A digital counter/timer is the most reliable and flexible instrument prepared for measuring frequency. Inaccuracy can be reduced down to 1 part in 108, and all frequencies between d.c. and several gigahertz can be measured. The essential component inside a counter/timer device is an oscillator, which provides a very precisely known and stable source frequency, which is typically either 100 kHz or 1 MHz. This is often stated in a temperature-regulated condition within the instrument to guarantee its accuracy. The oscillator output is transformed by a pulse shaper circuit into a series of pulses and applied to an electronic gate. Continuous pulses at the source frequency alternately start and close the gate. The input signal of unknown frequency is similarly transformed into a train of oscillations and applied to the gate. The number of these pulses that get through the gate during the time that it is open during each gate cycle is equivalent to the frequency of the unknown signal.

Digital counter is a LED power meter that can be practiced for counting (amount/length/footage/batch/event/time), measuring (frequency/rotational speed/linear speed/flow) and position control. The various common method is to join a digital counter with a photoelectric sensor or a rotary encoder to form a number counting system. The photoelectric sensor or rotary encoder output signal for adding a number and the digital counter shows the counting number. Another way, after the digital counter SV is set, once the counting number PV reaches SV, the digital counter internal relay will operate and alarm to complete process control.