振動板粘度計の改良について : レオメーター

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The dynamic viscosity of liquid can be measured by inserting an oscillating metal plate into the liquid and measuring its mechanical impedance by an electronic means. The merit of this device is the convenience for the continuous recording of viscosity, but difficulties lie in securing the good stability of apparatus. The main causes are the fluctuaion of gain in electronic circuits, the dissipation of oscillation energy through the support of plate, the time variation of the mechanical damping of metal plate etc. These difficulties are diminished by the adequate device as employing the zero method, but they are principally eliminated by taking the resonance width instead of the resonant amplitude as the measure of viscosity. When the resonance amplitude is employed as the measure of viscosity, the equation connecting the product of density ρ and viscosity η of liquid to the reading of output meter E, which is proportional to the resonance amplitude or velocity of oscillating plate, is ρη=K_1(E_A/E-1)^2 where E_A corresponds to the resonance amplitude or velocity of plate in the air and K_1 is a constant determined by the mechanical design. A mechanical damping Q^<-1> of the oscillating system is expressed by (f_1-f_2)/f_r, where f_r is the frequency at resonance and f_1 and f_2 are the frequencies at which the amplitude of oscillation is 1/√2 times the resonance amplitude. The variation of Q^<-1> can be followed by measuring the resonance frequency width (f_1-f_2) if f_r does not change. When the mechanical damping Q^<-1> is employed as the measure of viscosity the following equation stands, ρη=K_2(Q^<-1>-Q^<-1>_A)^2 where Q^<-1>_A is the mechanical damping of oscillating plate in the air and K_2 is a constant of apparatus. The fluctuation of Q^<-1>_A is so small compared to Q^<-1> that the reproducibility of measurement is improved. The sensitivity of the instrument becomes better in a range of the lower viscosity in the former method, but of the higher viscosity in the latter method. The most sensitive range can be brought into various values of viscosity by the appropriate design of the mechanical impedance of oscillating plate. The determination of frequencies f_1, f_2, and f_r is easily carried out by measuring the phase angle between exciting voltage and receiving voltage of the oscillating system. In the proposed scheme of apparatus, the electric signal comes out from the phase sensitive detector at the phase angle of 45, 90 and 135 degrees, each corresponding to f_2, f_r and f_1 respectively and indicates these frequencies on the recording paper.
社団法人日本材料学会の論文
1959-04-15

振動板粘度計の改良について : レオメーター

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