[SI-LIST] : Re: Differential measurements

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From: Fred Balistreri (fred@apsimtech.com)
Date: Thu Mar 02 2000 - 13:05:00 PST


Steve in the case of the PCB structure the plane is there and
cannot be ignored by the signal. When you choose not to tie
the plane to the TDR gnd lead you are essentially floating the
plane. By doing this you are forcing a higher impedance path
for the currents to return to. The high frequency currents will
capacitively couple to their final destination but the path is
a bit higher impedance than a direct connection.

The theorically answer in number 2 correct. The two are the
same. However as mentioned there are practical considerations.
If a gnd is nearby then the measurement will be influenced by
the gnd.

excuse the typos.

best regards,

Ting, Steve (Bnd) wrote:

> Part 1.1Type: Plain Text (text/plain)

--
Fred Balistreri
fred@apsimtech.com

http://www.apsimtech.com

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