Inline fabric conductivity measurement

A method for non-destructive, inline, multi-channel fabric conductivity measurement, the method comprising:

• a processor-based controller selecting a first microwave frequency and a first one of a plurality of transmit microwave horns;
• transmitting first microwave energy from the first transmit microwave horn at the first microwave frequency, through a conductive fabric material moving on a production line;
• receiving the transmitted first microwave energy with a first receive microwave horn placed to be paired with the first transmit microwave horn as being opposed to the first transmit microwave horn on an opposite side of the material from the first transmit microwave horn, the first transmit and receive microwave horns forming a first horn pair;
• transducing the received first microwave energy and storing, by the processor-based controller, a first representation of the transduced received microwave energy to a computer-readable memory;
• the processor-based controller selecting a second microwave frequency, either the same as or different from the first microwave frequency, and a second one of a plurality of transmit microwave horns, different from the first one of the plurality of transmit microwave horns;
• transmitting second microwave energy from the second transmit microwave horn at the second microwave frequency, through the conductive fabric material moving on the production line;
• receiving the transmitted second microwave energy with a second receive microwave horn placed to be paired with the second transmit microwave horn as being opposed to the second transmit microwave horn on the opposite side of the material from the second transmit microwave horn, the second transmit and receive microwave horns forming a second horn pair;
• transducing the received second microwave energy and storing, by the processor-based controller, a second representation of the transduced received second microwave energy to the computer-readable memory.

A method of identifying a source of a defect in a manufacture of conductive fabric, the method comprising:

• collecting and storing a first set of measurement data characterizing respective conductivities and respective anisotropies of a plurality of locations on a sheet of conductive fabric greater than one hundred feet in length during a first phase of manufacture of the sheet, the measurement data based on detected microwave transmittance between a plurality of microwave transmit/receive horn pairs, each horn pair comprising a transmit horn and a receive horn positioned to oppose each other on opposite sides of the sheet;
• collecting and storing a second set of measurement data characterizing respective conductivities and respective anisotropies of the plurality of locations on the sheet during a second phase of manufacture of the sheet;
• determining at least one defect in the sheet based on at least one of the first or second measurement data sets;
• identifying whether the at least one defect was present in the first phase, the second phase, or both, based on a comparison of the first and second measurement data sets.