Question

At high frequencies when the sampling interval is too long in a frequency counter _____________

(a) The counter works fine

(b) The counter undercounts the frequency

(c) The measurement is less precise

(d) The counter overflows

This question was posed to me during an interview.

My question comes from Introduction to Hardware Description Language in section Memory Devices of Digital Circuits

Answer 1

Correct option is (d) The counter overflows

Explanation: Let the sampling time be 1 sec. This means the counter will count the number of pulses from the unknown signal for 1sec duration and would display it after 1 sec. thus if the signal is of 800 Hz, at the end of 1 sec, counter would have counted up to 800. Thus, in case of high frequencies and high sampling time, counter might count beyond its limit and overflows.