Measuring settling time

[Anonymous]

Hi dear people,

I’m simulating a control system (with a PID regulator) with LTSPICE ver.4.21, and I’m trying to optimize. For each simulation I want to calculate the 5% settling time. I’ve found the .measure instruction inside a script file, but I can’t understand how it works. Is it possible to define a range of values (285-315) and calculate the time to enter in it without came out? The command

.MEAS TRAN SettlingTime5pc FIND V(Uscita) WHEN (V(Uscita)=285 || V(Uscita)=315) cross=last

doesn’t work. How can I define a range?

[Cribald]

Hello rbacchi,

You were on the right track. I’ve applied the .MEAS directive to this simple second order RLC circuit:
I’ve chosen the components values ​​to make it quite underdamped:

go to “View” menu, and click SPICE Error Log file (or CTRL+L).

the higher value is the settling time. If you want a 2% settling time, simply set settling_percent=2.

[Anonymous]

Magic Cribald,

your solution works perfectly!

Do you think may be possible to use an instruction that prints the max value between the two times?

Thank you a lot,

Roberto

[Cribald]

Ciao Roberto,

add directive:

.MEAS TRAN settling_time PARAM max(t_lo_settling,t_hi_settling)

[Anonymous]

Two times Magic!

It works perfectly!

Thank you a lot

Roberto

[Author]

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