A new low-maintenance, low-cost optical system to measure low level oxygen concentrations by using avalanche photodiode (APD)

In this paper, a very simple and low-cost photodetection system is presented which can be used for measuring very low oxygen concentration in gaseous medium based on the phosphorescence lifetime of Al-Ferron in a sol-gel probe. A similar system has been presented by other authors but the most innovative aspect in this work is the use of an Avalanche Photodiode (APD). The APD has several important advantages over photomultiplier tubes (PMTs) such as a lower device size, low cost and less critical power supply requirements. The APD has a good photosensitivity and low dark current, sufficient characteristics for measuring phosphorescence