Examining Objects with Electric Fields

An apparatus for examining objects using electric fields, comprising:

• a first set of electrodes;
• an energising circuit for energising a selected one of said electrodes as a transmitter;
• a monitoring circuit for monitoring a selected one of said electrodes as a receiver, such that an energised transmitter electrode and a monitored receiver electrode establish a coupled pair of capacitively coupled electrodes during a coupling operation;
• and
• a processor, wherein said processor is configured to:
• select two of said electrodes separated by a first distance as a first coupled pair during a first coupling operation;
• and
• select two of said electrodes separated by a second distance as a second coupled pair during a second coupling operation;
• wherein:
• said second distance is larger than said first distance;
• and
• said first coupled pair and said second coupled pair both include a first electrode in common.