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Digital oxygen sensor
Oxymax COS61D

Digital oxygen sensor
Oxymax COS61D ©Endress+Hauser
Digital oxygen sensor
Oxymax COS61D ©Endress+Hauser
Digital oxygen sensor
Oxymax COS61D ©Endress+Hauser

The concentration of oxygen dissolved in a liquid can be measured using the amperometric or optical measuring principles. This video shows what it is about and how these measuring principles work.

Memosens optical oxygen sensor for water, wastewater and utilities

Oxymax COS61D is a high-performance, digital oxygen sensor that offers fast, accurate and drift-free measurement. It supports your process with low maintenance, high availability and easy handling. The sensor's long-term stable fluorescence layer is exclusively oxygen-selective (interference-free), ensuring consistently reliable measurement. Thanks to Memosens digital technology, the Oxymax COS61D combines maximum process and data integrity, and facilitates simple lab calibration.

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  • Benefits

    • Minimum maintenance, maximum availability

    • Fast, drift-free measurement for precise aeration control and process monitoring

    • Long-term stability for increased process safety

    • Outstanding performance in all aeration processes (SBR, Anamox, etc.)

    • Chemical-free...

  • Field of application

    Oxymax COS61D measures the dissolved oxygen concentration in:

    • Wastewater treatment plants:
      - O2 control in the aeration basin
      - Process water treatment and monitoring

    • Water works:
      - Status monitoring of drinking water (oxygen enrichment, corrosion...

Features and specifications



  • Measuring principle

    Sensor Oxygen

  • Application

    Aeration tank, river monitoring, water treatment, fish farming

  • Characteristic

    Digital, optical measurement of dissolved oxygen based on fluorescence quenching
    Measurement possible in still water

  • Measurement range

    0 to 20 mg/l
    0 to 200 %SAT
    0 to 400 hPa

  • Measuring principle

    Oxygen-sensitive molecules (marker) are integrated in an optical active layer (fluorescence layer). The fluorescence layer surface is in contact with the medium. The sensor optics are directed at the back of the fluorescence layer. The sensor optics transmit green light pulses to the fluorescence layer. The markers respond (fluoresce) with red light pulses. The duration and intensity of the response signals depend directly on the oxygen contents or partial pressure.

  • Design

    Calibration data saved in sensor
    High degree of EMC protection

  • Material

    Sensor shaft: stainless steel 1.4435
    Membrane cap: POM

  • Dimension

    Diameter: 40 mm (1.57 inch)
    Shaft length: 186 mm (7.32 inch)

  • Process temperature

    -5 to 60 °C
    (20 to 140 °F)

  • Process pressure

    Max. 10 bar abs
    (Max. 145 psi)

  • Temperature sensor

    NTC 30K

  • Connection

    Process connection: G1, NPT 3/4"
    Cable connection: fixed cable or TOP68 plug-in-head

Documents / Manuals / Software

Accessories / Spare parts

Order code
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    • Order code 50081787

      COY 3-SK membrane protective basket

      for immersion of diss. oxygen sensors COS31/41/51D/61/61D in fish ponds.

    • Order code 51518599

      Calibration cap, COS31/41/61/51D/61D//71

    • Order code 71110801

      Cleaning head COS61/61D, 6 or 8mm

    • Order code 71110802

      Cleaning head COS61/61D 1/4"

    • Order code 71072583

      Cleaning unit, 230 V

    • Order code 71096199

      ISEmax Compressor cleaning unit 110V

      with rail mount

    • Order code 51500832

      Junction box RM

      to lengthen the cable for Memosens/CUS31/41. Protection class IP 65, with 2x PG 13.5

    • Order code COY8-

      Zero-point gel COY8

      Zero point: Verification, calibration, adjustment at zero point of oxygen and disinfection sensors ::Amperometric and optical sensors ::12, 25 and 40mm diameter ::Application in the lab, in the field