Galvanic oxygen electrodes for DO meters



  • Temperature compensation
  • Long working life – up to 6 months
  • Protective hood standard

Dissolved Oxygen Electrodes Product Description

The DurOx 325 dissolved oxygen electrodes are easy to use and maintain electrodes for taking dissolved oxygen measurements in the field. The dissolved oxygen electrodes are temperature compensated and waterproof to the IP 68 standard or up to 2 bar. The dissolved oxygen electrodes have a long working life of up to six months from one electrolyte refill. An easy to use calibration vessel is included with each dissolved oxygen electrode as well as a protective hood for field use. The dissolved oxygen electrodes can be easily cleaned with warm water for many applications.

What is Dissolved Oxygen?
Some oxygen is dissolved in practically every liquid.  For example, at a temperature of 68 °F (20 °C) and an atmospheric pressure of 1013 mbar saturated water contains about 9 mg/l oxygen.  Ethanol can contain up to 40 mg/l whereas glycerol only has about 2 mg/l.

Each liquid takes up oxygen until the partial pressure of oxygen in the liquid is in equilibrium with the air or gas phase in contact with it. The actual oxygen concentration depends on a number of factors, such as temperature, air pressure, oxygen consumption by microorganisms in a biodegradation process or oxygen production by algae, etc.

The oxygen 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 dissolved oxygen concentration was formerly carried out by the WINKLER titration method. Today electrochemical measurement is a recognized method in numerous standard procedures.

In its simplest form a dissolved oxygen electrode contains a working electrode and a counterelectrode. Both dissolved oxygen electrodes are located in an electrolyte system which is separated from the sample by a gas-permeable membrane. The working dissolved oxygen electrode reduces the oxygen molecules to hydroxide ions. In this electrochemical reaction a current flows from the counterelectrode to the working dissolved oxygen electrode. The more dissolved oxygen present in the sample, the larger the current signal generated by the dissolved oxygen electrode. A meter connected to the dissolved oxygen electrode calculates the oxygen concentration in the sample from this signal.

Why Measure DO?
Dissolved oxygen (DO) is the amount of oxygen (O2) dissolved in water.  Dissolved oxygen measurements provide one of the best indicators of the health of a water ecosystem, as oxygen is a necessary element for all forms of life, including aquatic life.  Oxygen enters water at the water surface through direct exchanges with the atmosphere.  It is also produced as a byproduct of plant and phytoplankton photosynthesis.  A decrease in dissolved oxygen levels is typically associated with an organic pollutant.  Dissolved oxygen is used by plants and animals for respiration, and by aerobic bacteria in the process of decomposition.  When organic matter (such as animal waste or improperly treated wastewater) enters a body of water, algae growth increases.  As the plant material dies off and decomposes, dissolved oxygen levels decrease.  If the water at the surface is not mixed with deeper water layers, the water’s dissolved oxygen levels can become stratified.  Dissolved oxygen levels can also vary according to the time of day, weather, and temperature.  Dissolved oxygen in water can range from 0-18 parts per million (ppm), but most natural water systems require 5-6 ppm to support a diverse population.  As dissolved oxygen levels drop below 5.0 mg/L, aquatic life is put under stress.  As dissolved oxygen levels decrease, pollution-intolerant organisms are replaced by pollution-tolerant worms and fly larvae.  If dissolved oxygen levels fall below 1-2 mg/L for a few hours, large fish kills can result.

Dissolved Oxygen Electrodes Applications

The DurOx 325 dissolved oxygen electrode is ideal for monitoring oxygen levels on fish farms, in control measurements, and at wastewater treatment plants, specifically in the aeration basin. With the Oxi 3205 handheld field meters the dissolved oxygen electrodes are ideal for routine field measurements.  The Oxi 3210 meter raises the performance level of the dissolved oxygen electrodes to a point where they are recommended for highly precise control and quality assurance measurements.

Dissolved Oxygen Electrodes Specifications

Measuring Principle: Membrane covered galvanic sensor
Temperature Compensation: IMT
Measurement Range (68°F (20°C), 1013 hPa): 0 – 50 mg/L O2
Temperature Range: 32 to +104°F (0 to +40°C)
Maximum Pressure: 14.5 psi (105 Pa (1 bar))
Immersion Depth: 1.6 inches min/19.7 ft max (4 cm min/6 m max)
Operating Position: Any
Approach Flow:
      0.08 ft/s (2.5 cm/s) at 10% measeasurement accuracy
      0.16 ft/s (5 cm/s) at 5% measeasurement accuracy
Zero Signal: <1% from saturation value
Response Time at 68°F (20°C):
      t90 (90 % of indication of end value after) < 25 s
      t95 (95 % of indication of end value after) < 40 s
      t99 (99 % of indication of end value after) < 125 s
Self Consumption at 68°F (20°C): 0.006 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
     Membrane Head: POM
     Membrane: FEP
     Thermistor Housing: VA-steel 1.4571
     Shaft: POM
     Cable Screw Joint: POM
Size of Probe:
     Electrode Shaft: 4.3 inches L x 0.7 inches Dia. (110 mm L x 17.5 mm Dia.)
     Membrane thickness: 0.98 mil (25 um)
Weight: 0.5 lb. (220 g) w/9.9 ft (3 m) of cable

Dissolved Oxygen Electrode Options

DurOx 325-3 Dissolved Oxygen Electrode (PN# 201570)
Galvanic dissolved oxygen electrode with OxiCal®-SL calibration and storage vessel, waterproof plug (IP 67), cable length 9.9 ft (3 m), 1 exchange membrane head and electrolyte, cleaning solution, and abrasive foil.


DurOx 325-6 Dissolved Oxygen Electrode (PN# 201571)
Galvanic dissolved oxygen electrode with OxiCal®-SL calibration and storage vessel, waterproof plug (IP 67), cable length 19.8 ft (6 m), 1 exchange membrane head and electrolyte, cleaning solution, and abrasive foil.



SK-D Dissolved Oxygen Electrode Protective Hood (PN# 201575)ontact Us.

ZBK-D Dissolved Oxygen Electrode Accessory Kit (PN# 201578)
Accessory kit with spare parts and maintenance supplies for DurOx® 325 Dissolved Oxygen Electrode.  Includes 3 exchange membrane heads and electrolyte, cleaning solution, and abrasive foil.

OxiCal-D Dissolved Oxygen Electrode Calibration Vessel (PN# 201579)

RL-G Dissolved Oxygen Electrode Cleaning Solution (PN# 205204)
Cleaning solution for DurOx 325 galvanic dissolved oxygen electrodes, 1 bottle with 30 ml.

ELY/G Dissolved Oxygen Electrode Electrolyte (PN# 205217)
Electrolyte for DurOx 325 galvanic dissolved oxygen electrodes, 1 bottle with 50 ml.

WP3-D Dissolved Oxygen Electrode Membrane Heads (PN# 202740)
3 exchange membrane heads for DurOx® 325 dissolved oxygen electrodes


Oxi 3205 Set Handheld Dissolved Oxygen Meter Set
Includes dissolved oxygen meter, DurOx® 325-3 dissolved oxygen probe (9.8ft cable), case & accessories.

CellOx® 325-3 Handheld DO Meter Electrode
Includes 9.8 ft (3m) cable.

DO600 Dissolved Oxygen Meter
Includes DO electrode, protective sensor cap, spare membrane cap, electrolyte, four 1.5V SR44W batteries, and a 48 inch (1.2m) neckstrap.

DO610 Dissolved Oxygen Probe Kit
Includes EC500 Conductivity/TDS/Salinity/pH/Temperature meter, DO600 Dissolved Oxygen probe, and accessories.

DO200ACC Field Dissolved Oxygen Meter Kit
Includes field DO meter, cable with attached DO/temperature probe, and hard sided case.

3B30-010 Oxi 1970i Portable Dissolved Oxygen Meter w/universal power supply

WQ401 Dissolved Oxygen Sensor

WQ-FDO Optical Dissolved Oxygen Transmitter
Includes 25 ft of cable.

WQMS Water Quality Monitoring System
The standard unit includes a datalogger, temperature sensor, pH sensor, conductivity sensor (with a 0-5000µS range unless otherwise specified), and DO sensor.

GL500 Dissolved Oxygen Recorder
Dissolved oxygen recorder for sensor datalogging.  Includes Global Logger Software.  With weather proof enclosure and 12V battery.


PC320 Dissolved Oxygen Controller

EZ100 Dissolved Oxygen Transmitter Display
LCD readout display for both portable use and permanent installations.