The paper presented cumulative statistics of the wavefront parameters of the lightning current measured at the CN Tower in 1999. In 50% of the cases, the maximum current steepness exceeded 15.66 kA/µs, the peak current exceeded 4.88 kA, and the risetime exceeded 693 ns.
It is highiy recommended that the current sensors are placed away from the structural discontinuities of the struck object for the proper measurement of lightning current wavefront parameters and the possible recovery of the original lightning signal.
In order to have a meaningful measurement, the overall risetime of the measuring system must be significantly smaller than the risetime of the captured signal. In the light of the CN Tower lightning data, it is recommended that digitizers with time resolution of 5 ns or better and current sensing device having at most 10 ns risetime be used. The utilization of an optical fiber link with a wide bandwidth is also recommended.
Since the range of variation of the lightning current derivative or the current itself exceeds one order of magnitude, the use of 10-bit digitizers is highly recommended. However, two channels of an 8-bit digitizers can also be used with each channel set at different scales to enhance the vertical resolution