Dissolved oxygen (DO) sensors and probes detect levels of dissolved oxygen in liquids, typically water, usually for biological measurements and for industrial process applications. Readouts will usually display dissolved oxygen concentration in either parts per million or milligrams per liter.

Another type of readout involves comparing a calculation of the maximum dissolved oxygen concentration with the actual concentration, expressed as a percentage. The variables that affect the maximum concentration are the atmospheric pressure just above the liquid, the temperature of the liquid, and the presence of other substances in the liquid.

Here are a few different types of dissolved oxygen sensors:

1. Galvanic dissolved oxygen sensors employ electrodes and remain stable and accurate even at low dissolved oxygen concentrations. Another benefit is that they do not require frequent replacement of electrolyte fluid.

2. Polarographic dissolved oxygen sensors also employ electrodes, but require the addition of an external voltage input and relatively frequent replacement of electrolyte fluid.

3. A optical dissolved oxygen sensor does not use electrolyte fluid at all, but an optode instead. In this case, an optical cable detects a film that reacts to dissolved oxygen with fluorescence.

Action Steps
The best contacts and resources to help you get it done

Shop dissolved oxygen sensor suppliers that also carry accessories

Various types of dissolved oxygen sensor instruments require different supplies to keep them operating. Especially if you intend to put your dissolved oxygen sensor equipment to heavy use, shop DO sensor sources that also carry the supplies.

I recommend: Veriner carries a sensor with a range of 0 to 14 mg/l. They also sell filling solution, calibration solution, membranes and other supplies to keep the sensor operating. Sensorex sells both lab and process dissolved oxygen probes. They also carry supplies and accessories to help their customers get longterm use out of their products.

Locate industrial dissolved oxygen sensors that suit your needs

Controlling dissolved oxygen levels in industrial processes helps optimize efficiency of production and quality of product. Chemical reactions often require the control of oxygen levels. Some dissolved oxygen sensor manufacturers specialize in this type of equipment.

I recommend: Mettler Toledo carries several products for sterile processes, as well as low level situations. They also have a waste water dissolved oxygen sensor. If you're looking for hand-held dissolved oxygen meters, then Instrumart is your place. They carry several models designed specifically for industrial processes.

Buy a quality optical dissolved oxygen sensor

Sometimes divers and biologists prefer the newer optical technology which requires relatively less care. Some conventional sensors have more variables due to changes in the electrolyte fluid during heavy use. Also, optical sensors often work better in stagnant water.

I recommend: AADI specializes in oceanic science and has many quality sensors, including the optical dissolved oxygen sensor. Another source is Global Water Instrumentation, Inc. which carries a model that features long life, bio-fouling resistance; their unit is unaffected by water current or a lack thereof.

Tips & Tactics

Helpful advice for making the most of this Guide

• •  If you have a fish farm, get a dissolved oxygen sensor to help optimize the respiration and growth of your fish.