A miniaturised radio telemetry two channel ultrasonic cardiac dimension gauge

A two-channel ultrasonic cardiac dimension gauge telemetry system developed for chronic unanesthetized animal studies is described. The system consists of dual ultrasonic transit time distance measurement circuits and a time-multiplexed FM transmitter. The system employs implantable 5-MHz lead zirconate titanate piezoelectric transmitting and receiving crystals for measurements at 2-22.5 mm. The system is designed with six standard low power ICs and three transistors. Power consumption is 40.8 mW (6.8 mA, 6 V). The 35-cm/sup 3/ circuit weighs 40 gms.<
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