Engine frequency/speed measuring appliance

The utility model relates to a generator frequency/ rotary speed measuring appliance which comprises a sampling circuit 1, a timer 2, a clock reference circuit 3, a counter 4, an arithmetic device 6 and a display 5, wherein the counter 4 is used for counting the value of the coincidence relation of standard time clock pulsed signals and sampling pulse signals in a turn-on period controlled by the timer 2, and the value is input in the arithmetic device 6; after the value is calculated, rotary speed or frequency value which can be directly displayed in the display is obtained. The sampling circuit 1 uses AC electrical waves of a generator as sampling objects. When the sampling pulse signals are sent, long integer signals are corresponding to a signaling conversion circuit which converts voltage signals into pulsed signals in the AC electrical wave period of the generator.