Probe multiplexing in eddy current testing means that multiple probes (or multiple test coils) are operated quasi-simultaneously with the same set of test parameters (excitation frequency; amplification, phase and filter settings; thresholds, etc.). Technically speaking, a multiplexer (MUX) is used to quickly sequence through the individual probes. This means that each individual probe is only operated for a short duration.

Multiple probes or array probes can be operated very efficiently this way. To scan a test surface two dimensionally, for example, all that is necessary is to scan it mechanically in one direction. The second dimension is covered by “virtual scanning” via multiplexer (electronic shifting in a fixed time frame).

Probe multiplexing allows considerable time savings compared to the single-probe method. It also allows a considerable reduction in hardware outlay in comparison to conventional testing technology (lower number of testing modules and instruments necessary).

As opposed to simultaneous multi-probe testing there is a reduction of mutual interference (crosstalk). The use of array probes thus allows the testing of relatively large surfaces with high measurement sensitivity and local resolution in the shortest of times.