  This contribution presents a novel bunch current measurement system based on
an ultra-fast photodetector and a high-speed digitizer at Hefei Light Source II
(HLS II). In order to achieve bunch-by-bunch resolution, the sampling rate of
the system is nearly 225 GS/s via a dedicated equivalent sampling algorithm.
According to preliminary tests of daily operation mode and single-bunch mode,
the root-mean-square (rms) of current relative error distribution is 1.03%,
which illustrates the new system satisfies requirements for high-precision
bunch current measurement. In addition, experiment results of "HLS" Morse code
fill pattern mode demonstrate this system also could be a convenient and robust
tool for beam top-up mode in the future.
