Real Time Process Monitoring of Chemical Parameters using Miniaturized Spectral Sensors: Application to the Energy and Agricultural Fields

The need to monitor processes in real-time is creating a growing demand for new simple and miniaturized analytical instrumentation capable to operate directly in the field. In this context, spectral sensors can play a key role due to their robustness and low cost. Among the diversity of spectral sensing technology currently available, LED-photodetector (LED-PD) spectral sensors are particularly suited for the real-time monitoring in field environments. This suitability relies on its low, compactness, low-power operation, and mechanic robustness.
Hence, this communication will discuss the distinct aspects of the architecture of the instrument, namely the system integration of the optical components (LEDs, photodetectors, optical filters) with the control and readout electronics for real-time measurements. Both commercially available and customized sensors will be considered.
We will also consider two different application scenarios for these integrated optical platforms: (I) the analysis of dissolved gases in transformer oils, and (ii) the analysis of chemical parameters of grape ripening. In the first case, we will focus on the challenge of measuring the gas content (CO2 and CH4) in the headspace of the sample using a combination of IR light source and a photodiode with an optical filter through absorbance. In the second case, we will describe a reflectance measurement of the grape berry based on an array of four Vis/NIR LEDs and four PDs that can provide information about three chemical parameters grape ripening (Brix, Total Acidity, and pH). Additionally, we will also discuss the data pipeline, with a particular emphasis on data transmission (Internet of Things framework) and calibration strategies.