What term defines two or more coils electrically connected in opposition during testing?

The term that defines two or more coils electrically connected in opposition during testing is "differential." In a differential electromagnetic testing arrangement, the coils are positioned in such a way that they respond to changes in the electromagnetic field created by the test specimen. By connecting the coils in opposition, any uniform fields or noise are effectively canceled out, allowing for enhanced detection of variations or anomalies within the material being tested. This method is particularly advantageous as it increases the sensitivity of the detection system for locating discontinuities or flaws in conductive materials.

The other terms do not accurately describe this setup. "Absolute" typically refers to measurements taken from a fixed reference point without accounting for opposing signals. "Laminar" generally relates to flow dynamics and is not applicable in the context of electromagnetic testing. "Flying probes" refers to a specific testing technique where probes move across a circuit board to test connections, which does not align with the concept of coils connected in opposition.