On Tue, 25 Nov 1997 07:38:56 -0800 ERIC SCHLAEPFER
<eric.schlaepfer@AUTODESK.COM> writes:
>     Hi all,
>
>     Does anyone here happen to know a method to detect electrical
>contact
>     between two metal parts without having a ground return to
>complete the
>     circuit? I just want to see if anyone else has solved this
>problem
>     before.

You haven't described the problem very well.  If the measuring device
connects to a small, isolated metal object, which may or may not contact
a large metal object, then measuring the capacitance to "ground" may
work.  This is typically done by applying a high-frequency AC signal and
measuring the impedance.  The measuring unit's "ground" has to be
somewhat coupled to the large object.  It's a lot easier to use this as a
differential measurement, i.e. the measuring unit constantly adjusts
itself to the capacitance found and generates an output whenever a large
change is detected.

>
>     The reason it is on this list is because I will use a PIC to
>detect
>     this contact.

One way to do this would be to wire up an oscillator with the frequency
determining-network connected to the test probe, then use the PIC to
count the frequency and report any change.