抄録
Characteristics of fiber optic concentration sensor, having advantages such as explosion-proof, applicability to both electrolyte and nonelectrolyte solutions, are investigated by the experiment and 2-dimensional waveguide model. Investigation shows the sensitivity is considerably increased by forming the sensor shape as the figure of 8 and further indicates the mathematical relation between the curvature of the 8-shaped sensor giving the highest sensitivity and the refractive index of the solution under measurement. This new type of sensor, made of fused silica with 1.5mm dia. and 7∼10mm radius curvature, has the resolution of the order of 0.1wt% in water solution.
In case of on-line application, it is required to correct errors automatically caused by temperature change of the solution and the contamination of the sensor. This requirement has been resolved by the development of the sampling apparatus equipped with the automatic rinsing and calibration using a standard solution. This 8-shaped sensor is successfully applied to the electric tinning plant as the tin-ion concentration meter, showing the accuracy of 2σ=0.9g/l.
