CellOx 325DO ELECTRODES
Galvanicoxygen electrodes for DO meters
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The CellOx 325 DissolvedOxygen (DO) electrodes are easy to use and maintain electrodes for taking DOfield measurements. The DO electrodes are temperature compensated andwaterproof to the IP 68 standard. The DO electrodes have a long workinglife of up to six months from one electrolyte refill. Plastic or steelarmoring is available for the DO electrode to protect it from harsh fieldconditions. The DO electrodes can be easily cleaned with warm water formany applications and come with a vial of cleaning solution for the counterelectrode.
The CellOx 325 DO electrode is ideal for monitoring DO levels in lakes, rivers,streams, in control measurements, in laboratories, and biotechnologyapplications. With the Oxi 3205 handheld field meters the DO electrodesare ideal for routine field measurements. The Oxi 3210 meter raises theperformance level of the DO electrodes to a point where they are recommended forhighly precise control, quality assurance, and field measurements. Withthe Oxi 1970i rugged field meters the DO electrode measurements can becontrolled with a computer, stored in the 800 dataset memory, and supportedusing GLP requirements.
What is Dissolved Oxygen (DO)?
Some oxygen is dissolved in practically every liquid. For example, at atemperature of 68 øF (20 øC) and an atmospheric pressure of 1013 mbarsaturated water contains about 9 mg/l DO. Ethanol can contain up to 40mg/l whereas glycerol only has about 2 mg/l.
Each liquid takes up oxygen until the partial pressure of oxygen in theliquid is in equilibrium with the air or gas phase in contact with it. Theactual oxygen concentration depends on a number of factors, such as temperature,air pressure, oxygen consumption by microorganisms in a biodegradation processor oxygen production by algae, etc.
The DO concentration is important for the:
- Living conditions for fish and microorganisms in waters
- Degradation processes in wastewater treatment
- Corrosion processes in pipelines
- Shelf life of beverages, etc.
The determination of the DO concentration was formerly carried out by theWINKLER titration method. Today electrochemical measurement is arecognized method in numerous standard procedures.
In its simplest form a DO electrode contains a working electrode and acounterelectrode. Both dissolved oxygen electrodes are located in anelectrolyte system which is separated from the sample by a gas-permeablemembrane. The working DO electrode reduces the oxygen molecules tohydroxide ions. In this electrochemical reaction a current flows from thecounterelectrode to the working DO electrode. The more DO present in thesample, the larger the current signal generated by the dissolved oxygenelectrode. A meter connected to the DO electrode calculates the oxygenconcentration in the sample from this signal.
Why Measure DO?
Dissolved oxygen (DO) is the amount of oxygen (O2) dissolved inwater. DO measurements provide one of the best indicators of the health ofa water ecosystem, as oxygen is a necessary element for all forms of life,including aquatic life. Oxygen enters water at the water surface throughdirect exchanges with the atmosphere. It is also produced as a byproductof plant and phytoplankton photosynthesis. A decrease in DO levels istypically associated with an organic pollutant. DO is used by plants andanimals for respiration, and by aerobic bacteria in the process ofdecomposition. When organic matter (such as animal waste or improperlytreated wastewater) enters a body of water, algae growth increases. As theplant material dies off and decomposes, DO levels decrease. If the waterat the surface is not mixed with deeper water layers, the water?s DO levelscan become stratified. DO levels can also vary according to the time ofday, weather, and temperature. DO in water can range from 0-18 parts permillion (ppm), but most natural water systems require 5-6 ppm to support adiverse population. As DO levels drop below 5.0 mg/L, aquatic life is putunder stress. As DO levels decrease, pollution-intolerant organisms arereplaced by pollution-tolerant worms and fly larvae. If DO levels fallbelow 1-2 mg/L for a few hours, large fish kills can result.
Measuring Principle: Membrane covered galvanic sensor
Temperature Compensation: IMT
Measurement Range at 68øF (20øC): 0 to 50 mg/L O2, 0 to 600%O2 saturation, 0 to 1250 mbar O2 partial pressure
Temperature Range: 32 to +122øF (0 to +50øC)
Maximum Allowed Overpressure: 87 psi (6 bar)
Immersion Depth: 2.36 inches min/65.6 ft max (depending on cable length)(6 cm min/20 m max(depending on cable length))
Operating Position: Any
0.1 ft/s (3 cm/s) at 10% meas. accuracy
0.33 ft/s (10 cm/s) at 5% meas. accuracy
0.59 ft/s (18 cm/s) at 1% meas. accuracy
Zero Signal: <0.1% of the saturation value
Response Time at 68øF (20øC):
t90 (90 % of indication of end valueafter) < 10 s
t95 (95 % of indication of end valueafter) < 16 s
t99 (99 % of indication of end valueafter) < 60 s
Self Consumption at 68øF (20øC): 0.008 ug h-1 (mg/L)-1
Drift: Approximately 3%/month in operation conditions
Working Life: Approximately 6 months per electrolyte refill
Cable Length: Varies
Cable Plug: 8 pin socket
Cable Diameter: 0.24 inches (6 mm)
Membrane Head: POM
Thermistor Housing: VA-steel 1.4571
Cable Screw Joint: POM
Size of Probe:
Electrode Shaft: 5.7 inches L x 0.6 inchesDia. (145 mm L x 15.25 mm Dia.)
Membrane thickness: 0.51 mil (13 um)
Weight: 0.37 lb. (170 g) w/4.9 ft (1.5 m) of cable