Sper Scientific 810025R Stopwatch and Countdown Timer Sper Scientific 810025R Stopwatch and Countdown Timer - 100 Hour. The this timer also has a true stopwatch mode with 1/100 second resolution, lap and split with a range of 100 hours. Counts down from 100 hours in 1 second intervals. 1 Count Up Channel - 1 Count Down Channel Range: 100 Hrs Resolution: 1/100 Sec Dimensions: 2-5/8 x 2-3/4 x 3/8"