Use of microcontrollers for diver monitoring by underwater acoustic biotelemetry in multipath environments

Biomedical Telemetry (Biotelemetry) is a special facet of bio-instrumentation which provides a means for transmitting physiological or biological information from one site to another. There are numerous situations in which it is desirable to monitor critical physiological reflexes and responses from freely swimming swimmers or divers. The design and implementation of a novel multi-channel digital acoustic biotelemetry system using a single-chip microcontroller is described. It is intended for monitoring the electrocardiogram (ECG), heart rate, breathing rate and depth of a free swimming diver, but the system has a modular design that can be adapted for the transmission of digital data representing any parameter. The use of the microcontroller enables the digital data to be transmitted in a priority interrupt format from each sensor with programmable pulse width timing. A portable receiver contains an identical microcontroller and is designed to scan three crystal-controlled frequencies to provide a logical output for each detected signal. These signals are captured by a portable data logger and interfaced to a computer for further processing. This automated arrangement greatly reduces the probability of data error by increasing immunity to multipath and reverberation effects. [Continues.]