Gordon,

Just an FYI, I took a closer look at the last pic based circuit diagram from the geotech link today and there are a couple of small mistakes. The coil, R27 and IC3 should all be connected to the 9 volt rail not the 16 volt rail.

I'm thinking you could go for menu driven LCD, programmable presets and a selectable 'smaller; coil for pin pointing at the push of a button......oh and of coarse the obligatory flashing lights and bar graphs Hope you didnt want any sleep, hehehe

Regards,

Paul