Implementing the RTD fluxgate magnetometer for measurements of kinematic viscosity

In this paper a novel application for the Residence Times Difference (RTD) fluxgate is proposed: measurement of the kinematic viscosity of fluids. The measurement of kinematic viscosity is possible, indirectly, through the magnetic tracking of an iron ball falling down within a burette filled with a fluid ("falling body" method). In general, the "falling body" viscometer usually needs at least two sensors and a timer to record the falling time of the object. Instead, in the system proposed, only one fluxgate is needed and the synchronization with an external timer is also avoided. Five fluids, comprising glycerol and a sanitizer gel in different percentages, have been used as targets. At first, two configurations of RTD fluxgate (the straight fluxgate and the ring fluxgate) have been tested in parallel with only the gel as fluid. The ring configuration, at its center, shows a response far better than the straight configuration. Then, the RTD ring fluxgate was calibrated by varying the fluid in the burette. The calibration diagram clearly demonstrates that the width of the RTD signal is directly proportional to the kinematic viscosity of the fluid in the burette. The variation of the width is observed also without the averaging of the RTD. This novel application opens the perspective of RTD fluxgate as a multi-sensing device with applications toward wider contactless sensing strategies, affording the possibility of also using the fluxgate in previously tested applications, but within a dynamic framework.