Reliable Optical Dissolved Oxygen Measurement
The Oxymax COS61D uses an optical measurement principle based on fluorescence quenching. Oxygen-sensitive molecules are integrated into a fluorescence layer, and the sensor determines oxygen concentration from the duration and intensity of the fluorescence response. This allows the COS61D to measure dissolved oxygen without the polarization and electrolyte replacement associated with conventional electrochemical oxygen sensors.
The sensor can also measure in still water, making it suitable for applications where maintaining a defined flow through the sensor is difficult. Endress+Hauser specifically positions the COS61D for aeration tanks, water treatment, river monitoring, and fish farming.
Designed for Low Maintenance
The optical measurement technology helps reduce routine maintenance requirements while providing long-term measurement stability. The fluorescence layer is oxygen-selective, helping minimize interference from other substances in the process medium.
The sensor stores its calibration data internally, while digital communication provides high EMC protection and reliable transmission of measurement information to the connected transmitter.
Memosens Digital Technology
The COS61D communicates using the Memosens protocol and is designed for use with Endress+Hauser Liquiline transmitters and compatible Memosens measurement systems.
Because calibration data is stored in the sensor, the sensor can be calibrated in the laboratory and exchanged at the measuring point when required. This can simplify maintenance and help reduce process downtime.
Key Technical Highlights
- Measuring range: 0–20 mg/L dissolved oxygen
- Alternative ranges: 0–200 %SAT; 0–400 hPa
- Maximum measured error: 0.01 mg/L or ±1% of reading below 12 mg/L
- Maximum measured error: ±2% of reading from 12 to 20 mg/L
- Response time: t90 ≤ 60 s
- Measurement principle: Optical oxygen measurement based on fluorescence quenching
- Process temperature: -5 to +60 °C
- Process pressure: 1 to 10 bar absolute
- Sensor shaft: Stainless steel 1.4571
- Membrane cap: POM
- Diameter: 40 mm
- Shaft length: 186 mm
- Process connection: G1 or NPT 3/4"
- Communication: Memosens
- Protection: IP68
- Temperature sensor: NTC 30K
Typical Applications
Wastewater Treatment
The COS61D can be used for oxygen measurement and control in activated sludge aeration basins, helping operators monitor dissolved oxygen during biological wastewater treatment. It can also be used for monitoring oxygen levels at wastewater treatment plant outlets.
Water Treatment and Water Quality
The sensor is suitable for monitoring dissolved oxygen in drinking water and process water, as well as water-quality monitoring in rivers, lakes, and other natural water environments.
Fish Farming
Dissolved oxygen is an important parameter for maintaining suitable living and growth conditions in aquaculture. The COS61D can continuously monitor oxygen levels and support oxygen control in fish-farming applications.
Frequently Asked Questions
What does the Endress+Hauser COS61D measure?
The COS61D measures dissolved oxygen (DO) in liquids. It can provide oxygen concentration in mg/L, %SAT, or oxygen partial pressure in hPa.
What is the measuring range of the COS61D?
The standard measuring ranges are 0–20 mg/L, 0–200 %SAT, and 0–400 hPa, under the reference conditions specified by Endress+Hauser.
What is the accuracy of the COS61D?
For measurements below 12 mg/L, the maximum measured error is 0.01 mg/L or ±1% of the reading. From 12 to 20 mg/L, the maximum measured error is ±2% of the reading.
Does the COS61D require water flow?
No. The optical measurement principle allows measurement in still water, so a minimum flow rate is not required for measurement.
How does the COS61D measure dissolved oxygen?
The sensor uses fluorescence quenching. Green light pulses are sent to an oxygen-sensitive fluorescence layer, and the sensor analyzes the resulting red fluorescence response. The response changes according to the oxygen concentration in the medium.
What transmitter can be used with COS61D?
The COS61D is designed for Memosens systems and can be connected to compatible Endress+Hauser Liquiline transmitters, including the Liquiline CM44x family.
How long does the COS61D sensor cap last?
Under the reference operating conditions specified by Endress+Hauser, the sensor cap has an operating life of more than two years, provided it is protected from direct sunlight.
Is the COS61D suitable for wastewater treatment?
Yes. It is specifically designed for applications including activated sludge aeration, wastewater outlet monitoring, process water treatment, and general water quality monitoring.
Is COS61D an electrochemical oxygen sensor?
No. The COS61D is an optical dissolved oxygen sensor. It uses fluorescence-based optical measurement rather than a conventional electrochemical measurement principle.
