L uminescence D issolved O xygen an optical and unique way (patent pending) of measuring Dissolved Oxygen

1. Lange LDO™Sensor What does LDO means? • LuminescenceDissolvedOxygen • an optical and unique way (patent pending) of measuring Dissolved Oxygen • eliminates nearly all disadvantages of traditional electro chemical DO measurement

2. Sensor body Sensor cap Luminophor Photo diode red LED blue LED Lange LDO™Sensor How does it look like?

3. Sensor Sensor- cap Luminescence indicator- molekules Lange LDO™Sensor How does it works? • The sensorcap is coated with a luminescent polymer. • For the measurement the blue LED emits a pulse of light. • This passes through the transparent carrier material and transfers part of its radiation energy to this material. • Electrons from the luminophore are in this way raised from their initial energy state to a higher energy level.

4. Sensor Sensor- cap Luminescence indicator- molekules Lange LDO™Sensor How does it works? • The electrons return to the initial state via a number of intermediate levels (within ms) • The energy difference is emitted as a red radiation. • This light is detected by a photo diode.

5. Sensor Membrane Incident blue light Emitted red light Oxygen from sample Lange LDO™Sensor How does it works? Photodiode LED Sensor cap with O2-selective fluorescing molecules The intensity of the residual red light is proportional to oxygen concentration

6. Lange LDO™Sensor How does it works? • If oxygen molecules are now in contact with the luminophore, • these are able to absorb the energy of the electrons in higher energy levels • and make it possible for the electrons to return to their initial state without the emission of radiation. • increasing oxygen concentration results in • a reduction of the intensity of the red radiation emitted. • this causes vibrations in the luminophore, result in electrons leaving the higher energy level more quickly • The lifetime of the red radiation emitted is thus shortened.

7. Lange LDO™Sensor How does it works? • Both aspects are covered by the term quenching. • Their effects are shown next page: the pulse of light sent out by the blue LED at time t=0 is incident on the luminophore that then emits red light immediately afterwards. • Maximum intensity (Imax) and the decay time for the red radiation are dependent on the surrounding oxygen concentration (the decay time t is defined here are the time between excitation and reduction in the red radiation to 1/e times the maximum intensity). • Intensity curve for blue radiation producing excitation and red radiation emitted.To determine the oxygen concentration the life t of the red radiation is analysed. In this way the oxygen measurement is reduced to a purely physical measurement of the time.

8. Exitation puls Sensor Emisson profile s Sensor cap t1 Photo Diode without O2 LED LED t2 with O2 Oxygen Lange LDO™Sensor How does it works? Normed Intensity Time [µs] Luminophor

9. Lange LDO™Sensor How does it works? The LDO technology reduces the oxygen measurement to a pure time measuement - the „Lifetime of Luminescense“

10. Sensor Sensor cap Photo Diode LED LED Lange LDO™Sensor How does it works? A red LED is also present in the sensor The red LED acts as an internal standard(or reference) for a comparison to the red light given off by the luminescent coating. Between flashes of the blue LED a red LED of known intensity is flashed on the sensor element.

11. Customer benefitsLange LDO™

12. Key features of Lange LDO™ Sales arguments for Lange LDO™ • No calibration required • Stable measurement results • Independent from flow rate • Reduced cleaning frequency • Low maintenance efforts • Without interference's • No more poisoning of the sensor • Short response time • No polarisation time • Two year warranty on sensor cap

13. No calibration required Sales arguments for Lange LDO™ • Lange LDO™ sensor is very stable as it does not change it’s relevant characteristics ! • No anode to consume and no electrolyte to deplete  extremely stable measurements • Adjustment of the whole optics due to an internal standard (red LED) • Each Lange LDO™ sensor cap is factorycalibrated Background:  With Lange LDO™ the customer has not to calibrate his DO system anymore!

14. Stable measurement results Sales arguments for Lange LDO™ Background: - Lange LDO™ technology means no chemicalinter action between the sample and the sensor element - Constant adjustment of all optical parts due to an internal standard (red LED) With Lange LDO™ the DO measurement results are stable over a longer period of time and thus more reliable

15. Independent from flow rate Sales arguments for Lange LDO™ Background: - Electro chemical DO meters consume Oxygen during the measurement  Constant need for fresh sample and therefore a min. flow rate required - Lange LDO™ doesn’t consume DO. It requires the presence of a representative DO concentration at the sensor element only No flow rate required

16. Reduced cleaning frequency Sales arguments for Lange LDO™ Background: - No DO consumption during the measurement - DO has not to diffuse through a membrane - DO must only be in contact with the luminescent coating on the sensor cap  Dirt has not the same negative influence with the optical method as with the conventional DO sensors

17. Low maintenance efforts Sales arguments for Lange LDO™ Background:  Only a sensor cap has to be exchanged once every two years : screw on / screw off • No membrane to replace • No more stretching of Teflon (very old procedure) and worrying about air bubbles • No electrolyte to foul or poison • No H2S poisoning of the electrolyte • No more punctured membranes • No more electrolyte depletion • No anode or cathode • No more coating of electrodes • No cleaning of anodes

18. Without interference's Sales arguments for Lange LDO™ • Background: - The Lange LDO™ principle is selective to oxygen only.  No interference with pH swings, waste water chemicals or heavy metals like open galvanic cells • Lange LDO™ is superior compared to (self cleaning) open galvanic DO cells as there are no interference’s

19. No more poisoning of the sensor Sales arguments for Lange LDO™ Background: - Lange LDO™ principle is not based on a chemical inter action between the sample and the sensor element - Lange LDO™ has been tested to a broad range of other chemicals. The sensor element is not affected by these (see data sheet)  Lange LDO™ can measure reliable even in difficult applications

20. Short response time Sales arguments for Lange LDO™ Background: - With the optical measuring principle DO only has to be present in front of the sensor element and not to diffuse through a thick (50 µm) Teflon membrane.  Short response time can be programmed (t90 < 30 s) for high dynamic processes

21. No polarization time Sales arguments for Lange LDO™ Background: - Lange LDO™ is based on a new, optical technology. This technology does not need any “warm-up”. It is ready for use immediately.  Switch the instrument on and start measuring!