|Figure 1: An example|
of a GFCI
Because the 60-Hz cycle is the time when a current is potentially flowing through someone's body on its way to ground, getting a GFCI device certified requires that this period is short enough to ensure that a short circuit is not a killer.
|Figure 2: IEEE definitions of a standard pulse|
|Figure 3: An example of timing measurement|
using IEEE pulse parameters
The problem is complicated further by the fact that burst lengths vary from acquisition to acquisition, as does the exact size and shape of the non-integer portion. One might use cursors to measure burst length, but doing so would require the user to manually reposition the cursors for each varying pulse length. And, suppose the pulse has a false starting edge? Misplacing the cursors in such a case will return an incorrect measurement.
|Figure 4: Parameter scripting automates determination|
of the burst's start and end positions to 1-ns resolution
As a side note, the determination of the burst duration to such fine resolution demands use of an oscilloscope with 12-bit ADCs. Unfortunately, the quantization noise inherent to 8-bit oscilloscopes makes it impossible to so accurately place the start and stop markers.