Appendix 1. The Tech Behind Palintest's Optical Do Measurement System; Principle Of Operation - palintest Macro 900 Operation Manual

Macro 900 Operation Manual V3
21. Appendix 1. The Tech Behind Palintest's Optical DO Measurement
System

21.1. Principle of Operation

The Palintest Micro 800 Optical DO Meter measurement system works on the
principle of Dynamic Luminescence Quenching. A gas-permeable chemical
known as a luminophore is excited with short bursts of blue light, which causes
molecules in the luminophore to emit red photons. The presence of oxygen in
contact with the luminophore causes the emission of the red photons to be
quenched or delayed. By measuring the delay of the returned red photons with
respect to the blue excitation, it is possible to determine the level of dissolved
oxygen 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 Sensor
Module contains blue excitation and red reference LEDs, optical filters, a photon
detector, temperature sensor, driver circuitry and high gain amplification
circuitry.
The Optical DO Sensor Module
The incredibly small size of the Sensor Module allows it to fit comfortably into
the end of a standard 12mm diameter DO electrode in place of a traditional
Clark Cell. The addition of a replaceable cap containing a lens coated with the
luminophore material completes the DO section of the electrode.
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