 seconds I should have had the capacitor charged at 3.15 volts (63%)
I only reached about 2.56v (51,2%). I guess it's part of the capacitor tolerance ..
Good night 

[2N3055]

I did a first test on the bench: RC circuit with 47K and 1000uF.
1T is 47s
So in theory after 47 seconds I should have had the capacitor charged at 3.15 volts (63%)
I only reached about 2.56v (51,2%). I guess it's part of the capacitor tolerance ..
Good night 

Hi!

Try this with a film or block (not electrolytic) capacitor. If you use 0.1uF it should charge in some 10s of miliseconds.. Scope is fast, you don't have to work on scale of minutes.
What you see might be electrolytic capacitor leakage (they should be ideal isolators for DC, but they are not) or dielectric absorption (soaking charge). Or even fact that capacitors change capacity depending of what DC voltage is applied to them (some have this effect very large, some very little).

Try shorting the electrolytic, and look at it with a scope.. It will "magically" "recharge again" to some smaller voltage,  i.e. it will release absorbed charge after some time.
That is why high energy and voltage capacitors should be kept shorted in storage, because they might "recharge back" to lethal voltages if they were used before on high voltages.

Play with different capacitor types, different resistors ( charge/discharge same capacitor at different speed ) and you will see that curves will differ from ideal ones, and they will change based on how you charge them (how fast, how deep you charge /discharge etc..). You will soon see that all of them are different and that is why we use different types for different purposes.

And that is only DC. Once you start looking at them at higher frequencies and discover that they are not "only capacitors" but actually a complex schematic, things get interesting...

Have fun on your journey of discovery....

Regards,

Sinisa

[CharlotteSwiss]

Have fun on your journey of discovery....

Regards,

Sinisa

thanks Sinisa, ok later i try with other capacitors (i think i have a set of ceramics)
I'll let you know
 

[tggzzz]

thanks Sinisa, ok later i try with other capacitors (i think i have a set of ceramics)

Some ceramic capacitors, especially small or high value MLCC construction, have a capacitance that is highly voltage dependent - some lose 90% of their capacitance at rated voltage. When that happens the response to a step voltage change is visibly non-exponential!

[CharlotteSwiss]

I only have electrolytic capacitors; ceramic ones are smd, difficult to use on breadboard 
however, come on I can experiment with the charge and discharge of capacitors using electrolytic, perhaps with low capacity; the important thing is to understand the theoretical formulas, then if in reality the measurement is different, patience.
 

[rstofer]

Let's assume your scope compensation signal is 1 kHz -> 1 ms for a complete square wave.  Each half cycle (for charge then discharge) is 500 us and we want that to equal 5 Tau so Tau (R*C) is 100 us.  We don't want to load the signal so let's pick a 1k series resistor.  We know Tau = R * C and Tau is 100*10^-6 and R = 1 * 10³

100*10^-6 = 1*10³*C or C =100*10^-9 or 100 nf or 0.1 ufd.

You could use a 1k resistor and a 100 nf ceramic to visualize on your scope both the charge and discharge waveform using your compensation signal. 100 us/div would be a good place to start.

This makes sense because the attached experiment used 80 Hz (much slower) but a higher resistor.  But I could dial in any frequency I wanted.

Unless you have a better source for a square wave...

I did this experiment when we were first discussing your scope.  I had a lower frequency source (80 Hz) so the components were:  R = 10k and C = 100 nf

[rstofer]

I only have electrolytic capacitors; ceramic ones are smd, difficult to use on breadboard 
however, come on I can experiment with the charge and discharge of capacitors using electrolytic, perhaps with low capacity; the important thing is to understand the theoretical formulas, then if in reality the measurement is different, patience.
 

All of this is true!  It's the math that matters, perfection can wait.  But somehow I get a warm feeling when the scope signal matches closely to the theory.

As I pointed out much earlier in your thread, I can spend a lot of time playing with a 0.1 ufd capacitor and a 10k resistor.  First, the forced response in the time domain (what we're looking at here) and then the low or high pass filter in the frequency domain (Bode' Plot).

If your SMD components were 0805, it might be possible to solder leads to the end caps.  I have never tried it.

[rstofer]

There is quite a fan club for 555 timer projects.

https://www.electronics-tutorials.ws/waveforms/555_oscillator.html

According to this calculator, R1 = 6.8k, R2 = 68k, C = 0.1 ufd will give 101 Hz, 52% Duty Cycle.  You can't get to exactly 50% duty cycle with this simple circuit but this is pretty close.  I am aiming for 80 Hz so it matches my Analog Discovery 2 experiment but this might be good enough.

I might use a potentiometer on R1.  I would want a 1k fixed series resistor so that the resistance can never be 0 Ohms so a 10k pot might be just about right.

https://circuitdigest.com/calculators/555-timer-astable-circuit-calculator

It's the 10:1 ratio of R1 to R2 that gives the nearly 50% duty cycle.

There's a 50% Duty Cycle circuit on the linked page above.  This is probably the better way to go.

Breadboarding something like this is pretty easy and will provide an opportunity for further scope experiments.