Homebrew PCBs

That blocks interference but it can actually make leakage worse as the
path to ground is shorter.

No, haven't tried Teflon. Is it that good an insulator? What am I
using the stand-offs for? If you mean the supports for the PCB, that
still leaves me with surface leakage across the PCB.

Actually a driven guard ring will reduce the problems of leakage. If you are refering a grounded guard ring, you are correct. However most guard rings are driven to the same signal levels as the signal of interest in order to reduce problems with leakage.

You can get teflon for your pcb material instead of FR4, but it is a lot more expensive. Teflon also will hold a electrostatic charge and can create miuch havoc.

See
http://www.national.com/rap/Story/0,1562,4,00.html

for an example of how teflon can create a problem as it ages.

Best regards
Ron

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