New Heat Rate Meter Based on Frequency Grading

We describe a wide-range (15-1000 bpm) and high-resolution (1 bpm) heart rate meter whose design is based on the automatic grading of the clock frequency. Each pulse resets the counter that starts counting at high frequency (16 667 Hz); if no pulse arrives within a preselected interval, the clock frequency is reduced by a factor of 4. This procedure may be repeated one or more times, depending on the pulse delay, and results in a step-like decrement of the clock frequency. This allows a very efficient use of the memory capabilities of two suitably programmed EPROM's.