This tachometer lets you measure heartbeats, respiratory rates, and other low-frequency events that recur at intervals of 0.33 to 40.96 seconds. The circuit senses the period offm, computes the equivalent pulses per minute, and updates the LCD accordingly. Although the decimal readout equals 60 fm, the circuit doesn`t actually produce a frequency of 60 fm.
The computation involves counting and comparison techniques and takes 0. 33 seconds. The circuit is posted by Ricardo Jimenez at EDN magazine -Design Ideas.