COS51E

Summary

Product identification

• Product Name: Memosens COS51E
• Type: Amperometric oxygen sensor for water, wastewater and utilities
• Technology: Memosens 2.0
• Document: TI01620C/07/EN/02.22-00

Application

Typical applications include:

• Wastewater treatment plants:
  • Oxygen control in activated sludge basins
  • Treatment and monitoring of process water
• Water works:
  • Status monitoring of drinking water
  • Monitoring of water quality in rivers, lakes or oceans
• Industrial utilities:
  • Oxygen control in biological treatment phase
  • Treatment and monitoring of process water

The sensor has ATEX, IECEx, CSA C/US, NEPSI, JapanEx and INMETRO approval for use in hazardous areas Zone 0, Zone 1 and Zone 2. It also has CSA C/US approval for hazardous areas Class I Division 1 in explosive gas atmospheres and is suitable for Class I Division 2.

Measuring principle

Amperometric oxygen measurement involves oxygen diffusion through a membrane, reduction to hydroxide ions (OH⁻) at the working electrode, and oxidation of silver to silver ions (Ag⁺) at the counter-electrode. The resulting current flow is proportional to the oxygen content. This current is converted by a transmitter and displayed in various units such as mg/l, µg/l, ppm, ppb, Vol%, ppmVol, nA, % SAT, or hPa.

A potentiostatic three-electrode system with a high-impedance reference electrode ensures high signal accuracy and extended calibration intervals by maintaining a constant potential at the working electrode.

Measuring system

A complete measuring system comprises:

• Memosens COS51E oxygen sensor
• A transmitter (e.g., Liquiline CM44x, Liquiline CM42, Liquiline Mobile CML18)
• Measuring cable (e.g., CYK10)
• Optional accessories: assembly (e.g., immersion assembly CYA112, retractable assembly COA451), assembly holder (CYH112), cleaning unit, protection guards.

Dependability and Maintainability

Memosens technology digitizes measured values within the sensor, ensuring reliable detection of sensor failure or connection interruptions. Calibration data and sensor history are stored in the sensor, allowing for independent calibration in a lab environment, quick sensor replacement, and predictive maintenance. The inductive, non-contact data transmission eliminates issues caused by moisture, preventing corrosion and signal distortion.

Input

Measured variables

• Dissolved oxygen [mg/l, µg/l, ppm, ppb, %SAT, %Vol, ppmVol]
• Temperature [°C, °F]

Measuring ranges

• 0 to 100 mg/l
• 0 to 2000 hPa
• 0.00 to 1000 % SAT

Performance characteristics

Response time (t<0xE2><0x82><0x90>)

• COS51E-****TN (black membrane cap): t<0xE2><0x82><0x90> = 3 minutes, t<0xE2><0x82><0x98> = 8 minutes
• COS51E-****TF (white membrane cap): t<0xE2><0x82><0x90> = 30 seconds, t<0xE2><0x82><0x98> = 90 seconds

Signal current in air (at 20 °C / 68 °F)

• **COS51E-**TN: approx. 300 nA
• **COS51E-**TF: approx. 1100 nA

Zero current

• < 0.1 % of the signal current in air

Maximum measured error

• **COS51E-**TN: ≤ ±1 % of the measured value
• **COS51E-**TF: ≤ ±1 % of the measured value

Limit of detection (LOD)

• **COS51E-**TN: 10 ppb
• **COS51E-**TF: 5 ppb

Limit of quantification (LOQ)

• **COS51E-**TN: 20 ppb
• **COS51E-**TF: 10 ppb

Repeatability

• **COS51E-**TN: 20 ppb
• **COS51E-**TF: 100 ppb

Long-term drift

• Zero-point drift: < 0.1 % per week
• Measuring range drift: < 0.1 % per week

Polarization time

• < 60 minutes

Intrinsic oxygen consumption

• **COS51E-**TN: approx. 90 ng/h in air at 25 °C (77 °F)
• **COS51E-**TF: approx. 270 ng/h in air at 25 °C (77 °F)

Process

Process temperature range

• -5 °C to 60 °C (T6)
• 41 °F to 140 °F (T6)

Process pressure range

• 5 bar (72.5 psi) abs.

Environment

Ambient temperature range

• -5 °C to 60 °C (T6)
• 23 °F to 140 °F (T6)

Storage temperature range

• Filled with electrolyte: -5 °C to 60 °C (20 to 140 °F)
• Without electrolyte: -20 °C to 60 °C (0 to 140 °F)

Degree of protection

• IP 68 (10 m (33 ft) water column, 25 °C (77 °F), 30 days)

Mechanical construction

• Dimensions: See diagram (Page 11)
• Weight: 0.3 kg (0.7 lbs)
• Materials:
  • Sensor shaft: POM
  • Membrane cap: POM
  • Working electrode: Gold
  • Counter-electrode and reference electrode: Silver/Silver halide
  • Membrane: ETFE (COS51-****TN), FEP (COS51-****TF)
  • Process connection: Pg 13.5 (Torque max. 3 Nm)
• Membrane thickness: Approx. 50 μm (COS51D-**0), Approx. 25 μm (COS51D-**1)
• Temperature sensor: NTC 30KΩ

Mounting

Installation must ensure uniform flow conditions and prevent air pockets or foam. Avoid buildup on the sensor membrane. Various assemblies are available for different mounting scenarios, including retractable assemblies, immersion assemblies, and flow assemblies. A minimum flow rate of 100 ml/h is required for flow assemblies.

Scope of delivery

The scope of delivery includes the ordered sensor with a protective cap, an accessories set (replacement membrane caps, electrolyte, O-rings, polishing foils), safety instructions (for Ex versions), and a brief operating instruction. Optional accessories like a cleaning unit or replacement caps may be included depending on the configuration.

Accessories

Key accessories include:

• Assemblies: Flowfit CYA251, Flowfit COA250, Cleanfit COA451
• Holders: Flexdip CYH112
• Immersion assemblies: Flexdip CYA112
• Membrane protection guard: Order No. 50081787
• Measuring cables: Memosens data cable CYK10, Memosens laboratory cable CYK20, Memosens data cable CYK11
• Transmitters: Liquiline CM44, Liquiline CM42, Liquiline Mobile CML18, Liquiline Compact CM82, Liquiline Compact CM72
• Converters: Memosens analog converter CYM17
• Software: Memobase Plus CYZ71D
• Maintenance kits: COV45

Disclaimer

This extraction may miss figures, footnotes, or revisions. Contractual data must match the OEM PDF revision used on the project.

Official datasheet (PDF)

Lenntech datasheet mirror