Simultaneous magnetic actuation and observation with ferromagnetic sensors

Abstract

We present a novel, non-contact, and non-optical approach to actuation and sensing. In the developed method, both functions are based only on the alternating magnetic field and take place simultaneously. The article demonstrates the technique in one of its potential applications, i.e. rheometry. The developed device uses two orthogonal pairs of inductor coils to generate a rotating magnetic field. The field actuates a rotor with an embedded NdFeB ring magnet. The angular displacement is simultaneously monitored with an angular AMR sensor, placed underneath the rotor. The device is used to study aqueous solutions at different concentrations of glycerol (10-95%). The accuracy of the angular sensing is verified using machine vision and pattern recognition, which is a technique widely used in the existing viscometers. A new approach to viscosity probing and phase slipping detection is introduced. So far, in non-contact rotational viscometers the dynamic viscosity was related to a critical frequency, determined by altering the frequency of the rotating magnetic field. However, we propose to alter the magnitude of the field, by changing the current in the inductor coils. The frequency is kept constant and the viscosity is proportional to the amplitude of current, for which the phase slipping occurs. The applied rate of rotation can be optimized for a particular measurement scenario. The results suggest a great potential of the technique in a variety of scenarios. Simultaneous magnetic actuation and sensing enables application in a broad frequency band, from dc to tens of kilohertz. Moreover, the design of a measurement device is simplified, so that its cost can be significantly lower than that of a conventional system. Furthermore, presented method is non-contact, does not require a clear optical path, and could be less susceptible to the environmental conditions (e.g. poor illumination, or full immersion in the studied solution).

Influence of Ruthenium Doping on the Crystal Structure and Magnetic Properties of Pr0.67Ba0.33Mn1–xRuxO3 Manganites

“…Doped perovskite manganite compounds with the general chemical formula A 1−x M x MnO 3 (A = La, Pr, Nd, and M = Ca, Sr, Ba) are gaining increasing attention because the compounds in this family exhibit a colossal magnetoresistance (CMR) effect, metal-to-insulator transition, charge ordering, and phase separation, as well as a remarkable variety of structural, physical, and magnetic properties [1][2][3]. The compounds exhibit a range of structural, electronic, and magnetic phase transitions by substituting different ions at the A or Mn sites.…”

Dual Measurement Mode Rotational Viscometer

“…Our viscometer setup employing simultaneous magnetic actuation and sensing has been published [18]. A permanent ring magnet is attached to the disposable rotor and two pairs of inductor coils act as a stator.…”

“…In order to analyze the viscosity characteristic liquids, the magnitude [18] or the frequency [20] of the external rotating magnetic field is altered, until a sudden change in the rotational response of a probe happens. This occurs when the rotation mode changes from synchronous to asynchronous, causing a fast back and forward motion of the probe [12,15,21].…”

“…That breakdown condition is proportional to the dynamic viscosity of the solution. However, once the inertia of the instrument increases, the accuracy of the measurement decreases for low viscosity solutions [18] limiting the dynamic measurement range of it. The setup was found to provide proper viscosity values from 10 cP to ∼ 400 cP [18].…”

“…In this paper, we demonstrate a significant extension of the viscosity sensing capabilities of the rotational viscometer based on simultaneous magnetic actuation and sensing. Inertia of the instrument limiting the dynamic range in phase slipping detection mode [18] is now used in order to determine the viscosity of the solution through a stress step test and analysis of ringing oscillations.…”