need help

need help - Messaggi

#1 Pubblicato: 09/05/2026 08:35:16
Andreas Beldowski

Andreas Beldowski

0 apprezzamenti in 17 post.

Gruppo: User

Hello,

unfortunately, I can't find the error myself. Why VS(t) and VRG58(t) work well, but V1(t):=VS(t)-VRG58(t) not?

Regards Andreas

Auszug.pdf (114,69 KiB) scaricato 402 volta(e).
Auszug.sm (16,52 KiB) scaricato 521 volta(e).
#2 Pubblicato: 09/05/2026 09:14:00
sergio

sergio

127 apprezzamenti in 342 post.

Gruppo: User

It seems that the two quantities have different units of measurement.
Solver_FXLZ2iLlqC.png
sergio
#3 Pubblicato: 09/05/2026 12:44:41
Andreas Beldowski

Andreas Beldowski

0 apprezzamenti in 17 post.

Gruppo: User

Thanks Sergio,

wrong was VRG58(t):=Ig(t)*(1/ZLRG58+1/RRG58)

right is VRG58(t):=Ig(t)*(ZLRG58+RRG58)

Regards Andreas
#4 Pubblicato: 10/05/2026 05:52:13
Andreas Beldowski

Andreas Beldowski

0 apprezzamenti in 17 post.

Gruppo: User

Hello,

and here’s another problem. Why does the differential of V1(t) work, but not that of V2(t)?

Both are sine functions; later, I’d like to try using square-wave functions as input as well.

For V1 and V2, I need the peak-to-peak amplitude and the phase difference between the two. I want to see if I can get better approximations for determining C1 by taking RG58 and the probe tip’s internal resistance into account in the measurement results.

Regards Andreas

Translation of “Der Wert ist oberhalb der maximalen Grenze für positive Zahlen” = “The value is above the maximum limit for positive numbers”

Versuch mit R und C mit Oszi.pdf (982,36 KiB) scaricato 357 volta(e). The value is above the maximum limit for positive numbers.gif Versuch mit R und C mit Oszi.sm (131,13 KiB) scaricato 525 volta(e).
Modificato 10/05/2026 06:01:03
#5 Pubblicato: 10/05/2026 08:15:12
StvMath

StvMath

44 apprezzamenti e 1 disapprezzamenti in 76 post.

Gruppo: User

"Why does the differential of V1(t) work, but not that of V2(t)?"

It's a combination of the size of the numbers and the order in which SMath does its calculations. Try:

dV2dt.png
#6 Pubblicato: 10/05/2026 10:41:34
Andreas Beldowski

Andreas Beldowski

0 apprezzamenti in 17 post.

Gruppo: User

Yeah, that's how it works for me, too.
#7 Pubblicato: 12/05/2026 13:09:32
Andreas Beldowski

Andreas Beldowski

0 apprezzamenti in 17 post.

Gruppo: User

It's me again, with a new problem.

Why doesn't the last line work, when the four lines above it do?

Versuch mit R und C mit Oszi Auszug.gif Versuch mit R und C mit Oszi Auszug.pdf (910,43 KiB) scaricato 346 volta(e). Versuch mit R und C mit Oszi Auszug.sm (130,35 KiB) scaricato 501 volta(e).
#8 Pubblicato: 13/05/2026 02:13:04
Alvaro

Alvaro

1.139 apprezzamenti in 1.805 post.

Gruppo: User

Hi. I have no idea why it fails, however this may be a workaround, consisting of directly applying the Newton-Raphson method.

image.png

Versuch mit R und C mit Oszi Auszug.sm (121,16 KiB) scaricato 490 volta(e).

Best regards.
Alvaro.
#9 Pubblicato: 13/05/2026 05:47:01
Andreas Beldowski

Andreas Beldowski

0 apprezzamenti in 17 post.

Gruppo: User

And why can I only use the values for LV1 and LV2 once, but the values for LdV1dt and LdV2dt multiple times?
I had already deleted the `clear()` statements, but that wasn't the problem.

Versuch mit R und C mit Oszi 3.gif
Modificato 13/05/2026 05:48:52
#10 Pubblicato: 13/05/2026 09:41:38
Alvaro

Alvaro

1.139 apprezzamenti in 1.805 post.

Gruppo: User

Hi. Use eval:

image.png

Best regards.
Alvaro.
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