TD 269 OPERATING MANUAL
OXYGEN OPTODE 4330, 4831, 4835
June 2017
page 47 of 93
The relationship between the O
2
concentration and the luminescence decay time can be described by the
Stern-Volmer equation:4
[ ]
−
=
1
1
0
2
τ
τ
SV
K
O
where:
τ
= decay time
τ
0
= decay time in the absence of O
2
K
SV
= Stern-Volmer constant (the quenching efficiency)
In order to measure this luminescence decay time, the sensing foil is excited with a blue-green light
modulated at 5 kHz.
The decay time is a function of the phase of the received signal.
In the Oxygen Optode the relationship between the phase and the O
2
-concentration is used directly,
without calculating the decay time.
Figure A 3 shows a typical relationship between the phase measurement and O
2
concentration.
Figure A 3 Typical Phase/O
2
response
400
300
200
100
0
10
20
30
40
50
60
70
O
2
C
onc
ent
ra
tion [
µM
]
Phase shift [degrees]
