What is Dissolved Oxygen (DO).

Dissolved oxygen is a measure of the quantity of free oxygen molecules in water. The concentration of DO is an important indicator of the health of an aquatic ecosystem because oxygen is essential for almost all forms of life.

Aquaread Dissolved Oxygen Sensor

Aquaread developed our own optical dissolved oxygen sensor back in 2010. It can be found on almost all of our Aquaprobes and on every Aquasonde. Its special design maximises the sensor cap life meaning longer that 3 years use between cap changes.

Dissolved Oxygen

Key Features

  • Replaceable aluminium caps feature the Luminophore membrane
  • DO Measurement range: 0-500% / 0-50mg/L
  • Simple 2-point calibration
  • Internal temperature, salinity and air pressure compensation
  • Easy maintenance
  • Holds calibration for 6 months
  • No flow of water is required to achieve stable readings

Our DO sensors come as standard on many of our probes, below are some examples. To see all of the probes that feature DO please visit the water quality section.

AP-700 & AP-800

AP-700 & AP-800

Basic Water Monitoring Packages



Advanced portable multi-parameter Aquaprobe.



The Aquasonde-2000 has 2 spare ports. They can house either 1x ISE sensor and 1x Optical sensor. Or it can house 2x ISE sensor.

Tech behind the optical probe

The Aquaread optical dissolved oxygen probe works on the principle of Dynamic Luminescence Quenching. A gas-permeable material known as a luminophore is excited with short bursts of blue light, which causes molecules in the luminophore to emit red photons.

By measuring the delay of the returned red photons with respect to the blue excitation, the level of dissolved oxygen present can be determined. The optical method has various advantages over the historical galvanic method for measuring dissolved oxygen.

Simple calibration

The DO sensor is easy to calibrate. There are only 2 points to calibrate, first the 100% point which you can calibrate in the air. The second is performed in zero oxygen solution. The Aquameter will do the rest, checking it’s in the correct solution and checking for stability prior to completing the calibration.

Auto salinity compensation

When measuring % saturation the salinity of the water has an influence on the dissolved oxygen % saturation measurement. The DO sensor has a built-in conductivity sensor meaning that the salinity is calculated, this value is then used for auto compensation giving the most accurate measurements with no extra user input.

More cost-effective alternative to optical?

Aquaread also offer an alternative DO sensor found on the entry level AP-700 and AP-800 Aquaprobes. These probes use the galvanic method for DO measurement. With this sensor oxygen is consumed from the sample as it’s crossed the sensors membrane. Once inside the sensor it reacts with the electrolyte solution inside the membrane cap causing a current, which is measured.

Dissolved Oxygen

Whilst both sensors have the same great sensor resolution and accuracy, the galvanic sensors do require more maintenance by means of regular cap and electrolyte solution replacement. Also, as oxygen is consumed across the membrane these sensors are not ideal for use in still waters. Caps must be replaced every month followed by a fresh calibration.