FDO : Fluorescence D.O. Measuring – What exactly does this mean?
The optical principle:
With the optical method a fluorescent dye is stimulated in the membrane of the FDO® 700 IQ 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. In principle the measurement of the fluorescent signal come back to a highly precise time measurement.
• No incident flow needed
• Insensitive against bubbles
• Low costs of ownership
D.O. sensors of the first generation had a handful of technical issues to cope with.
• Sensor drift through watering impact of the membrane
• Wearing of cye layer in the sensor through highly energetic blue light
• Sensitivity of sensor towards air bubbles
Through consequent development work the difficulties appearing with the first generation sensors could successfully be eliminated with the second generation models.
1 IQMC Technology
Each cap is individually factory calibrated. The calibration data are permanently stored on a chip which is installed in the membrane cap.
2 EPRS = Equal Path Reference System
Measuring and reference path as well as optical components are identically designed with this sensor. Natural ageing processes of the optical components can therefore be compensated by the reference path and accordingly compensated in the measuring path. This causes a continuous high performance of the sensor.
3 GLT = Green-light Technology
By stimulating the fluorescent reaction in the membrane with low energetic green-light, a bleaching of the fluorescent dye in the sensor membrane is avoided. This leads to a membrane lifetime of min. 2 years.
4 45° Technology
The membrane SC-FDO® has a horizontal slope of 45°. A congestion of air bubbles in front of the membrane, as
experienced with the first-generation of optical D.O. sensors, is therefore avoided.
The optical measuring technology is based on a attenuated fluorescent signal in a defined time frame. The D.O. measuring is more or less a highly precision time measurement. In order to process this time measurement as precise as possible, the sensor optics are calibrated to the speed of light. This natural constant “c” is defined as the time that a light beam needs to go from point A to point B – in short: the speed of light. The sensor is precisely calibrated against a physical constant.
O2 concentration 0 ... 20.00 mg/l
(0 ... 20.00 ppm)
O2 saturation 0 ... 200.0 %
201 650 FDO® 700 IQ Digital calibration free optical D.O. sensor (universal use). Optimized for monitoring/controlling O2 input in wastewater treatment plants, for use with IQ SENSOR NET. Factory calibrated system composed of sensor FDO® 700 IQ and membrane cap SC-FDO® 700, without connection cable (SACIQ order separately)
201 660 FDO® 701 IQ New Digital calibration free optical D.O. sensor with fast response time (universal use). Optimized for monitoring/controlling O2 input in waste water treatment plants, for use with IQ SENSOR NET. Factory calibrated system composed of sensor FDO® 700 IQ and membrane cap SC-FDO® 701, without connection cable (SACIQ order separately).
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