Oxygen sensor for indirect calorimetry based on Ruthenium fluorescence quenching

Estimation of the body energy expenditure is a key issue for monitoring and understanding obesity and other nutritional problems. Indirect calorimetry estimation, based on oxygen and carbon dioxide measurements, is the only way to achieve this result. In this paper a compact yet efficient oxygen sensor is presented as a key component for this application. Ruthenium fluorescence is used as sensing element due to the strong quenching effect in presence of oxygen. An FPGA-based TDC and data retriever have been implemented granting a high degree of freedom in terms of tunability and resolution.