LTSpice - enveloping curve - series RLC circuit

Thread Starter

Bharath12

Joined Nov 15, 2018
18
Hello everyone,

I have built a simple RLC circuit and a behavioral voltage source as shown in the circuit. I am interested in the output of the behavioral source. Since the system is an under-damped system the amplitude reduces over time. I want to plot the enveloping curve of the same and calculate the damping factor and damping coefficient. Can anyone please help me with it.

Thanks in advance
 

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Alec_t

Joined Sep 17, 2013
10,362
How about this?
I changed R1 to show the envelope better. The R2C2 time constant was chosen as 5 x the oscillation period.
Envelope.PNG
You could use the .MEASURE command to sample the envelope waveform at intervals for your calculations.
 

Thread Starter

Bharath12

Joined Nov 15, 2018
18
How about this?
I changed R1 to show the envelope better. The R2C2 time constant was chosen as 5 x the oscillation period.
View attachment 173085
You could use the .MEASURE command to sample the envelope waveform at intervals for your calculations.
Hi Alec_t, thanks for going through it. I cannot change it. Those are the values I need to insert as part of my task. So can you suggest any other means to get the enveloping curve? And how to use the .MEASURE command to sample the waveform?
 

Alec_t

Joined Sep 17, 2013
10,362
I cannot change it.
Just put R1 and the simulation time back to what you had. V1, L1, C1 are unchanged (although V1 is expressed in an easier-to-read format).
The LTS Help explains the use of .MEASURE.
 

ericgibbs

Joined Jan 29, 2010
8,733
hi 12,
This needs the Source to have a internal resistance of 0.1R, the same as your earlier thread dealing with a mechanical system.
E
AA1 24-Mar-19 08.40.gif
 

Thread Starter

Bharath12

Joined Nov 15, 2018
18
hi 12,
This needs the Source to have a internal resistance of 0.1R, the same as your earlier thread dealing with a mechanical system.
E
View attachment 173146
Hi ericgibbs, thank you for replying. After adding the internal resistance how can I get the enveloping curve and calculate the damping factor and damping coefficient from the waveform?
 
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