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Subject: [SI-LIST] : Trace Capacitance
Author: Non-HP-Farrokh.Mottahedin (Farrokh.Mottahedin@quantum.com) at
HP-Boise,mimegw18
Date: 6/21/99 8:59 AM
I hope someone can explain what is happening with the following capacitance
measurement. A friend asks if capacitance is directly proportional to
surface area, why doesn't his measurement scale linearly. On a pcb made
specifically for trace characteristics measurement, he measures
1) 10 pf for a 10 cm long trace that is 5 mils (.12 mm) wide
2) 25 pf for a 10 cm long trace that is 20 mils (.50 mm) wide
3) Both traces are far apart from each other and from other components.
4) Both traces are over a solid ground plane.
5) Equipment is HP 4285A Precision LCR meter set at 1 MHz
Thanks,
Farrokh Mottahedin
Quantum Corporation
(408) 324-7934
farrokh.mottahedin@quantum.com
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