Remote sensor telemetering system

Abstract

A telemetering system for remotely measuring a physical parameter of an object such as a human or animal includes a sensor device affixed to the object including a tuned circuit and a parameter sensitive device coupled for altering the figure of merit of energy storage (Q) of the tuned circuit in response to variations in the physical parameter, and an indicator unit for transmitting a signal to intermittently ring or energize the tuned circuit with a burst of oscillating electromagnetic energy and sense the resultant reradiated ring signal generated by the tuned circuit. The indicator unit measures the rate of decay of the sensed reradiated ring signal after the end of each transmitted energy burst as a measure of the Q of the tuned circuit. The indicator unit includes a microprocessor which generates a measure of the rate of decay and then computes the measure of the physical parameter according to a prestored functional relationship between the physical parameter measure and the decay rate of sensed ring signal. The computed measure is then displayed in a display device. A phase locked loop circuit in the indicator unit is coupled to alter the phase and hence the frequency of the transmitted signal to be in phase with the resonant frequency of the tuned circuit. The decay rate may be measured by generating a ratio of peak voltage values sampled at two different but predefined times after the sensed ring signal begins decaying.