|
Re: intuition behind a solution to crashing time domain simulation
#Time-step-too-small
开云体育I say try it in a circuit. Yes, SPICE ignores
case, but it doesn't ignore SPACES in this context. It ignores
any character after the space. 10f is 10F is 10 femtofarads: 10
f is 10 F is 10 is 10 farads. On 2025-02-24 23:32, Bell, Dave via
groups.io wrote:
--
OOO - Own Opinions only If something is true: * as far as we know - it's science *for certain - it's mathematics *unquestionably - it's religion |
||
|
Re: intuition behind a solution to crashing time domain simulation
#Time-step-too-small
开云体育OK, I tried it, and well, it’s weird and not as I expected. I stand corrected! ? Dave ? From: [email protected] <[email protected]>
On Behalf Of John Woodgate
Sent: Monday, February 24, 2025 3:23 PM To: [email protected] Subject: EXTERNAL: Re: [LTspice] intuition behind a solution to crashing time domain simulation #Time-step-too-small ? I think you have misunderstood. You can put a 10f (femtofarad) cap in an .ASC by writing that value in the component property pane. Try it: feed a 10f cap via 1meg and the -3dB point is at 16MHz. On 2025-02-24 23:00, Bell, Dave via groups.io wrote:
-- |
||
|
Re: intuition behind a solution to crashing time domain simulation
#Time-step-too-small
开云体育NOT if you type “10f”! That’s the same as “10F”, isn’t it? For time, resistance, etc.10m = 10M <> 10meg or 10Meg, etc. ? From: [email protected] <[email protected]>
On Behalf Of John Woodgate
Sent: Monday, February 24, 2025 3:23 PM To: [email protected] Subject: EXTERNAL: Re: [LTspice] intuition behind a solution to crashing time domain simulation #Time-step-too-small ? I think you have misunderstood. You can put a 10f (femtofarad) cap in an .ASC by writing that value in the component property pane. Try it: feed a 10f cap via 1meg and the -3dB point is at 16MHz. On 2025-02-24 23:00, Bell, Dave via groups.io wrote:
-- |
||
|
Re: intuition behind a solution to crashing time domain simulation
#Time-step-too-small
But, if that's the case, can it possibly mean 10 FARADS in ".options cshunt 10f" ?
toggle quoted message
Show quoted text
All of the other options default to values that make nearly no difference. -----Original Message-----
From: [email protected] <[email protected]> On Behalf Of David Schultz via groups.io Sent: Monday, February 24, 2025 3:11 PM To: [email protected] Subject: EXTERNAL: Re: [LTspice] intuition behind a solution to crashing time domain simulation #Time-step-too-small On 2/24/25 3:29 PM, Bell, Dave via groups.io wrote: Is “10f” a special case in the parasitics settings?Farads being the only possible unit for capacitance, there is no need to specify it. -- David Schultz "The cheeper the crook, the gaudier the patter." - Sam Spade |
||
|
Re: intuition behind a solution to crashing time domain simulation
#Time-step-too-small
开云体育I think you have misunderstood. You can put a
10f (femtofarad) cap in an .ASC by writing that value in the
component property pane. Try it: feed a 10f cap via 1meg and the
-3dB point is at 16MHz. On 2025-02-24 23:00, Bell, Dave via
groups.io wrote:
--
OOO - Own Opinions only If something is true: * as far as we know - it's science *for certain - it's mathematics *unquestionably - it's religion |
||
|
Re: intuition behind a solution to crashing time domain simulation
#Time-step-too-small
开云体育Yes, I agree, on all counts. It means Farads, in lower OR upper case. But in the .options context, it appears to accept 10f as 10 femtofarads. That’s logical, because who would want a 10F parasitic shunt capacitance? ? I’m just disturbed that it’s different, between contexts. Not much different from ^ vs. **, where the carat could mean exponentiation or exclusive OR ? ? From: [email protected] <[email protected]>
On Behalf Of John Woodgate
Sent: Monday, February 24, 2025 2:03 PM To: [email protected] Subject: EXTERNAL: Re: [LTspice] intuition behind a solution to crashing time domain simulation #Time-step-too-small ? I think that 10 means 10 farads, 10m means 10 millifarads etc, but, with a space in between, 10 f or 10 F or 10 m means 10 farads and the following letter is disregarded, or throws an error in some cases. This works in the component properties pane. On 2025-02-24 21:52, Bell, Dave via groups.io wrote:
-- |
||
|
Re: .MEAS Failure
开云体育On 24/02/2025 22:50, eewiz via
groups.io wrote:
No, that is not the case - wrong conclusion. Try again with: .options numdgt=15. By default, the .raw file is written with single precision; this option enables double precision (and approximately doubles the .raw file size). There was no test to see if data was ever == 2 as the .MEAS statement would imply.That's because the computation used interpolation - an estimation based on the closest two available data points, as previously stated. Obviously, there is no actual data point at exactly 2V. .MEAS can only make guesses on the data that actually exists in the .raw file, as it is a post-analysis calculation. There's no guarantee that any analysis can achieve a data point that shows V ≡ 2V, regardless of the maximum time step. This is why interpolation is used. That's just how the LTspice time step algorithm works. -- Regards, Tony |
||
|
Re: intuition behind a solution to crashing time domain simulation
#Time-step-too-small
开云体育I think that 10 means 10 farads, 10m means 10
millifarads etc, but, with a space in between, 10 f or 10 F or
10 m means 10 farads and the following letter is disregarded, or
throws an error in some cases. This works in the component
properties pane. On 2025-02-24 21:52, Bell, Dave via
groups.io wrote:
--
OOO - Own Opinions only If something is true: * as far as we know - it's science *for certain - it's mathematics *unquestionably - it's religion |
||
|
Re: intuition behind a solution to crashing time domain simulation
#Time-step-too-small
开云体育In *this case*, I see that. Seems like a bit inconsistent… ? From: [email protected] <[email protected]>
On Behalf Of John Woodgate
Sent: Monday, February 24, 2025 1:36 PM To: [email protected] Subject: EXTERNAL: Re: [LTspice] intuition behind a solution to crashing time domain simulation #Time-step-too-small ? 10f is recognized as 10 femtofarads. On 2025-02-24 21:29, Bell, Dave via groups.io wrote:
-- ?
|
||
|
Re: .MEAS Failure
Hello All:
?
.meas TooLow1 FIND V(XSW11:X1:Qc,XSW11:X1:Qe) WHEN V(XSW11:X1:Qc,XSW11:X1:Qe)=2 FALL=1
works and produces;
toolow1: v(xsw11:x1:qc,xsw11:x1:qe)=2 at 0.00804696
?
Zooming in the plot window to the end of the universe, I see this point.
8.0469636ms 2.0000203V
The next point is:
8.0469636ms 1.9999355V
The time values must have greater precision than can be seen because a node can't have two different voltages at the same time.
I now see that since there is no value in the data that is exactly 2.0000000 it had to perform a poor mans less-than function.
The code saw that 1.9999355 was less-than 2 where the previous sample 2.0000203 was more than two.
So that's a fall.
There was no test to see if data was ever == 2 as the .MEAS statement would imply.
I now see that the Fall and Rise modifiers mimic less-than or greater-than behavior for the .MEAS FIND WHEN statement.
?
All for now
?
Sent:?Monday, February 24, 2025 at 12:17 PM
From:?"eewiz via groups.io" <eewiz@...> To:[email protected] Subject:?Re: [LTspice] .MEAS Failure ?
Hello All:
?
Sorry for being late to the party but I had to grab some sleep time.
?
So, it's equality only.
No matter how many times I read the .meas help I would not come to that conclusion.
To me;?WHEN <expr> means WHEN <any and all types of mathematical experssion>.
WHEN <expr of equality only> would be much more redily understandable.
?
I noticed that there were no examples of anything like:
Print the time if and when a power exceeds 5W.
Print the time if and when a collector-emitter voltage goes less than 2V.
Print the time if and when a snubbed node ever exceeds 15.6V.
?
Those are always the type of questions that I regularly need answers to.
?
Thanks very much for the examples.
I will see if I can get the answers I need using only equality.
? All for now ?
Sent:?Monday, February 24, 2025 at 11:24 AM
From:?"Tony Casey via groups.io" <tony@...> To:[email protected] Subject:?Re: [LTspice] .MEAS Failure On 24/02/2025 15:57, Andy I via groups.io wrote:
But I distinctly recall Helmut Sennewald cautioning people not to test for equality.? Better to use >= or <=.? The implication was that it did not use linear interpolation in those situations.? I thought .MEAS was one of them.This would be the case, for example, in a B-source expression, which disallows the "=" operator anyhow, e.g.: ? B1 EQ0 0 V=if(V(test)=0,1,0) ..which triggers an error, but: ? B1 EQ0 0 V=if(V(test)==0,1,0) ..doesn't. However, in the example of my simple sine source circuit, the 2nd of those expressions only results in V(eq0)=1 once at time=0, because none of the following data points result in V(test)=0, even though it is clear the waveform is periodic and passes through zero twice every cycle. This example therefore doesn't use interpolation, it simply looks at each data point. -- Regards, Tony |
||
|
Re: intuition behind a solution to crashing time domain simulation
#Time-step-too-small
开云体育10f is recognized as 10 femtofarads. On 2025-02-24 21:29, Bell, Dave via
groups.io wrote:
--
OOO - Own Opinions only If something is true: * as far as we know - it's science *for certain - it's mathematics *unquestionably - it's religion |
||
|
Re: intuition behind a solution to crashing time domain simulation
#Time-step-too-small
开云体育Is “10f” a special case in the parasitics settings? For a regular cap, it would mean 10 Farads! ? From: [email protected] <[email protected]>
On Behalf Of john23 via groups.io
Sent: Monday, February 24, 2025 12:29 PM To: [email protected] Subject: EXTERNAL: Re: [LTspice] intuition behind a solution to crashing time domain simulation #Time-step-too-small ? ? ? The following line solved the problem.Is there some manual or intution regarding why these might help? .options cshunt =10f gshunt=10n abstol=10n vntol=1m ? Thanks. |
||
|
Re: intuition behind a solution to crashing time domain simulation
#Time-step-too-small
开云体育I don't know what's going on here. U1 isn't
open-loop. Are we looking at the same .ASC,
PID_section_united_AC_separate?? U3 is open-loop at DC. U1 and
U2 have unity gain, U4 has 100 times gain at DC. In such a
circuit, I would not expect a TSTS? error, and I would expect
the model o a costly opamp to be a good one. I meant that I
could not see how to verify node 38 without going back over the
previous many emails. On 2025-02-24 17:19, Andy I via
groups.io wrote:
--
OOO - Own Opinions only If something is true: * as far as we know - it's science *for certain - it's mathematics *unquestionably - it's religion |
||
John Woodgate
Bell, Dave
Tony Casey
eewiz
Carlo