Abstract: Upon depression of a number key, the timer memory corresponding thereto is started to be in its counting operation state, and when the number is depressed again, the timer memory stops its counting operation. When a relative difference key is depressed, a maximum (or minimum) value is selected from the count contents of respective timer memories and then, when the relative difference key is depressed repeatedly, a difference between the selected value and each of the other count contents in a decreasing (or increasing) order, the number of the number key corresponding to the count contents and its ranking are displayed on a display unit upon each depression of the relative difference key. With one instrument, it is possible to obtain a plurality of timer operations, the ranking of the measured results and their relative differences.