General > General Technical Chat
FFT in LTSPICE XVII - force settings
fcb:
Is there a way to force the setting of the FFT in LTspice (using XVII).
I'm already using the .four operative to create THD readouts successfully and also the FFT (View>FFT).
Problem is that it (FFT) doesn't seem to remember my 'specify a time range/time range' choices and requires resetting every simulation run (although it does remember my choice of window?).
?Any ideas if their are some operatives/instructions to force the the FFT?
SiliconWizard:
IIRC, the View/FFT computes an FFT over the portion of signal in the current window by default. I don't think there is any other way to make it "remember" the time range. So your best bet, if you want to issue an FFT over a specific time range, would be to define this time range in the transient simulation (time to start saving data/stop time).
fcb:
Thanks SiliconWizard.
That fix does work and is saving my sometime. Still be nice if their were .op options to force the settings of the FFT, perhaps someone from LT/AD will read this.
Jay_Diddy_B:
--- Quote from: fcb on May 18, 2020, 09:37:02 am ---Is there a way to force the setting of the FFT in LTspice (using XVII).
I'm already using the .four operative to create THD readouts successfully and also the FFT (View>FFT).
Problem is that it (FFT) doesn't seem to remember my 'specify a time range/time range' choices and requires resetting every simulation run (although it does remember my choice of window?).
?Any ideas if their are some operatives/instructions to force the the FFT?
--- End quote ---
Can you share your model? or an example with the same challenges?
There may be a solution.
Regards,
Jay_Diddy_B
fcb:
Sorry Jay_Diddy_B. It's under a fairly draconian NDA.
For anybody else searching how to do an FFT or THD (.four) using LTspice, this is the main resource I used:
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