FDO 700 IQ from WTW – The Next Generation Optical D.O. Sensor

Optical D.O. measurement based on dye luminescence is strongly promoted in these days. The manufacturers of such instruments claim far superior performance compared to conventional electrochemical sensors. In theory, the functional principle of the optical D.O. measurement confirms this superiority. However, practical realisation and application does set certain limits and, as usual, further technical development is needed to bring theory and practice to accordance.

WTW’s FDO 700 IQ D.O. sensor belongs to a new generation of these sensors that eliminate the drawbacks of the former ones.

• High accuracy right from the start
• Utmost stability over a long timespan
• Minimum maintenance effort

This is achieved by entirely new technologies:

• Intelligent Membrane with IQMC technology
• Soft Green Light Technology
• (C2) calibrated optics
• EPRS reference procedure

What does IQMC mean?

'Intelligent (IQ) Membrane Calibration' means that for each membrane individual calibration values are determinated in the manufacturing process and stored in a chip on the membrane. These calibration data characterize the whole membrane properties. Upon application of the membrane, the sensor automatically reads out the values, thus guaranteeing the utmost calibration accuracy even after a membrane exchange. Manual re-calibration is not necessary.

'Soft Green Light Technology'

In contrast to ultraviolet light, green light is 'gentle light' and avoids premature bleaching of the dye coating. The result is an extreme long-term stability, meaning utmost accuracy and low drift over a long timespan.

What are (C2) calibrated optics?

The optics of each sensor are calibrated according to the Coherent Calibration (C2) technique during manufacture. The transit time of a light beam on a reference path and hence the physical constant c is used for calibration. The accuracy achieved surpasses that of any other method. The calibration data are stored in the sensor for lifetime.

What is the EPRS reference procedure?

EPRS means Equal Path Reference System, i.e. the maximum accordance of excitation and reference beam causes the lowest possible drift of the optical system over the whole lifespan.