Multiplexing
Multiplexing is the process by which multiple analog message signals are combined into one digital signal on a shared medium. When eddy current array data is multiplexed, the individual eddy current coils are excited at different times, allowing the system to excite all of the coils in the probe without ever exciting any two adjacent coils at the same time. An undesirable effect known as mutual inductance (magnetic coupling between coils in close proximity) is minimized with the use of an internal multiplexing system to carefully program the exact time that each coil is excited to transmit its eddy current signal. The signals are then reassembled before being displayed as an image. In addition to the enhanced imaging capabilities of multiplexed data, multiplexing allows any individual coil (data) channel to be analyzed after inspection. Multiplexing allows an increased channel resolution, increased coil sensitivity (through the reduction of mutual inductance), and a reduced noise level. This ultimately leads to an improved signal-to-noise ratio.
Mutual Inductance is avoided by multiplexing
