# LTS Analysis of RLC circuit and Testing w/o GND loop

#### WBahn

Joined Mar 31, 2012
26,398
Capacitance measured with Vici VC8145 bench meter (also inductor R) and inductor with a GM328 Multi-use Transistor Tester for inductance. On my SZJB BM4070 LCR meter, I get 30.7mH & 76.1Ω for the inductor and 8.3nF on the cap. So the values are very close for both instruments. I can only assume from the calculation results that there might be some error for cap and inductor but the big error is for the resistor? Which measures at less than 1% error than the ideal 1kΩ marked. I could have swapped the resistor but swapping out the cap seemed to resovle measuring Vpp across it with the Oscope.
When you say that the big error is for the resistor, is that when you are using the nominal values for all of the components, or the measured values for them?

#### SamR

Joined Mar 19, 2019
3,612
For Vr
Nominal: 5.78V
Actual: 4.61V
Meas: 3.76V

Small difference but a large error.

Edit: now that I stop and think about it any small error in L or C gets magnified in the Z calculation used to determine current. But then it is also used to calculate the V for L and C so it becomes a circular argument? No because of the magnitude of V for L and C it would be a smaller error than for Vr?

Last edited:

#### SamR

Joined Mar 19, 2019
3,612
@crutschow Is there a way to output a textfile from LTS showing Vpp, Vmax, Vmin, phase, same for I, for each trace?

#### Jony130

Joined Feb 17, 2009
5,251
Try AC analysis for a single frequency
Code:
.ac oct 1 6k 6k
But do not forget that the components in the simulation have a "polarity".

#### SamR

Joined Mar 19, 2019
3,612
Bingo! Thx Jony!

#### Jony130

Joined Feb 17, 2009
5,251
I have an off-topic question.

Why you (Americans) you don't like to use nF ?

Last edited:

#### SamR

Joined Mar 19, 2019
3,612
No particular reason although some vendors don't list components in nF or mH instead listing as 100'000uH and .001uF. I would actually prefer mH and nF. Back to LTS is there a way to print the AC Analysis directly from LTS? I've snipping and printing a screenshot to get it.

#### Jony130

Joined Feb 17, 2009
5,251
Back to LTS is there a way to print the AC Analysis directly from LTS? I've snipping and printing a screenshot to get it.
I don't know. But Ctrl+c and Ctrl+v works.

#### SamR

Joined Mar 19, 2019
3,612
No it only copies the schematic. Ahhh LTS works w/ n, good.

#### WBahn

Joined Mar 31, 2012
26,398
For Vr
Nominal: 5.78V
Actual: 4.61V
Meas: 3.76V

Small difference but a large error.

Edit: now that I stop and think about it any small error in L or C gets magnified in the Z calculation used to determine current. But then it is also used to calculate the V for L and C so it becomes a circular argument? No because of the magnitude of V for L and C it would be a smaller error than for Vr?
But
I have an off-topic question.

Why you (Americans) you don't like to use nF ?

My guess is that it is just tradition. Since capacitances span such a huge range of values, limiting the units used arguably makes it easier for people to more quickly grasp relative sizes. So you express all but the smallest (pF-scale) and largest (F-scale) values with a single unit (uF) for everything from 0.001 uF to 470,000 uF.

I personally prefer using engineering prefix convention on most things unless there's a specific reason not to.

#### SamR

Joined Mar 19, 2019
3,612
Why you (Americans) you don't like to use nF ?
Been thinking about why I adopted the .u notation. As I said I actually prefer to use n. Most of the books/texts that I have worked with use the .u notation and that was what was used in the lab manual for this exercise and I blindly used it when I copied the circuit into LTS. Fell into a bad habit? Strange because the books use mH and most vendors use uH instead? No solid sense of conformity here. I don't think I have ever seen a nano-sized cap used for anything but the capacitive grounding of ac or a pico-sized used for anything.

#### OBW0549

Joined Mar 2, 2015
3,566
Why you (Americans) you don't like to use nF ?

Habit/tradition. Nothing more than that. And going back a ways, we didn't even use pF; we used μμF instead. And we spoke of "cycles per second" instead of "Hz."

I feel old.

#### crutschow

Joined Mar 14, 2008
28,204
Is there a way to output a textfile from LTS showing Vpp, Vmax, Vmin, phase, same for I, for each trace?
Click on the plot window and then use File/Export.

#### crutschow

Joined Mar 14, 2008
28,204
And going back a ways, we didn't even use pF; we used μμF instead. And we spoke of "cycles per second" instead of "Hz."
Yes, I also remember well those days of μμF capacitors and kc frequencies (c was often incorrectly used for cps).

Another oldie.

#### WBahn

Joined Mar 31, 2012
26,398
Habit/tradition. Nothing more than that. And going back a ways, we didn't even use pF; we used μμF instead. And we spoke of "cycles per second" instead of "Hz."

I feel old.
And since typewriters didn't have a 'μ' symbol a 'u' was (and still is) commonly used, but another alternative was to write μF as mmF. I gave a teacher some grief (because he came up in the trades when mmF and uuF were very common) and so on a test I gave an answer in mmmmF instead of pF. When it was marked down (partially), I objected arguing that if it was acceptable to use mmF (in direct violation of the S.I. guidelines), then mmmmF had to be considered acceptable, too. He gave me the points back on the condition that I agree not to pull that crap any further.

#### The Electrician

Joined Oct 9, 2007
2,866
And since typewriters didn't have a 'μ' symbol a 'u' was (and still is) commonly used, but another alternative was to write μF as mmF. I gave a teacher some grief (because he came up in the trades when mmF and uuF were very common) and so on a test I gave an answer in mmmmF instead of pF. When it was marked down (partially), I objected arguing that if it was acceptable to use mmF (in direct violation of the S.I. guidelines), then mmmmF had to be considered acceptable, too. He gave me the points back on the condition that I agree not to pull that crap any further.
MMF was not an abbreviation for microfarad, which it might have been if the M was an abbreviation for milli-.

MMF (sometimes MMFD) was an abbreviation for micromicrofarad.

Here is a picture of an old mica capacitor with the value 47 MMF printed on it:

Just to make sure it's not a 47 millimillifarad capacitor, I measured it on an LCR meter:

It really is a 47 (nominal) pF capacitor--MMF stood for micromicrofarad in the old days.

#### WBahn

Joined Mar 31, 2012
26,398
MMF was not an abbreviation for microfarad, which it might have been if the M was an abbreviation for milli-.

MMF (sometimes MMFD) was an abbreviation for micromicrofarad.

View attachment 184919

Here is a picture of an old mica capacitor with the value 47 MMF printed on it:

View attachment 184920

Just to make sure it's not a 47 millimillifarad capacitor, I measured it on an LCR meter:

View attachment 184921

It really is a 47 (nominal) pF capacitor--MMF stood for micromicrofarad in the old days.
Yep, I believe you are correct. I was misremembering it (it's been decades since I've seen that).