Macro 900 Operation Manual V3© 2013 Palintest Ltd. www.palintest.com Page 133 of 14721. Appendix 1. The Tech Behind Palintest’s Optical DO MeasurementSystem21.1. Principle of OperationThe Palintest Micro 800 Optical DO Meter measurement system works on theprinciple of Dynamic Luminescence Quenching. A gas-permeable chemicalknown as a luminophore is excited with short bursts of blue light, which causesmolecules in the luminophore to emit red photons. The presence of oxygen incontact with the luminophore causes the emission of the red photons to bequenched or delayed. By measuring the delay of the returned red photons withrespect to the blue excitation, it is possible to determine the level of dissolvedoxygen present.Whilst this sounds very simple in principle, the optical system and the high-speed electronics required to obtain good accuracy are extremely complex.Housed in a resin filled, marine grade aluminium body that measures just 8mm(0.3”) diameter by 13mm (0.5”) long, the fully waterproof Optical DO SensorModule contains blue excitation and red reference LEDs, optical filters, a photondetector, temperature sensor, driver circuitry and high gain amplificationcircuitry.The Optical DO Sensor ModuleThe incredibly small size of the Sensor Module allows it to fit comfortably intothe end of a standard 12mm diameter DO electrode in place of a traditionalClark Cell. The addition of a replaceable cap containing a lens coated with theluminophore material completes the DO section of the electrode.
