Endress+Hauser Memosens COS81D, Руководство по эксплуатации, Страница: 8 / 48

Device description, function Memosens COS81D
8 Hauser
3 Device description, function
3.1 Optical measuring principle
Sensor structure
Oxygen-sensitive molecules (markers) are integrated into the optically active layer
(fluorescence layer).
The fluorescence layer, an optical insulating layer and a cover layer are applied on top of
one another on the carrier. The cover layer is in direct contact with the medium.
The sensor optics are directed at the rear of the carrier and therefore at the fluorescence
layer.
Measurement process (principle of quenching)
If the sensor is immersed in the medium, an equilibrium is very quickly established
between the oxygen partial pressure in both the medium and the fluorescence layer.
1. The sensor optics send orange light pulses to the fluorescence layer.
2. The markers "respond" (fluoresce) with darkred light pulses.
 The decay time and intensity of the response signals are directly dependent on
the oxygen contents and oxygen partial pressure.
If the medium is free from oxygen, the decay time is long and the signal is very intense.
Any oxygen molecules present mask the marker molecules. As a result, the decay time is
shorter and the signals are less intense.
Measurement result
‣
The sensor calculates the measurement result on the basis of the signal intensity and
decay time using the Stern-Volmer equation.
The sensor provides measured values for temperature and partial pressure as well as a raw
measured value. This value corresponds to the fluorescence decay time and is approx.
14 μs in air and approx. 56 μs in oxygen-free media.
For optimum measurement results
1. During calibration, enter the current air pressure at the transmitter.
2. If the measurement is not performed at
Air 100% rh :
Enter the current humidity.
3. In the case of saline media:
Enter the salinity.
4. For measurements in the units %Vol or %SAT:
Also enter the current operating pressure in the measuring mode.
• Operating Instructions for Memosens, BA01245C
For all transmitters, analyzers and samplers in the Liquiline CM44x/P/R, Liquiline
System CA80XX and Liquistation CSFxx product families
• Operating Instructions for Liquiline CM42, BA00381C and BA00382C