Step 5: Build the circuit.

Picture of Build the circuit.
Cut your PCB to be small enough to fit into the opening, but large enough accomodate the circuit (see secondary picture below).

Once the board is prepared, construct on it the circuit shown below. Note that the copper electrode should be connected to the circuit with shielded wire. The shielding should be connected to ground on the circuit, but not by any means touch the electrode.