During the summer of 1997,
a noise—protected current derivative measuring system was installed at the Tower. This system features a 6—m, 20—MHz Rogowski coil surrounding the whole steel structure of the Tower at the 509—m AGL and is connected to the recording station via an optical fiber link. The new current sensing system measures a much better signal—to—noise—ratio than the old system because it captures the whole current and utilizes an optical link.