Zebra-Tech Ltd
D-OptoLogger Operation Manual
3
1 Introduction
The D-Opto Logger is a fully self contained dissolved oxygen logger,
incorporating a DO sensor, battery, and low power data logger in a rugged
compact underwater housing.
The D-Opto Logger uses a field-proven solid-state optical sensing system to
measure dissolved oxygen that is highly stable over long periods of time, even in
harsh conditions. The data is stored onboard in non-volatile memory. The D-Opto
Logger is setup, and data offloaded using simple Windows based software,
supplied with the instrument.
1.1 Optical Sensor Technology
Unlike conventional dissolved oxygen sensors, the D-Opto Logger sensing
element utilises fluorescence to measure dissolved oxygen. The basic principle
involves subjecting a fluorescing compound (ruthenium) to a fixed wavelength of
light. When the light source is removed, the compound emits a fluorescence, the
intensity of which is dependent on the oxygen levels present in the surrounding
water. An extremely stable electronic circuit has been designed to firstly excite
the ruthenium, and then measure the intensity of the resulting fluorescence.
Therefore using this circuitry, the D-Opto Logger should provide accurate
dissolved oxygen measurements over long periods of time (many months)
without re-calibration.
Unlike conventional polarographic dissolved oxygen sensors, the optical method
does not consume oxygen. Consequently the measurement of dissolved oxygen
by the D-Opto Logger is unaffected by water movement. Similarly the D-Opto
Logger does not utilise a membrane or any other consumables, thus minimising
servicing requirements.
