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The SE 558 Memosens pH Sensor is specifically engineered for high-purity water applications, particularly where conductivity exceeds 10 μS/cm. Designed for low-maintenance operation, it offers a reliable alternative to traditional, high-maintenance liquid-filled pH sensors.

SE 558 - pH Sensor for Low Conductivity Liquids

Constructed with Alpha pH glass, three ceramic junctions, and a KCl reservoir, the SE 558 ensures stable and accurate measurements. An integrated NTC 30K temperature sensor provides precise temperature compensation for process media, enhancing measurement accuracy.

The integration of Memosens digital technology—combined with reduced maintenance demands—significantly lowers the total cost of ownership. The SE 558 is fully compatible with all Knick M4 transmitters, making it a flexible and efficient choice for demanding applications.

The SE 558 is suitable for use with any M4 Knick transmitter.

QUICK SPECS

Range: 0 … 14 pH
Temperature:  32 … 212°F (0 … 100°C)
Pressure:  Full vacuum … 43 psig (-1 … 3 bar)
Sensor Material: Alpha pH
Diaphragm/Junction: 3X Ceramic
Electrolyte: Gel
Reference Electrode: Ag/Ag Cl – Silamid®

TYPICAL APPLICATIONS

  • Boiler Condensate
  • Boiler Blow-down
  • Reverse Osmosis (RO) Systems
  • Water for Injection (WFI)
  • Ultra-pure water

SE 558 pH Sensor Anatomy

1 – SENSOR HEAD: Memosens Digital Sensing Technology

Memosens sensors offer significant advantages in terms of usability and operational cost savings:

  • Inductive, submersible connection: Eliminates measurement interference caused by moisture and humidity, which are common in many process environments.
  • Galvanic isolation: Prevents measurement errors from electrical noise or ground loops—particularly advantageous when using plastic sensor holders.
  • Off-site calibration and diagnostics: Sensors can be calibrated and tested in a controlled shop or laboratory setting, minimizing time spent on field maintenance and reducing overall process downtime.

SE 558 Anatomy

2 – ELECTROLYTE:

  • Gel Electrolyte: The use of a gel electrolyte eliminates the need for refilling, making the sensor a low-maintenance and user-friendly solution.
  • KCl Rings: Incorporating a solid KCl reservoir, the sensor features KCl rings that help prevent electrolyte depletion from the reference system, thereby enhancing sensor longevity.

3 – REFERENCE ELECTRODE: Ag/Ag Cl – Silamid®

The Silamid reference electrode features a glass tube internally coated with silver and filled with silver chloride powder. A polyester fiber plug serves as an added barrier to protect against contamination, thereby enhancing sensor longevity.

4 – DIAPHRAGM/JUNCTION: 3X Ceramic

Designed for durability and corrosion resistance, the sensor features a dense ceramic junction that enables the reference system to be pressurized. This pressurization significantly reduces fouling and poisoning, extending calibration intervals and minimizing sensor replacement.

Additionally, the use of three ceramic junctions eliminates flow-related measurement interference and ensures a stable, reliable connection between the reference electrode and the process medium.

5 – SENSOR MATERIAL: Alpha pH glass

Alpha glass is a medium-impedance, fluoride-resistant, and hydrogen-sensitive formulation engineered for demanding applications. It delivers rapid response times, even in low-temperature conditions and ultra-low ionic strength environments with conductivities above 10 μS/cm.