Dissolved Oxygen Meters

Dissolved oxygen meters are analytical instruments used to measure the amount of oxygen dissolved in a unit volume of water. It is an important indicator of the degree of usefulness of a sample of water for a specific application.  Air consists of 21 percent oxygen and approximately 78 percent nitrogen by volume. Oxygen dissolves poorly, and can only exist in water in low concentrations. Even so, dissolved oxygen (DO) is essential for the respiration of a wide variety of animals and bacteria in the aquatic environment.  The accurate measurement of dissolved oxygen is critical to many other applications including water treatment plants, sewage treatment works, effluent activated sludge process, river monitoring, fish farming, and any other field where water quality is important. Dissolved oxygen is also one of the key measurements in biotechnical processes, and is essential to maintain quality of the finished product. 

Dissolved oxygen meters interface to one of three common types of dissolved oxygen sensing probes: polarographic sensors, galvanic sensors or optical fluorescence sensors.  Polarographic sensor technology uses an external voltage. The difference in potential between the cathode and anode is less than 0.5 volts. This includes Ross and Clark polarographic types.  A galvanic probe uses requires no external voltage. The difference in potential between the cathode and anode is greater than 0.5 volts. Galvanic probes are more stable and more accurate at low dissolved oxygen levels than polarographic probes. Galvanic probes often operate several months without electrolyte or membrane replacement, resulting in lower maintenance cost.  The optical fluorescence sensor does not use up oxygen during measurement, therefore it does not require stirring.  The device is extremely suitable for long-term measuring periods in groundwater. It is not sensitive to contaminants, sulfurous compounds, or aging.  The sensor has a special coating with fluorescent properties. When light is exposed to the coating it causes fluorescence.  After the exposure of light, the coating continues to produce a short afterglow. The level of oxygen present in the water determines the duration of this fluorescence or afterglow.

Important specifications for dissolved oxygen meters include measuring ranges and accuracies.  Handheld or portable configurations allow dissolved oxygen meters to be used with ease in laboratories, where the operator may be testing several different samples.  Laboratory or benchtop and panel configurations allow for fixtured or permanent setups, while in-situ or field mounted dissolved oxygen meters are useful in remote sensing applications.

Typical features of dissolved oxygen meters include battery packs, filters, event triggers, built-in or self-calibration, extreme environment housings and self-tests or diagnostics.

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Part Numbers for Dissolved Oxygen Meters