Operating Principles - Xylem MJK Oxix Installation And User Manual

Dissolved Oxygen Transmitter

Operating Principles

The MJK Oxix Dissolved Oxygen Transmitter is designed for measuring the
®
oxygen contents in open tanks exposed to sunlight, wells and closed contain-
ers.
The Oxix sensor function is based on the fluorescence principle and does
®
not consume oxygen like membrane-type sensors. It is rugged and designed
to handle tough applications.
Light pulses with a wavelength of 475 nm are transmitted to a ruthenium
compound immobilized in a sol-gel matrix.
The ruthenium absorbs the light energy by changing the outer electron's ener-
gy level. The unstable electron then collapses and returns back to its original
energy state and at the same time emits the surplus energy as a photon with
a wavelength of 600 nm. This process is also refered to as fluorescing.
When the intensity of the transmitted light pulses is tightly controlled, the
amount of fluorescing is predictable and repeatable.
If free oxygen molecules are present, the photon energy is absorbed by the
oxygen molecules without any light emission, and the amount of fluorescing is
consequently reduced (also refered to as fluorescence quenching).
It is therefore possible to determine the amount of dissolved oxygen by meas-
uring the amount of fluorescence quenching (light intensity).
GB Oxix Manual 1209 10
FW: 841013-009, 846001-002, 841513-009