A Moisture Detection Sensor for Flour Based on the Gas in Scattering Media Absorption Spectroscopy

Abstract Flour is an essential ingredient in human daily diet, thus it is crucial to measure its moisture content. However, the detection of flour moisture content at present is time-consuming and labor-intensive, which makes it impossible to measure moisture quickly. This study demonstrates the measurement of moisture content in flour via gas in scattering media absorption spectroscopy (GASMAS) technique. A 1392 nm semiconductor laser is utilized as the light source, and a detector consisting of a photodiode and a transimpedance amplifier converts the light into an appropriately amplified signal. The output 2f signal is processed by the demodulation circuit board, and then converted by 16-bit ADC before being input to the STM32F405 for further processing. The equivalent average path length of ten flour samples from same brand and four from different brands are measured by GASMAS technique. Besides, to verify the measurement sensitivity of GASMAS, the equivalent mean path lengths of five flour samples from one brand with varying moisture content are measured. Furthermore, a linear relationship between path length and moisture content are established by least squares curve fitting, corresponds to a correlation coefficient of 0.996. Finally, to validate system accuracy and reliability, five samples with unknown moisture content are measured. Compared to the oven drying method, our method shows a maximum error range of 6.1 % for all samples, and GASMAS provides highly accurate and reliable measurement of water content in flour.