An Optoelectronic Monitoring System for Aviation Hydraulic Fluids

A non-dispersive infrared (NDIR) sensor system has been designed to monitor the state of contamination and degradation of aviation hydraulic fluids. Core part of this system is a MOEMS subsystem consisting of a micro cuvette, a MEMS thermal IR emitter and a four-channel thermopile array. For ruggedness, this MOEMS subsystem is integrated into a high-pressure resistant metal package. The MOEMS subsystem measures the transparency of the fluid under test at four specifically chosen spectral channels. Three of these channels allow the water content, the total acidity number and the remaining acid scavenger reserve to be monitored. The forth channel serves for calibration and self-test purposes. Fluid monitoring systems of this kind will form key components in an innovative AIRBUS aircraft maintenance system.