A miniaturized ultrasonic flowmeter and telemetry transmitter for chronic animal blood flow measurements

An ultrasonic blood flowmeter telemetry system, using only two integrated circuits and one transistor, has been designed for chronic unanesthetized animal studies. Standard components and construction techniques are utilized. The CW Doppler system employs LZT piezoelectric 10 MHZ transmitting and receiving crystals held in a lightweight polystyrene arterial transducer. The audio frequency, FM Doppler signal modulates an FM oscillator-transmitter to produce an FM/FM radio frequency carrier which is transmitted to an FM receiver at a remote location. The transmitted Doppler audio flow signal is demodulated at the receiver by a zero crossing detector. Power consumption is 48 mw. The 12.4 cc package volume can be further reduced for animal implantation.