Concentration measurement of opaque dye solution using a non-contact fiber displacement sensor

Abstract

This paper reported the experimental and theoretical analysis of a non-contact fiber optics displacement sensor for the concentration measurement of opaque dye solution. This sensor was able to detect the concentration without having to dilute the opaque solution. Brilliant Blue FCF dye was used to demonstrate the sensor. The displacement curves of dye solutions with various concentrations were taken using a white light source and a spectrometer as the detectors. The cumulative reflected powers (CRP) of the samples at various wavelengths were determined, and the simulated data were also in agreement. A unique transition wavelength was observed at 613.5 nm when the samples’ CRP curve was compared with the water data. The sensing parameter was based on the total positive differences in the CRP results in a highly linear relationship over the dye concentration of 0.01 to 0.1 M. The sensitivity was measured at a.u./M and the resolution was 2.0 mM. The proposed sensor had consistent performance, and the results were highly repeatable measurement with small variances.