A simple programmable frequency meter for low frequencies with known nominal values

A meter which can be used to measure instantaneously the frequencies of various signals, such as power line frequencies, heart rates, and motor speeds, by only choosing the proper clock and nominal frequencies is described. The technique is based on using an up/down counter operating in the down mode only, resulting in minimum timing signals. Thus the meter is designed with a minimum number of digital integrated circuits. Two frequency meters for heart rate and power line frequency measurements are discussed. A prototype of the proposed meter is built and tested for various frequencies