ABSTRACT
In cases where measurements can be performed from the top surface of the concrete component, the use of larger magnets is feasible.
As a consequence a big electromagnetic unit of 3.50 m length has been developed (Fig. 4). 120 Hallsensors are mounted in six 50 cm long single elements driven extremely near to the testing surface. The robustness of measurement, the resolution of the signal and the speed could be enhanced significantly compared to the previously used rotating system since 2006 (Szielasko et al. 2006).
