Measuring Liquid Density with a Tuning-Fork Transducer

This paper describes a microcomputer-controlled measurement system for continuous measurement of the density of a streaming liquid. The system utilizes a transducer that resembles a hollow tuning fork filled with liquid. The resonant frequency of the fundamental mode of this device is a function of the liquid density. Piezoelectric means are used to force the device to oscillate and to register the oscillation. A microcomputer controls a frequency sweep, detects the resonant frequency, and converts the frequency to density. Accuracies on the order of 0.05 percent have been recorded in laboratory tests. The system is suitable for industrial applications.