| 摘要 |
<p>Pulse frequency meter comprises a pressurisable cuff in which is inserted a microphone which picks up Korotkoff sounds occurring on pressure reduction, to provide a pulse frequency indication from the time sequence of these sounds. A comparator converts the amplified sounds to rectangular pulses each of which is converted by a monostable trigger circuit to a measuring pulse of constant amplitude and duration. For a given time, these measuring pulses are transmitted to an integrator which adds them up to form a measuring voltage. The amplitude and duration of the pulses, and the measuring time, are such that the measuring voltage is proportional to the number of pulses per min., and this voltage controls an indicator.</p> |
