ULTRASONIC WAVE BLOOD FLOW METER

摘要

An ultrasonic wave blood flow meter comprises a probe which sends to and receives an ultrasonic wave reflected with Doppler effect from the blood flow, a detecting circuit for converting a frequency variation of the received reflected wave into a first signal whose amplitude varies with frequency and a second signal whose amplitude is kept constant, and first and second effective-value detecting circuits for obtaining d.c. components of the first and second signals. A level discrimination circuit is further provided for discriminating the level of the d.c. component detected by the second effective-value detecting circuit. First and second sensitivity-variable amplifiers are also provided for varying their sensitivities in accordance with the result of the level discrimination circuit. A dividing circuit divides the d.c. component amplified by the first sensitivity-variable amplifier by the d.c. component amplified by the second sensitivity-variable amplifier, and a voltage hold circuit holds the output of the dividing circuit in accordance with the discrimination result of the level discrimination circuit.