Flow sensor for field measurement of viscous liquid usage for consumer studies

The usage of household liquids such as detergent or shampoo is a relevant parameter in customer research. It has to be measured in a real environment to eliminate effects of staged studies. We present a 3D-printed sensor usable for both flow and derived mass measurements for such high viscous liquids. It can handle pulsating flows and has negligible influence on typical user´s behavior. The sensor is a variable-area sensor with a spring-loaded float to ensure operation in all positions. Displacement is measured by a hall sensor and magnet inside the float. Because of the temperature dependence of the liquid´s viscosity, a temperature sensor and a look-up-table are employed to derive mass measures from displacement measures. System size is Ø20 mm × 120 mm; it fits in a commercially available detergent bottle. Readout is realized by an IrDA-interface, a LiPo battery ensures six month operation. The sensor exhibits an overall accuracy of -0.36 % and a lower precision of 10.09 % for a nominal range of 1 to 6 g of fluid.