I need to build a fake metal detector type device for a museum installation. I am reasonably comfortable with Arduino and have used it for a handful of similar projects.
My task is to hide several sensors in the floor and build a receiver into a fake metal detector build by the props departement. Arduino should then bleep faster and faster as it gets closer to each sensor.
Can anyone suggest the correct type of sensor to use? Obviously ultrasound or infrared can't be used because they will just report the proximity of anything and everything.
What sensor devices can I use that will only report the proximity of this fake metal detector?