Simulation of Transformer

Schematic Simulation (Ngspice)
1

I have a LVDT that I am trying to simulate. I have measured the resistance and inductance and created a schematic version.

Untitled

My ngspice commands are:

L1 1 2 501m
L2 2 1 1.043H
K1 L1 L2 0.498

The coupling factor of 0.498 I obtained from measurement by applying a sine wave to the input coil on the real device.

My circuit works but I should be able to see a change in the circuit operation if I change the coupling factor, and I don’t.

I’ve tried a factor of 0.398 and 0.598 and the response of the circuit is identical.

I’ve tried commenting out the L1 and L2 lines and that has no effect, the circuit operation remains the same. Are they needed?

Any general suggestions on what I might be doing wrong?

Thanks!

2

Update:

I can remove the values from the components and comment out the L1, L2 and K1 lines and it still gives the same output!

If I put the K1 line back in I can change the coupling ratio from 0.1 to 1.0 and it makes no difference.

Weird.

3

I don’t think there’s enough information here to help. Can you post the entire schematic? Either the whole screenshot or the .SCH file or the whole zipped project folder.