Frequency output type motion sensor using self-excited potential oscillation

Abstract

A new method for measuring the velocity of a moving fluid around an electrode was proposed. The method measured the frequency of a self-excited potential oscillation of an iron electrode immersed in H 3PO 4–H 2O 2 solutions. The flow in the neighborhood of the electrode, on which transport processes depended, was presumed to change the oscillation frequency. We found that the frequency, f, was proportional to the concentration of the hydrogen peroxide, [H 2O 2], at the phosphoric acid concentration of 0.5 mol/dm 3 f=A[ H 2 O 2]+B (0.8 mol/dm 3≤[ H 2 O 2]≤1.5) where A and B are empirical constants. Both A and B have a linear dependence on the velocity, v, in the two velocity regions 〈 Region I, v=0.0–1.5 mm/ s〉 A=4.6×10 −2+3.1×10 −2v, B=−1.8×10 −2−2.0×10 −2v 〈 Region II , v=2.0–12.0 mm/ s〉 A=9.3×10 −2+2.6×10 −2v, B=−5.0×10 −2−1.4×10 −2v Based on these equations, the velocity of the solution can be determined by the frequency measurement. This meant that the moving velocity of the electrode against the static solution could be determined. In the same sense, the rotation speed of the electrode and the electrode tilt, which affected natural convection around an electrode, could be measured.