Design of a Tuning-fork Liquid Densitymeter
Amod Kumar, Shashi Bhushan Sharma · IETE Technical Review · 2004
A New and efficient method of measuring on-line density of a process liquid has been developed. The sensor is a piezoelectrically excited vibrating tuning fork structure whose vibration amplitude is maximum at its resonance frequency. This resonance frequency is a function of the mass or density of the surrounding medium in which fork is put. The tuning fork is excited at frequencies sweeping from 800 Hz to 1 kHz in steps of about 5 Hz. The resonant amplitude is sensed by another piezoelectric crystal mounted on the other tine of fork. Once resonant frequency is crudely estimated, the step size is reduced to about 2 Hz and a short sweep cycle allowed to run around the resonant frequency to accurately determine the resonance frequency. A microcontroller based electronic circuit controls and measures the resonant frequency and converts it into density. The instrument has been calibrated in the laboratory.