Clip-on current sensors are equipped with a top-quality metal core which reduces eddy-current loss and allows for accurate measuring results even with the low primary current. Damping diodes integrated into the measurement output of the current transformers (with current output) protect the secondary side against overvoltages that occur if the measuring circuit is interrupted or if the measuring instrument has not been connected. This function is performed by internal load resistors for the current sensor models (with voltage output).