🚀 go-pugleaf

In article <-slj0+=.jps@netcom.com> jps@netcom.com (John Serafin) writes:
> sagerian@delphinium.UUCP (Steve M. Sagerian) writes:
> 
> >I fact I was supprised no one mention that aluminum (sp?) wheels have no effect on the sensor at all.
> 
> Then how does an aluminum frame with aluminum wheels trip sensors?
> (It happens frequently.)
> >Stever

These things (at least the more common type) detect eddy currents, which means
enough metal (regardless of whether it is magnetic or not).  It really senses
conductivity.

I watched them install one of these things in front of my old house, the sensor
is just a loop of wire (3-4 turns) placed into an approximately rectangular
saw cut into the pavement, then the cut is filled with tar.

This particular sensor could be triggered reliably with a piece of aluminum
foil placed over the sensor within a couple inches of the pavement.
This told me that magnetic materials are _not_ needed, as last I knew, aluminum
was not magnetic.

The sensitivity seemed to be proportional to the area of the sensee, and
being close to the pavement was also important.  The most sensitive
area seemed to be just inside the edge of the box.  Bikers take note.

-Mike