Viscosity sensor for nursing care meal using piezoelectric resonator in radial mode

A simple method of viscosity measurement is useful for cooking nursing care meal requiring suitable viscosity for each patients' swallow ability. The purpose of this study is the viscosity measurement for controlling viscosity without protruding any sensor into vessel. Proposed sensor consists of a radial mode piezoelectric resonator embedded in vessel bottom. Electrical impedance of the resonator was measured to obtain equivalent circuit parameters. As a result, the change of the equivalent capacitance linearly responds to the viscosity. Ratio of root mean square errors of estimated viscosity against viscosity of each samples were less than 25 % in the range of 42-229 mPa·s.