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Digital oxygen sensor Memosens COS51E

Memosens 2.0 amperometric oxygen sensor for the wastewater industry and utilities

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Digital oxygen sensor Memosens COS51E

Memosens 2.0 amperometric oxygen sensor for the wastewater industry and utilities

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Benefits

  • Wide measuring range: The amperometric measuring principle and cathode design make the sensor suitable for all wastewater applications from industrial to municipal plants.
  • High accuracy: Thanks to its amperometric, three-electrode design, the sensor provides long-term stable measurement with low drift.
  • Increased plant availability: Memosens technology and Liquiline transmitters enable plug & play for fast commissioning and sensor exchange.
  • Non-contact, inductive signal transmission ensures maximum process integrity.
  • Memosens 2.0 digital technology makes the sensor ready for predictive maintenance and IIoT services since it offers extended storage of calibration and process data.

Integrated technologies

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Digital oxygen sensor Memosens COS51E

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Engineered for confidence

Our instruments are designed for long‑lasting performance, precise measurement, and dependable operation in demanding industrial environments. Each product includes a standard manufacturer’s warranty that reflects our commitment to quality and to the trust you place in our solutions.

Should a warranty case occur, the device will be assessed and the applicable remedy will be provided in line with the warranty terms – helping ensure a reliable and efficient resolution and supporting continued operation of your measurement point.

Request for extended warranty

If you require extended warranty coverage, simply contact your local Endress+Hauser representative. Our experts will advise you on the available options to match your application and risk profile, helping you protect your investment, reduce unexpected repair costs, and ensure reliable long‑term operation beyond the manufacturer's warranty period.

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Warranty terms apply

The manufacturer's warranty and extended warranty are subject to specific conditions. For full details, please refer to the locally applicable General Terms and Conditions (GTC), which can be found on the respective country page of our website.

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Endress+Hauser’s qualified service engineers ensure your measurement devices are commissioned right the first time, delivering application‑aligned accuracy, regulatory compliance, and operational confidence from startup onwards, anywhere in the world.

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Make life easier, increase process safety and stay connected with Memosens 2.0 digital technology.

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Product information

Memosens COS51E: digital, amperometric oxygen sensor
Memosens COS51E digital oxygen sensor
Specifications
Measuring / Application task Oxygen
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Description

Memosens COS51E is perfectly suited for all wastewater and utility applications including hazardous areas. The sensor is highly accurate and moisture-resistant ensuring the safety of your processes. COS51E features Memosens 2.0 digital technology. It is able to store more calibration and process data and thus provides the perfect basis for predictive maintenance and IIoT services. Designed to be low-maintenance with a long operating life, the sensor offers outstanding value for money.

Field of application

Memosens COS51E measures the dissolved oxygen concentration in:

  • Wastewater treatment plants: - O2 control in the aeration basin - Process water treatment and monitoring
  • Utilities of all industries: - O2 control in the biological treatment - Process water treatment and monitoring
  • Water works: - Status monitoring of drinking water (oxygen enrichment, corrosion protection, etc.) - Water quality monitoring in rivers, lakes or seas

The sensor is suitable for hazardous area use (ATEX, FM, CSA).

Benefits
  • Wide measuring range: The amperometric measuring principle and cathode design make the sensor suitable for all wastewater applications from industrial to municipal plants.
  • High accuracy: Thanks to its amperometric, three-electrode design, the sensor provides long-term stable measurement with low drift.
  • Increased plant availability: Memosens technology and Liquiline transmitters enable plug & play for fast commissioning and sensor exchange.
  • Non-contact, inductive signal transmission ensures maximum process integrity.
  • Memosens 2.0 digital technology makes the sensor ready for predictive maintenance and IIoT services since it offers extended storage of calibration and process data.
Predecessors
Downloads
Most downloaded
Technical Information (TI)
TI Memosens COS51E Amperometric oxygen sensor for water, wastewater and utilities
English version - 10/2025
Download
Operating Instruction (BA)
BA Memosens COS51E Amperometric oxygen sensor with Memosens 2.0 technology
English version - 10/2025
Download
Short Instruction (KA)
Memosens COS51E Amperometric oxygen sensor with Memosens 2.0 technology
English version - 10/2021
Download
The CAD Drawings will be available after the configuration.
All downloads
101 Downloads
Technical Information (TI)
Most downloaded
TI Memosens COS51E Amperometric oxygen sensor for water, wastewater and utilities
English version - 10/2025
Download
Operating Instruction (BA)
Most downloaded
BA Memosens COS51E Amperometric oxygen sensor with Memosens 2.0 technology
English version - 10/2025
Download
Short Instruction (KA)
Memosens COS51E Amperometric oxygen sensor with Memosens 2.0 technology
English version - 10/2021
Download
Installation Instructions (EA)
EA Kit COS41/COS51D/E for maintenance of the Oxymax W COS41/COS51D and Memosens COS51E oxygen
sensors
English version - 05/2023
Download
Ex Safety Instruction (XA)
Memosens COS22E Memosens COS51E Supplement to BA02145C
Supplement to BA02146C
Safety instructions for electrical apparatus in explosion-hazardous
areas
English version - 11/2021
Download
Ex Safety Instruction (XA)
XA Memosens oxygen sensors NEPSI Ex ia IIC T6/ T4 Ga
Safety instructions for electrical apparatus in explosion-hazardous areas
English version - 02/2026
Download
Ex Safety Instruction (XA)
Memosens COS22E Memosens COS51E EAC Ex 0Ex ia IIC T6 … T4 Ga X
Safety instructions for electrical apparatus in explosion-hazardous
areas
English version - 05/2022
Download
Ex Safety Instruction (XA)
Memosens COS22E Memosens COS51E KOR Ex ia IIC T6… T4 Ga
Safety instructions for electrical apparatus in explosion-hazardous
areas
English version - 03/2022
Download
Ex Safety Instruction (XA)
XA Memosens COS22E Memosens COS51E EAC Ex 0Ex ia IIC T6 … T4 Ga X
Safety instructions for electrical apparatus in explosion-hazardous areas
English version - 07/2025
Download
Ex Safety Instruction (XA)
XA Memosens COS22E Memosens COS51E Supplement to BA02145C
Supplement to BA02146C
Safety instructions for electrical apparatus in explosion-hazardous areas
English version - 01/2025
Download
Ex Safety Instruction (XA)
Memosens COS22E Memosens COS51E UK Ex II 1G Ex ia IIC T6… T4 Ga
Safety instructions for electrical apparatus in explosion-hazardous
areas
English version - 03/2022
Download
Ex Safety Instruction (XA)
Memosens COS22E Memosens COS51E Supplement to BA02145C
Supplement to BA02146C
Safety instructions for electrical apparatus in explosion-hazardous
areas
English version - 11/2021
Download
Ex Safety Instruction (XA)
XA Memosens oxygen sensors IS Class I Div 1 Groups A, B, C, D
Ex ia IIC T6... T4 Ga
Class I Zone 0 AEx ia IIC T6... T4 Ga
Safety instructions for electrical apparatus in explosion-hazardous areas
English version - 05/2026
Download
Ex Safety Instruction (XA)
XA Memosens COS22E Memosens COS51E Supplement to BA02145C
Supplement to BA02146C
Safety instructions for electrical equipment for explosion-hazardous areas
English version - 07/2026
Download
Special Documentation (SD)
SD COV45 Maintenance Kit for COS41,
COS51D and COS51E
English version - 10/2024
Download
Fields of Activities (FA)
Sensors, transmitters, compact devices and assemblies Experts in Liquid Analysis
English version - 02/2026
Download
Fields of Activities (FA)
水質分析の専門知識 センサからすべてを備えた
ターンキーソリューションまで
Japanese version - 06/2025
Download
Fields of Activities (FA)
Kompetenz in der Flüssigkeitsanalyse Vom Sensor bis zur schlüsselfertigen Komplettlösung
German version - 09/2022
Download
Fields of Activities (FA)
Sıvı analizinde uzmanlık Sensörlerden komple anahtar teslim çözümlere
Turkish version - 11/2023
Download
Fields of Activities (FA)
Expertise in liquid analysis From sensors to complete turnkey solutions
English version - 09/2022
Download
Fields of Activities (FA)
Sensoren, Messumformer, Kompaktgeräte and Armaturen Kompetenz in der Flüssigkeitsanalyse
German version - 02/2026
Download
Fields of Activities (FA)
Sensori, trasmettitori, dispositivi compatti e armature Sensori, trasmettitori,
dispositivi compatti e armature
Esperti in materia di analisi dei
liquidi
Italian version - 06/2026
Download
Fields of Activities (FA)
Endress+Hauser 水質分析計ファミリ ラインナップと事例
Japanese version - 03/2017
Download
Electrolytes
COV45-41TNx_51Txx (Canada (French)) Electrolyte for COS41/COS51D/E
French version - 01/2025
Download

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Memosens COS51E: digital, amperometric oxygen sensor
Memosens COS51E digital oxygen sensor

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Spare parts and accessories

further parts
further parts

COV45 maintenance kits COS41/COS51x

further parts
further parts
Order code COV45-
further parts
further parts

Zero-point gel COY8

further parts
further parts
Order code COY8-
further parts
further parts

Kit COSxx Protection cage Standard

further parts
further parts
Order code 71495128
further parts
further parts

Kit COSxx Protection cage 8,5 mm holes

further parts
further parts
Order code 71495126
Spare parts & accessories

Selection of compatible products

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