Electrocardiogram using one second measurement period - has VCO in phase-lock loop to check multiplied signal as beats per minute

摘要

To permit the measurement of heart beat rate over periods of the order of a second, but to express the measurement in beats per minute, the detected frequency is multiplied by a factor of about 60. A voltage-controlled oscillator(11) is incorporated in a phase-lock loop. The phase of the oscillator is compared(14) with the heart beats(10) to ensure that the frequency of the oscillator follows that of the heart, while being around 60 times greater. The oscillator output is stored and used to build up a histogram display under the control of a processor.