This device measures charge by accumulating current measurements made at one second intervals, and moving the hands of the clock for increments of charge. There are two ranges, selected by a jumper which inserts an additional shunt resistor in parallel. The lower range of 0-125 MA moves the hands 1 minute for each 1 milliampere-hour, the high range of 0-750 MA has 5 MAH increments. It also measures voltage 0-20V. See my website for details