On Jul 17, 2023, at 1:10 PM, Dan via <danniejackson@...> wrote:

You can lable the nets with numbers or letters.? As for them showing up as you mentioned I am not sure about that.

On Jul 17, 2023, at 1:01 PM, Jim Wagner <wagnejam99@...> wrote:

Those run-time node and net numbers can vary from run to run, especially after adding a component. AFIK, they are not known until the sim runs.

Jim, Oregon Research Electronics

On Jul 17, 2023, at 12:33 PM, Chris - G0LOJ <chrisbudd606@...> wrote:

I believe that nodes (or nets) can be user-named, and that curves on an LTSpice plot can also be user-named, but sometimes it would be simplest to use the node numbers assigned by the software during the building of a schematic. Is there a way to cause those node numbers to be displayed on the schematic. Thanks, Chris.

On Jul 17, 2023, at 12:33 PM, Chris - G0LOJ <chrisbudd606@...> wrote:

I believe that nodes (or nets) can be user-named, and that curves on an LTSpice plot can also be user-named, but sometimes it would be simplest to use the node numbers assigned by the software during the building of a schematic. Is there a way to cause those node numbers to be displayed on the schematic. Thanks, Chris.

?

Dave wrote, "Certainly slowed down the entire .TRAN period, though."

That should not have happened.? It should slow it down over only 1 ps of the 10 ms simulation -- so about 0.00000001% of it.

LTspice says it took about 0.4 seconds longer to simulate.? What did it do on your computer?

I wonder if we have run across another bug??? If you plot V(B), what do you see?

Anyway, just to clarify, when you wrote "but no longer works below 10ps!"? That's not quite true.? Your PULSE voltage source does have wicked fast rise and fall times down to 1 femtosecond or faster if you ask for them, but the internal Timestep isn't able to show it.? THAT is the issue, not the PULSE source.

Andy

?

That's the whole point of V2: it forces LTspice to have a very small timestep indeed. Obviously it takes time to plot lots of cycles of 1 petahertz.

Andy, your model here does work all the way down to 1fs.

But:

1. It’s much slower as-is, so
2. I deleted the SIN source, V2/B

Now, it runs as fast as before, as far as I could sense (didn’t compare runtime in the logs), but no longer works below 10ps!

?

Dave

?

From: [email protected] <[email protected]> On Behalf Of Andy I
Sent: Sunday, July 16, 2023 12:58 PM
To: [email protected]
Subject: EXTERNAL: Re: : Re: [LTspice] PULSE default rise and fall times (Trise=0 Tfall=0) (was: ISL70444SEH declaration issue?)

?

For grins, here is another one to try.? It shows one way to control SPICE's internal timestep while not imposing a harshly small Maximum Timestep across the whole simulation (which would make it crawl):

V1 A 0 PULSE(0 1 4m {Trf} {Trf} 1m 2m)

V2 B 0 SIN (0 1 1000T 4m 0 0 1000)

.step param Trf list 1f 10f 11f 20f 50f 100f 1p

.meas T0 WHEN V(A)=0.01 rise=1

.meas T1 WHEN V(A)=0.99 rise=1

.meas Td param T1-T0

.tran 0 10m

.options plotwinsize=0

Measurement: td

? step t1-t0

? ? ?1 1.01915e-015? <-- 1.02 fs

? ? ?2 9.80032e-015? <-- 9.8 fs

? ? ?3 1.07796e-014? <-- 10.8 fs

? ? ?4 1.95998e-014? <-- 19.6 fs

? ? ?5 4.90007e-014? <-- 49.0 fs

? ? ?6 9.79997e-014? <-- 98.0 fs

? ? ?7 9.8e-013? <-- 0.98 ps

Andy

Andy, your model here does work all the way down to 1fs.

But:

1. It’s much slower as-is, so
2. I deleted the SIN source, V2/B

Now, it runs as fast as before, as far as I could sense (didn’t compare runtime in the logs), but no longer works below 10ps!

?

Dave

?

From: [email protected] <[email protected]> On Behalf Of Andy I
Sent: Sunday, July 16, 2023 12:58 PM
To: [email protected]
Subject: EXTERNAL: Re: : Re: [LTspice] PULSE default rise and fall times (Trise=0 Tfall=0) (was: ISL70444SEH declaration issue?)

?

For grins, here is another one to try.? It shows one way to control SPICE's internal timestep while not imposing a harshly small Maximum Timestep across the whole simulation (which would make it crawl):

V1 A 0 PULSE(0 1 4m {Trf} {Trf} 1m 2m)

V2 B 0 SIN (0 1 1000T 4m 0 0 1000)

.step param Trf list 1f 10f 11f 20f 50f 100f 1p

.meas T0 WHEN V(A)=0.01 rise=1

.meas T1 WHEN V(A)=0.99 rise=1

.meas Td param T1-T0

.tran 0 10m

.options plotwinsize=0

Measurement: td

? step t1-t0

? ? ?1 1.01915e-015? <-- 1.02 fs

? ? ?2 9.80032e-015? <-- 9.8 fs

? ? ?3 1.07796e-014? <-- 10.8 fs

? ? ?4 1.95998e-014? <-- 19.6 fs

? ? ?5 4.90007e-014? <-- 49.0 fs

? ? ?6 9.79997e-014? <-- 98.0 fs

? ? ?7 9.8e-013? <-- 0.98 ps

Andy

?

For grins, here is another one to try.? It shows one way to control SPICE's internal timestep while not imposing a harshly small Maximum Timestep across the whole simulation (which would make it crawl):

?

Neon pilot lights were always used with a series resistor.

John wrote, "...?because it would probably explode due to excessive current if it ever reached striking voltage."

Interesting point.

But I think it would depend on the impedance of the source of the overvoltage.? If it's a transient overvoltage, presumably the source of that transient does not have the same low impedance as the mains supply itself.? (Unless it was something like the HV wire falling and shorting to the regular mains wire.)

I'm not trying to advocate putting a gas discharge tube directly across an AC mains line without a fuse or breaker.? I'm just playing the "what-if" and wanting to understand what goes on.

Andy

John wrote, "...?because it would probably explode due to excessive current if it ever reached striking voltage."

Interesting point.

But I think it would depend on the impedance of the source of the overvoltage.? If it's a transient overvoltage, presumably the source of that transient does not have the same low impedance as the mains supply itself.? (Unless it was something like the HV wire falling and shorting to the regular mains wire.)

I'm not trying to advocate putting a gas discharge tube directly across an AC mains line without a fuse or breaker.? I'm just playing the "what-if" and wanting to understand what goes on.

Andy

John wrote, "...?because it would probably explode due to excessive current if it ever reached striking voltage."

Interesting point.

But I think it would depend on the impedance of the source of the overvoltage.? If it's a transient overvoltage, presumably the source of that transient does not have the same low impedance as the mains supply itself.? (Unless it was something like the HV wire falling and shorting to the regular mains wire.)

I'm not trying to advocate putting a gas discharge tube directly across an AC mains line without a fuse or breaker.? I'm just playing the "what-if" and wanting to understand what goes on.

Andy

Tom wrote, "The gas tubes respond in several microseconds."

That's nothing compared to 8.33 milliseconds, unless your definition of "several" differs from mine.? Therefore the arc should extinguish between one half-cycle and the next.? If the next half-cycle also has a large over-voltage event, then of course it would trigger again, and again ... as expected.

All the comments about limiting the current during an over-voltage event are of course valid but that's true for any device that limits an over-voltage condition, whether a gas discharge tube or anything else.? Of course.? It's common sense, but it's unrelated to it being a gas discharge tube.

I still do not see why one should "never use a gas discharge tube across an AC ... line."? I do not believe that is a correct argument.? Once they fire they will self-extinguish before the next half-cycle begins.? Now if it was a DC line, that's another thing.

Andy