Patent ID: 6044694
Filing Date: 2000-04-04
Classification: B41J,G01F,G01N

Abstract:
A method of monitoring liquid viscosity to maintain the level of a liquid contained in a vessel comprising the steps of:(a) locating at least the vibrating portion of a piezoelectric bender in said vessel containing said liquid;(b) applying a stimulation voltage to said bender at an amplitude and frequency to cause the bender to resonate;(c) varying said stimulation voltage frequency as a function of said output voltage frequency to maintain said bender at resonance;(d) monitoring an output voltage from said bender, the amplitude of said output voltage varying as an inverse function of the liquid viscosity, whereby an increase in liquid viscosity produces a decrease in output voltage amplitude and vice-versa;(e) detecting when the output voltage amplitude signals a change in viscosity indicating that the bender is no longer in contact with said liquid; and(f) automatically replenishing the liquid in said vessel when the liquid is no longer in contact with said bender.