WQ-FDO Optical Dissolved Oxygen Sensor

Methodology – Optical Dissolved Oxygen Sensor

The WQ-FDO Optical Dissolved Oxygen Sensor’s optical measuring technology is based on an attenuated fluorescent signal measured in a defined time frame. A fluorescent dye is stimulated in the optical dissolved oxygen sensor’s membrane by a short wave length light source. By falling back into the passive state, long wave light is emitted, which is recorded as a measurement signal. If oxygen contacts the dye by diffusing through the membrane the period of back scattering light is shortened according to the oxygen concentration of the sample. The optical dissolved oxygen measurement is more or less a highly precision time measurement. In order to process this time measurement as precisely as possible, the optical dissolved oxygen sensor optics are calibrated to the speed of light.

Optical Dissolved Oxygen Sensor Product Applications

• Long term monitoring of dissolved oxygen in streams, rivers and lakes
• Scientific research projects, both long and short term projects
• Water quality monitoring around industrial outfall
• Homeland security
• Thermocline profiling
• Fish farm and aquaculture water quality monitoring
• Wastewater industry
• Food and wine industry

Optical Dissolved Oxygen Sensor Advantages

The WQ-FDO Optical Dissolved Oxygen Sensor has many advantages over traditional DO sensors. Unlike conventional galvanic and polargraphic dissolved oxygen sensors, WQ-FDO optical dissolved oxygen sensors have no consumable cathodes or anodes that require replacement, minimizing servicing requirements. Neither do the optical dissolved oxygen sensors consume oxygen. Consequently the measurement of dissolved oxygen by the optical dissolved oxygen sensor is unaffected by water flow. The WQ-FDO optical dissolved oxygen sensors can even be deployed in stagnate groundwater bores. The WQ-FDO optical dissolved oxygen sensors have extremely stable electronics – a calibration interval of 1 year is typical.

The measuring and reference path optical components are identically designed inside this optical dissolved oxygen sensor. Natural aging processes of the optical dissolved oxygen sensor’s optical components can therefore be compensated by the reference path and accordingly compensated in the measuring path. As a result, the optical dissolved oxygen sensor provides accurate dissolved oxygen measurements over long periods of time without the need for re-calibration. Additionally by stimulating the fluorescent reaction in the membrane with low energetic green-light, the fluorescent dye in the sensor membrane won’t be bleached out.

The WQ-FDO optical dissolved oxygen sensors can be used to monitor dissolved oxygen in almost any liquid, including wines, beer, and milk. The optical dissolved oxygen sensors are not affected by color of the liquid. With the beveled membrane design bubbles or aeration do not affect the optical dissolved oxygen sensor’s measurements. There is no chemical interference from typical wastewater chemicals and the optical dissolved oxygen sensors can withstand harsh wastewater applications.
Global Water’s PC320 Optical Dissolved Oxygen Controller can use the optical dissolved oxygen sensor’s 4-20mA output to control pumps or alarms. In addition Global Water offers the GL500 optical dissolved oxygen data logger which adds recording capabilities and the ability to report DO concentration and saturation measurements from the 4-20mA optical dissolved oxygen sensor. The GL500 optical dissolved data logger connects to the optical dissolved oxygen sensor’s 4-20mA output, along with optional conductivity and barometric pressure sensors, to record highly accurate dissolved oxygen data.