PCS Technical Notes: FL-2, Fluoroprobe, General

Overview of Principle and Operation

The Fluoroprobe is new technology that is changing the way the World measures oxygen. Inside the sensor, a laser light is directed onto a silicon tip impregnated with a special material that fluoresces in the presence of oxygen. The fluorescence is the reflection of light in a different wavelength to the incoming light. The degree of fluorescence changes with the concentration of oxygen. The concentration of light in the different wavelength is a direct measurement of the concentration of oxygen present at the sensor tip.

This new technology provides long term measurement stability never before available with dissolved oxygen measurement. As an optical based measurement there are no electrolyte solutions or membranes to replace and the requirement for routine maintenance is eliminated. The measurement does not consume oxygen and so does not suffer fouling problems, which exist with other oxygen measurements.

Conventional dissolved oxygen measurements drift with time and require regular calibration. The Fluoroprobe’s incredible long-term stability eliminates the requirement of regular calibration. The Fluoroprobe is supplied pre-calibrated and does not even require calibration at the initial installation.

The Fluoroprobe is well established in the USA and has now also been proven in Australia to provide long-term stability and reliability for dissolved oxygen measurement in harsh industrial effluent applications.

As there are no consumable components or routine maintenance requirements with the Fluoroprobe, the overall cost of dissolved oxygen measurement is now substantially lower than ever before. The purchase cost of the Fluoroprobe is higher than the conventional measurements but, without the regular maintenance costs, the Fluoroprobe provides the lowest cost of measurement after around 3 years operation. This lower cost of measurement is not the main benefit of the Fluoroprobe, it's greatest benefit is long-term stability. The measurement stability provides reliability in DO measurement that gives the confidence necessary for high performance closed loop automatic control. It also provides process alarms that can be trusted.

The Fluoroprobe is most commonly connected to a PLC or DCS control system via it's 4-20mA signal and relay outputs. However, it can also operate as a stand alone controller for aeration, without the need for separate control equipment.