Simultaneous sensing of dissolved oxygen and probe temperature using a ruby insert and compact photon counting receiver

Description/Abstract

We present a new sensor capable of real-time simultaneous determination of dissolved oxygen andtemperature sensor. The measurements are achieved by essentially simultaneous interrogation of fluorescence
lifetime of both an oxygen sensing Ru²⁺ pO₂ sensor membrane impregnated in silicone, and
a Cr³⁺-doped sapphire crystal (Ruby). The presence of the ruby crystal provides several advantages
<p>1. It acts as a thermal sensor at the probe tip, that is illuminated by the same LED as the Ru²⁺ sensing layer.
<p>2. As the ruby crystal is mounted at the distal end of the optical fibre probe, it provides a reference signal to
indicate mechanical damage or membrane detachment problems.
<p>3. By providing a reasonably constant fluorescence intensity, more significant, yet gradual changes in
fluorescence light output from the membrane (e.g. due to photo-degradation) may be detected.