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Author Topic: The Inventions of Willi von Unruh and Hans Coler  (Read 1272 times)

Group: Elite Experimentalist
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Posts: 2235

Smudge,

with the below video i want to show what happens when using the grounded FG and scope leads (forming
a groundloop) when using a 1K load on the output while sweeping (1Khz to 20Mhz) the input.

The signal amplitude and resonance point shifts  when unhooking the scope groundleads and even when
swapping the output probe tip / groundlead.

In the end i switchover to a differential probe measurment for the output, so without a groundloop
showing a fairly flat frequency resonse (up till 50Mhz) across this iron coil setup.


Video here:  https://www.youtube.com/watch?v=z_ZyWHKXXYU

I do notice that LTspice demands each node to be grounded, so not sure why that is as we then cannot
simulate a floating node like we have here.


Itsu   
   
Group: Experimentalist
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Posts: 1150
Smudge,

with the below video i want to show what happens when using the grounded FG and scope leads (forming
a groundloop) when using a 1K load on the output while sweeping (1Khz to 20Mhz) the input.

The signal amplitude and resonance point shifts  when unhooking the scope groundleads and even when
swapping the output probe tip / groundlead.

In the end i switchover to a differential probe measurment for the output, so without a groundloop
showing a fairly flat frequency resonse (up till 50Mhz) across this iron coil setup.


Video here:  https://www.youtube.com/watch?v=z_ZyWHKXXYU

I do notice that LTspice demands each node to be grounded, so not sure why that is as we then cannot
simulate a floating node like we have here.


Itsu

Itsu,

In LtSpice you do not need to necessarily use a zero ground but you can use a very high value resistor to ground instead say like a 10Megohm.  This allows the initial dc tests of the simulator to be done without error and lets you simulate a "floating" ground.

Regards,
Pm
   

Group: Elite Experimentalist
Hero Member
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Posts: 2235

Thanks PM,   good to know, i will try that.

Itsu
   
Group: Moderator
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Posts: 1378
Itsu,
Here's my take on this.  The image below shows the capacitive coupling across the two coils and how the ground loop plays its part.  You get multiple capacitors from turns to turns whereas I only show one.  So it matters which end of the secondary is grounded giving different results.  For the differential measurement the 10M scope probe kills any ground loop effect.
Smudge
   

Group: Elite Experimentalist
Hero Member
*****

Posts: 2235

I agree Smudge, and by putting a scope groundlead at the FG ground directly (during input measurements),
one shorts out or shortens this ground path, impacting the resonance frequency (12.5Mhz to 10Mhz).

Thanks Itsu
   
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