CONDUCTANCE MEASURING APPARATUS

摘要

A conductance sensor uses an auto-tuning oscillator to drive a coil inducing eddy currents in a substance to be measured. The auto-tuning oscillator precisely controls the amplitude of oscillations to eliminate amplitude-dependent effects. The coil may be used to sense the presence of a conducting fluid in a nonconducting pipe or the proximity of a metallic object to the coil. The coil may be used in a cardiac or respiratory monitor having a fixed loop conductor. Monitoring changes in the conductivity of a subject provides a measure of cardiac or respiratory motion.