DISCUSSION
The ferrite coil probe was used where the distance to the
appliance was 30 centimeters or greater. The probe is a long,
multilayered cylindrical coil wound on an acrylic bobbin. It
has a high permeability ferrite core and a resistive
termination to provide high sensitivity and a flat frequency
response. The off-axis rejection of this probe is better than
500 to 1, making it highly directional. While more sensitive
and directional than the air core probe, it has less spatial
resolution and tends to measure the average magnetic flux
density over a larger volume. The probe produces output
voltages proportional to the magnetic flux density.