Science Fair Projects on How Metal Detectors Work

You can’t go wrong with a colorful, easy-to-follow diagram describing the main components of a VLF metal detector. Use a large, three-pane poster board and include large, labeled drawings of the receiver and transmitter. Make both of these images cutaway drawings to show your visitors the respective coils of wire hidden inside -- the transmit coil and receiver coil. Explain that the transmit coil uses a fluctuating electric current to create an electromagnetic field, which points to the ground and helps reveal metallic objects by inducing a flow of current inside them. This flow of current is then received, isolated from the machine’s general electromagnetic field and amplified via the metal detector’s receiver coil.

The ideal metal detector science fair project should feature a fully functional, full-size metal detector. After explaining the basics about how the machine’s transmitter and receiver work together to identify metallic objects, do a demonstration of your metal detector’s functionality. Set three large bowls on your demonstration table -- one filled with sand, one with wood and one with metallic objects. Demonstrate for your audience how the metal detector fails to respond to the sand and wood bowls because they contain no metal to hold a current. Then place your metal detector’s transmitter above the bowl of metal to demonstrate how the device responds.

Doing a rehearsed presentation about the inner workings of a metal detector can hold your audience’s attention, but getting the audience physically involved in your project will leave a lasting impression on participants. Play a timed game with audience members. You’ll need a large sandbox filled with sand and a single metallic object. After explaining the basics of how a metal detector works, hand your metal detector to a volunteer and have her use the machine to find the metal object in the sandbox. Time the participant with a stopwatch. Keep a whiteboard nearby and use it to display the fastest times. This will turn your science fair project into an engaging competition.

Different types of metallic objects exhibit their own specific phase shift when encountering a metal detector’s electromagnetic field. An empty soda can creates a different signal than a silver dollar. Certain types of metal detectors can be set to acknowledge only a specific phase shift and to ignore all others. If your metal detector has this function, you can demonstrate this process as part of your science fair project. Fill a large sandbox with sand, crushed soda cans and a bunch of quarters and dimes. After explaining the basics to your audience, perform a demonstration in which you use your machine to first detect only cans and then only quarters.