What is a Dissolved Oxygen Meter

Antoine Lavoisier coined the term ‘Oxygen’ in 1777. He coined the word using the Greek words ‘oxys’ meaning acid and ‘genes’ meaning ‘producer’ as he thought that oxygen was a part of all acids. While, today we know that this is not true, what we do know is that all living organisms need oxygen to survive.

Oxygen is the third most common abundant chemical by mass in the universe, the first two being hydrogen and helium. It is produced in the earth’s atmosphere by plants during photosynthesis. The atomic weight of oxygen is 8 and the valence is -2. The most common oxygen compound is the water. It also forms an integral part of silica.

What is Dissolved Oxygen

While some gases like Nitrogen and Ammonia chemically react with water, other gases like Oxygen do not react with water at all. Dissolved Oxygen can be defined as physical distribution of oxygen in water. The main sources of dissolved oxygen in water are the atmosphere and photosynthesis. Waves and flowing water mix the air and water while aquatic plants produce oxygen as a by-product during photosynthesis.

The amount of dissolved oxygen that can be present mainly depends on the water temperature, salinity and atmospheric pressure. Additionally, the amount of dissolved oxygen can increase with a decrease in temperature of the water and can increase with an increase in atmospheric pressure.

What is a Dissolved Oxygen Meter

A dissolved oxygen meter is used to measure the amount of oxygen present in a unit volume of water. Now the next question that arises is, why do I need to measure the quantity of oxygen in water? This is because it indicates if the water is useful for a specific application like water treatment plants, sewage treatment works, river monitoring and
fish farming.

The various types of oxygen meter available are:

• Polarographic (Clark Cell Method) Sensor Oxygen Meter: use an external voltage keeping the potential difference between the anode and cathode to less than 0.5 volts.
• Galvanic Sensor Oxygen Meter: does not use an external voltage and the difference between the anode and cathode is greater than 0.5 volts. These are more stable and accurate when compared to the Polarographic oxygen meters
• Optical Fluorescence Oxygen Meter: are extremely suitable for long-term measurements in groundwater as it is not sensitive to contaminants or for that matter, aging.

Ranges and accuracies offered are the key specifications to look at while purchasing an oxygen meter. Portable handheld equipments are very handy at location points. Permanent setups are useful in laboratories.

The typical features that should be available with the Oxygen Meter that you are purchasing are:

• Self Calibration
• Event Triggers
• Battery Packs
• Filters

The technical data that a portable oxygen meter should be able to capture is:

• Oxygen range: 0.01 mg/l – 2000 mg/l
• Resolution: 0.01 mg/l
• Temperature range: 0 – 50 C
• Automatic air pressure compensation
• Automatic temperature compensation
• Correction for salinity

Dissolved Oxygen Transmitter

The dissolved oxygen transmitter is based on the principle of an oxygen sensor attached to an acoustic transmitter. When the equipment is turned on, it determines the level of dissolved oxygen is water and transmits it to a hydrophone connected to the receiver. Multiple transmitters that receive signals at different frequencies can be used to receive multiple data. The distance over which the signal can travel depends on various factors including the occurrences of waves, bubbles and ship traffic. The dissolved oxygen meter uses the galvanic type of oxygen sensor to measure the level of oxygen in the water.
The dissolved oxygen transmitters are attached to aquatic animals. When externally attached to them, these transmitters provide information has to how variation in the oxygen level measurements impacts the behavior of the individuals temporally and spatially.

Uses Of Dissolved Oxygen Meter

Some of the industrial uses of a dissolved oxygen meter are:

• Analysis of boiler feed water for industries
• Waste water treatment plants
• Pollution control in rivers and lakes
• Ionic concentration measurement for pharmaceutical companies
• Analysis of drinking water

This list will grow with time. There was a time when philosophers were poisoned because they thought freely and unconventionally and today scientific expansions know no limit. The main point is that advancement never stops and as long as we exist we will keep on moving towards the newer and better tomorrow. We need to contribute our bit towards this development in any fashion that we can…it is not the question of quantity, but we must and I am sure we will.