®
Advanced Water Quality Sensor
Dissolved Oxygen
6
012-14325A
If these steps fail to improve the response of the electrode, replace it.
Storage
Store the pH electrode in the included electrode storage bottle with one of the follow-
ing solutions. (Never store the electrode in distilled water.)
•
Short-term
(up to one week): pH 4 buffer solution or tap water.
•
Long-term
(over one week): 4 molar KCl solution (included with the electrode).
Dissolved Oxygen
The Optical Dissolved Oxygen Probe is designed to measure the concentration and
the saturation percentage of dissolved oxygen molecules (O
2
) in aqueous solutions.
The Optical Dissolved Oxygen Probe has several advantages when compared to a gal-
vanic (electrochemical) dissolved oxygen sensor. The advantages include:
•
no warm up time
•
no calibration required
•
no filling solution or electrode polishing
•
no flow dependency
The sensing element of the Optical Dissolved Oxygen Probe is called the Sensor Cap.
The sensing element has two layers, The outer layer is a paint that acts as an oxygen
permeable diffusion layer which allows oxygen molecules to pass though while pro-
tecting the dye layer. The sensing layer is an immobilized polystyrene dye layer that
luminesces when excited with light of the correct wavelength. The probe measures
dissolved oxygen by emitting a blue light of the proper wavelength that causes the
dye in the sensing layer to luminesce (glow) a red color. Oxygen dissolved in the sam-
ple being tested continually passes through the diffusion layer to the dye layer, affect-
ing the luminescence lifetime and intensity of the dye. The sensor’s photo-diode
measures the lifetime of the luminescence as it is affected by the oxygen and com-
pares the reading to a reference.
Factors that Affect Dissolved Oxygen Measurement
Factors that affect dissolved oxygen measurement include temperature, barometric
pressure, and salinity.
Temperature: The rate of diffusion of oxygen through the Sensor Cap changes with
temperature (approximately 1.5% per degree celsius). The Optical Dissolved Oxygen
Sensor Cap
Nose-piece,
Optical Dissolved
Oxygen Probe
Diffusion Layer
Sensing Layer
Photo-diode and Light
Emitting Diodes (LED)
NOTE: Do not remove the
Sensor Cap except to replace it.
