Handy Kitchen Liquid Food Viscometer Using a DC Motor as Actuator and Sensor

Liquid food can likely cause accidental ingestion in patients with dysphagia. This study proposes a handheld stirrer-type rotational viscometer that can be used in the kitchen or at meals for dysphagia. A novel rotational viscometer is proposed considering that the rotation speed of the handheld stirrer is inversely proportional to the viscosity of the fluids to be stirred. We adopt the sensorless control strategy. We use a small brush-type DC motor, which functions as a rotary actuator and a rotational speed sensor to realize the proposed device. Because the proposed viscometer is used in the aforementioned fields, it must be compact, handy, simple in structure, and low-cost. We apply the proposed viscometer to fluids with viscosities ranging from 5000 to 54000 mPa $\cdot \text{s}$ for testing, using a cylindrical rotor with a length of 15 mm and diameter of 10 mm. The repeatability and linearity as a measurement instrument evaluated by the ASTM standards E3116-18 are less than 5% and 4% for the aforementioned fluids under the temperature of 11 °C, respectively. Because the thickness of liquid food is classified into only three categories (mildly, moderately, and extremely thick), the accuracy of this method is sufficient for the measurement.