Dissolved Oxygen Probe
A dissolved oxygen probe or dissolved oxygen sensor is a device used to measure the amount off free O2 molecules or unbound oxygen molecules in a solution, most commonly water (H2O).
The measurement of dissolved oxygen is normally expressed in either percentage saturation terms or in concentration as a proportion of dissolved oxygen in the measured solution - either PPM or more commonly mg/L.
Our dissolved oxygen probes work using one of two scientific principles - either Fluorescent Optical Dissolved Oxygen Sensors or by using the Clark principle - using a Polarographic or Membrane Type Dissolved Oxygen sensors.
Polarographic or Membrane Type Dissolved Oxygen Sensors
Our range of polarographic or membrane type sensors are designed to offer cost effective and accurate dissolved oxygen measurements in weirs, steams and open vessels with a constant flow.
The polarographic sensors utilise an anode and cathode arrangement surround by a potassium chloride derived electrolyte solution. When dissolved oxygen is present, the oxygen molecules are reduced at the cathode causing a change in current proportional to the amount of dissolved oxygen present. By very accurately measuring this change in current we can derive the amount of dissolved oxygen that was present in the measured solution.
The development of a robust and accurate sensor is attributed to Professor Leland Clark who in his 1956 paper proposed that the anode and cathode be combined into a cell and isolated electrically from the measured solution by an oxygen permeable membrane. Thanks to Leland Clark an Polarographic Dissolved Oxygen sensor with a membrane is often referred to as a Clark Sensor.
We use a PTFE oxygen permeable membrane in our dissolved oxygen cells combined with a potassium chloride derived salt bridge solution. As dissolved oxygen measurements are temperature critical we include an integrated temperature measuring device to provide an accurate and cost effective dissolved oxygen Clark sensor.
The electrochemical signal from a Polarographic or Clark membrane sensor is amplified by a compatible Dissolved Oxygen controller - which calculates the precise percentage saturation of dissolved oxygen, or the dissolved oxygen concentration in mg/L or ppm.
Polarographic Dissolved Oxygen Sensor Measurements
Clark type dissolved oxygen sensors (those using the polarographic membrane method) work by reducing the oxygen that permeates the membrane, which therefore consumes the measured oxygen. As such the dissolved oxygen sensors should be installed in an environment where a constant flow is present to ensure that the readings aren't affected by the measuring method.
Polarographic Dissolved Oxygen Sensor Maintenance
A polarographic membrane dissolved oxygen sensor or Clark sensors requires periodic maintenance which includes removal and replacement of the membrane and the replacement of the electrolyte.
Considering the operating environments of the dissolved oxygen sensors, we've made chaining the electrolyte and membrane of the sensor as simple as possible.
Dissolved Oxygen Sensor Range
The DES-1 is a polarographic dissolved oxygen sensor designed for use with the OD7635 or the OD7685 dissovled oxygen controllers.
Supplied complete in a riser tube for dip mounting - the DES-1 provides an electrochemical signal which is amplified in the controller to give a full arrangement of control options and current output.
Designed with environmental monitoring and process control options the DES-1 is available with a number of additional options, including float for use in rivers, steams and lagoons, and auto-clean nozzles to allow for continuous operation.
As polarographic dissolved oxygen sensors require periodic maintenance - we've made changing the PTFE membrane and recharging the electrolyte solution as simple as possible.
The OD8325 is a submersible dissolved oxygen transmitter designed for use in tanks, streams, pits or weirs. The OD8325 includes an autoclean nozzle for use with a suitable auto-clean system.
The OD8325 offers continous dissolved oxygen measurements with a 4-20mA output signal corresponding to either concentration dissolved oxygen with a range of 0 - 20ppm or percentage saturation of dissolved oxygen with a scale of 0 - 200%.
The OD8325 uses fluorescent technology to reduce the amount of time spent on maintenance and calibration and offers very accurate dissolved oxygen readings even when low levels of DO2 are present.
The OD8525 is an inline dissovled oxygen transmitter designed to be mounted in line or in the flow of a process to deliver continuous dissolved oxygen measurements.
The OD8525 offers continous dissolved oxygen measurements with a 4-20mA output signal corresponding to either concentration dissolved oxygen with a range of 0 - 20ppm or percentage saturation of dissolved oxygen with a scale of 0 - 200%.
The OD8525 uses fluorescent technology to reduce the amount of time spent on maintenance and calibration and offers very accurate dissolved oxygen readings even when low levels of DO2 are present.