On 2/16/2010 3:38 PM, Jim Lux wrote:

...
Other references exist, ...

http://www.geotech1.com/pages/mag/pr...huggard300.pdf

I would never use a relay to switch from polarizing current to detection
mode on the sensor\coil ... even a simple two transistor flip-flop would
be immensely preferable.

Regards,
JS