Transient electromagnetic apparatus with receiver having digitally controlled gain ranging amplifier for detecting irregularities on conductive containers

摘要

A transient electromagnetic apparatus for use in detecting irregularities on conductive walls of containers forms a multichannel distributed system and includes at least one transmitting antenna, at least one transmitter unit, plural receiving antennas, plural receiver units, and a computer for controlling the transmitter and receiver units. The receiver units each include elements that suppress noise in the received signals. Each receiver unit has a preamplifier, first and second low pass Bessel type filters, a gain ranging amplifier, and an A/D converter. The gain ranging amplifier receives feedback from the output of the A/D converter and provides increased small signal resolution. Each receiver unit also rejects common mode noise with a choke and balanced input impedances in the preamplifier. The apparatus allows an arbitrary number of receiving antennas, receiver units, and even transmitting antennas, and transmitting units, so that the apparatus can be con figured to a variety of containers. Each receiver unit has control logic for controlling the electronics therein and memory for storing data for transfer to the computer. The apparatus includes a median filter for filtering out sferics noise.