Reliable Optical Dissolved Oxygen Measurement

The Endress+Hauser COS61D is a digital optical oxygen sensor designed for continuous dissolved oxygen measurement in water, wastewater and utility applications.

Unlike traditional amperometric oxygen sensors, the COS61D uses an optical fluorescence measuring principle, which reduces maintenance requirements and provides stable measurement performance over long operating periods.

The sensor is designed for applications where accurate oxygen monitoring is essential, such as wastewater aeration control, water quality monitoring and aquaculture.

Optical Fluorescence Measuring Principle

The COS61D uses an oxygen-sensitive fluorescence layer to measure dissolved oxygen concentration.

The measurement principle works by:

1. 
   The sensor emits green light pulses to the fluorescence layer.
   
2. 
   Oxygen-sensitive molecules react and produce red fluorescence.
   
3. 
   The intensity and duration of the fluorescence signal are affected by oxygen concentration.
   
4. 
   The sensor calculates dissolved oxygen values based on these changes.
   

Benefits of optical measurement:

• 
  No oxygen consumption during measurement
  
• 
  No electrolyte replacement
  
• 
  Reduced maintenance requirements
  
• 
  Long-term measurement stability
  

Memosens Digital Technology

The COS61D uses Memosens digital technology, enabling secure communication between sensor and transmitter.

Key advantages:

• 
  Calibration data stored inside the sensor
  
• 
  Easy sensor replacement
  
• 
  Laboratory calibration capability
  
• 
  Improved data integrity
  
• 
  Reduced commissioning time
  

The sensor can be connected with Endress+Hauser Liquiline transmitters for complete liquid analysis solutions.

Designed for Water and Wastewater Applications

The COS61D is optimized for applications requiring continuous dissolved oxygen monitoring.

Typical measurement areas include:

• 
  Aeration tanks
  
• 
  Biological wastewater treatment
  
• 
  Process water treatment
  
• 
  Drinking water monitoring
  
• 
  Surface water monitoring
  
• 
  Fish farming
  

Low Maintenance Oxygen Sensor

Compared with conventional electrochemical oxygen sensors, the COS61D reduces routine maintenance because the optical measuring principle does not require electrolyte replacement.

This makes it suitable for installations where:

• 
  Long operating intervals are required
  
• 
  Maintenance access is limited
  
• 
  Stable oxygen control is important
  

Key Features

• 
  Digital optical dissolved oxygen sensor
  
• 
  Fluorescence-based oxygen measurement technology
  
• 
  Memosens digital communication
  
• 
  Low maintenance operation
  
• 
  No electrolyte replacement required
  
• 
  Fast and stable oxygen measurement
  
• 
  Suitable for continuous process monitoring
  
• 
  Compatible with Liquiline transmitters
  
• 
  Calibration data stored in sensor
  
• 
  Stainless steel sensor body design
  
• 
  Suitable for water, wastewater and utility applications

Technical Specifications

• 
  Measuring principle: Optical dissolved oxygen measurement
  
• 
  Measuring range: 0 to 20 mg/l
  
• 
  Saturation range: 0 to 200 %SAT
  
• 
  Partial pressure range: 0 to 400 hPa
  
• 
  Process temperature: -5 to 60 °C
  
• 
  Maximum process pressure: 10 bar abs
  
• 
  Sensor material: Stainless steel 1.4571
  
• 
  Temperature sensor: NTC 30K
  
• 
  Sensor diameter: 40 mm
  
• 
  Connection: Fixed cable or TOP68 plug-in head

Typical Applications

Wastewater Treatment

The COS61D is widely used for dissolved oxygen monitoring in wastewater treatment plants.

Applications include:

• 
  Aeration basin oxygen control
  
• 
  Activated sludge processes
  
• 
  Biological treatment optimization
  

Accurate oxygen measurement helps maintain stable biological treatment conditions.

Water Treatment

Used for monitoring oxygen levels in:

• 
  Drinking water systems
  
• 
  Process water systems
  
• 
  Water quality monitoring
  

Aquaculture

Dissolved oxygen is a critical parameter in fish farming.

The COS61D helps maintain suitable oxygen levels for:

• 
  Fish growth
  
• 
  Water quality control
  
• 
  Production stability
  

Industrial Utilities

Suitable for industrial applications requiring continuous oxygen monitoring, including:

• 
  Utility water systems
  
• 
  Biological treatment processes
  
• 
  Process water management
  

FAQ

What is Endress+Hauser COS61D?

The COS61D is a digital optical dissolved oxygen sensor designed for measuring oxygen concentration in water and wastewater applications.

What is the difference between COS61D and COS51E?

The COS61D uses an optical fluorescence measuring principle, while COS51E uses an amperometric measuring principle.

COS61D advantages:

• 
  Lower maintenance
  
• 
  No electrolyte replacement
  
• 
  Long-term stable fluorescence measurement
  

COS51E advantages:

• 
  Traditional electrochemical measurement principle
  
• 
  Suitable for applications requiring amperometric technology
  

Does COS61D require electrolyte replacement?

No. The optical measuring principle eliminates the need for electrolyte replacement.

What does COS61D measure?

COS61D measures dissolved oxygen concentration in liquids.

Which transmitters are compatible with COS61D?

COS61D can be connected with Endress+Hauser Liquiline transmitters using Memosens communication.