LIMP impedance and T/S parameters shift

[adamharzuf]

Hello all,
I'm using LIMP with the ARTA box.
I'm getting the impedance peaks in higher frequencies then I should, for example the Hertz 165DSK.

Also there's a slight noise apparent in the response - why is that? I've checked all my grounds in the jig and the cables as well. Maybe I missed something?

Thanks
Adam

[Sydney]

Re: LIMP impedance and T/S parameters shift

Does the noise appear consistent - regardless of where and how the DUT is placed?
( blips can be caused by reflections )

[adamharzuf]

Re: LIMP impedance and T/S parameters shift

well it moves a bit on the screen every frame (LIMP's refresh rate).
I'm moving the driver around within about a meter, vertical horizontal etc. but the pattern stays the same.
It's also apparent when measuring a resistor.

[Sydney]

Re: LIMP impedance and T/S parameters shift

How is driver positioned?

[adamharzuf]

Re: LIMP impedance and T/S parameters shift

Open air. moving it doesn't change measured FS frequency.

[Sydney]

Re: LIMP impedance and T/S parameters shift

I thought perhaps there was an "outside influence" creating noise

[adamharzuf]

Re: LIMP impedance and T/S parameters shift

As I said, the noise is there with resistors (or capacitors) as well..
Thanks anyway

[1100xxben]

Re: LIMP impedance and T/S parameters shift

This may be a long shot, but if you're using a laptop, try unplugging the power supply and run solely off the battery.

[Sydney]

Re: LIMP impedance and T/S parameters shift

This may be a long shot,

Maybe not...
I was surprised ( with my WT2 ) how sensitive it was.
I turned off nearby devices.

[adamharzuf]

Re: LIMP impedance and T/S parameters shift

This may be a long shot, but if you're using a laptop, try unplugging the power supply and run solely off the battery.

Stays the same between my laptop and desktop..

[adamharzuf]

Re: LIMP impedance and T/S parameters shift

Anyone?

[John L. Murphy]

Re: LIMP impedance and T/S parameters shift

Hello all,
I'm using LIMP with the ARTA box.
I'm getting the impedance peaks in higher frequencies then I should, for example the Hertz 165DSK.

Also there's a slight noise apparent in the response - why is that? I've checked all my grounds in the jig and the cables as well. Maybe I missed something?

Thanks
Adam

If the noise level is fairly constant then look for a way to increase the test signal level. This will to increase the overall signal-to-noise ratio and reduce the noise artifacts on the impedance plot. What is the level of the test signal? Somewhere around 1 Vrms should provide reasonable noise immunity depending on the test setup.

Regards,

John