Monitoring the Cooling Tower with pH, ORP, and Conductivity Sensors

Cooling Tower

Cooling towers play a crucial role in industrial processes, efficiently transferring process heat through the use of water as a cooling medium. However, the presence of mineral corrosion, scaling, and biofilm can reduce efficiency and lead to component wear. To maintain the cooling tower’s optimal performance, it is essential to implement reliable monitoring and control measures. In this blog, we will explore the application of pH, ORP, and conductivity sensors in cooling tower monitoring, highlighting the benefits of employing advanced technologies like Memosens.

pH Monitoring for Corrosion Prevention

To prevent mineral deposits on system components, cooling tower water is often treated with acid, such as sulfuric acid, to adjust its pH levels. The acid neutralizes or dissolves alkaline calcium carbonate in the cooling water, preventing lime deposits that may negatively affect heat exchange and cooling system efficiency. Monitoring pH levels using advanced sensors like the German-engineered Knick Memosens pH sensor SE 555 allows for precise pH adjustment, minimizing the impact of corrosion and early detection of process flaws.

ORP Sensors for Water Disinfection

The addition of oxidants in the cooling tower provides disinfection to ensure water and pipeline surfaces are sanitized. During this process, an ORP (Oxidation-Reduction Potential) sensor measures the redox potential to monitor the concentration of oxidants, such as sodium hypochlorite. The required amount of oxidant for complete disinfection can be determined based on this measurement. The German-designed Knick ORP sensor SE-565-ORP, known for its high accuracy and measurement repeatability, is ideal for hygienic processes and sterile applications, making it a suitable choice for cooling tower disinfection.

ORP Sensor SE-565-ORP Overview

The SE-565-ORP sensor is a low-maintenance and pressure-resistant sensor designed for industrial processes. It features a polymer reference system that comes into contact with the process medium through a ceramic junction. The sensor is made of platinum and is intended for simultaneous measurements of ORP (Oxidation-Reduction Potential) and temperature in industrial processes. It is suitable for steam sterilization and has been developed for applications in the food and pharmaceutical industries.

Applications of ORP Sensor SE-565-ORP

Hygiene and disinfection applications, food and pharmaceutical industries, biotechnology.

Technical Specifications of ORP Sensor SE-565-ORP:

  • ORP Range: -1500mV to +1500mV
  • Temperature Range: 0°C to 135°C
  • Pressure Resistance: Up to 6 bars
  • Temperature Detection: NTC 30 kiloohms
  • Sensor Material: Platinum
  • Reference System: Silver/Chloride Silver, Polymeric Electrolyte
  • Junction: Ceramic (1x)
  • Length: 120 mm / 225 mm
  • Sensor Cap: Memosens technology
  • ATEX Certification: II 1 G Ex ia IIC T3/T4/T6

Conductivity Measurement for Automatic Purging

To reduce the salt content in the cooling system, a purging process is employed, which involves discharging mineral-rich cooling water and supplying low-salinity water to the system. Automatic purging relies on measuring conductivity to indicate the water’s salinity level. The SE 680 toroidal conductivity sensor, made from FDA-approved PEEK material, offers high-precision measurements and a broad measurement range. Due to its Virgin PEEK construction, the sensor is steam sterilizable and features a robust, gapless, and contamination-resistant surface. This sensor is widely used in various applications, including cooling tower monitoring, clean-in-place (CIP) monitoring in the beverage and dairy industries, pharmaceutical applications, wastewater treatment plants, and concentration monitoring for salt solutions, acids, and alkalis.

SE 680 Ring Conductivity Sensor Overview

The SE 680 Ring Conductivity Sensor is a high-precision sensor made from FDA-approved PEEK material. It offers a wide measurement range and is capable of steam sterilization. The sensor is constructed with Virgin PEEK material, providing a seamless and anti-fouling surface without any vulnerable or corrosive areas. Its induction technology remains unaffected by polarization.


  • Compact design
  • Competitive pricing
  • Large measurement range
  • Fast response temperature detection
  • Digital data transmission
  • Complete molded surface
  • Virgin PEEK, FDA type

SE 680 Ring Conductivity Sensor Applications:

  • Freshwater technology
  • Dairy production
  • Brewery operations
  • Soft drink manufacturing
  • Electroplating
  • Air conditioning
  • Online Cleaning-in-Place (CIP) monitoring in the beverage industry
  • Pharmaceutical applications
  • Cooling tower monitoring
  • On-site wastewater treatment plants
  • Concentration monitoring of salt solutions, alkalis, acids, washing machines, and rinsing processes.

Technical Parameters:

  • Cell factor: c ≈ 5.0/cm
  • Installation factor: 1 (adjustable)
  • Measuring range: 0.002 … 2000 mS/cm
  • Error: ± 1 % meas. val. + 0.002 mS/cm, ± 0.02 %/K
  • Materials with process contact: Virgin PEEK, FDA type
  • Materials without process contact: PP-ESD
  • Temperature sensor: Pt1000
  • Response time: T 90 approx. 30 s
  • Process temperature: –10 … +125 °C (see PT diagram)
  • Sterilization: ≤ 5 bar / ≤ 150 °C / ≤ 60 min
  • Ambient temperature: -20 … +60 °C
  • Pressure range P rel: -0.1 … 10 bar (see PT diagram)
  • Surface roughness (process-wetted part): Ra < 0.4 µm
  • Electrical connection: M12 plug, 4-pin; cable length max. 100 m
  • Certificates: FDA CFR 177.2415; material testing acc. to USP IV 121 °C; USP and class VI
  • Explosion protection (SE680X-*******M): IECEx TUN 15.0026 X; Ex ia IIC T6/T4/T3 Ga; TÜV 15 ATEX 154534 X; II 1 G Ex ia IIC T6/T4/T3 Ga
  • Temperature class: T6, T4, T3 (Ambient and process temperature range: -20 °C ≤ Ta ≤ +75 °C, -20 °C ≤ Ta ≤ +125 °C, -20 °C ≤ Ta ≤ +150 °C)

The Advantages of Memosens Technology

Traditional analog sensors are not waterproof, presenting challenges when used in humid environments such as cooling towers. Manufacturers typically encapsulate the connecting cables inside the sensor, making cable detachment necessary when replacing the sensor. Memosens sensors, on the other hand, employ non-contact, 100% moisture-resistant data transmission, eliminating the need for cable detaching. This allows the sensors to be connected underwater, providing greater convenience and ease of use.

Memosens technology also allows for pre-calibration of sensors in ideal laboratory conditions, enabling even untrained personnel to replace sensors on-site. Memosens coupling is compatible with pH/ORP, dissolved oxygen, and conductivity sensors. When paired with the Stratos series transmitters, it significantly reduces calibration, sensor replacement frequency, and the quantity of stocked sensors. This streamlined maintenance approach ultimately lowers personnel costs and enhances the cooling system’s overall lifespan.


Applying pH, ORP, and conductivity sensors in cooling tower monitoring is essential to maintaining efficiency, preventing corrosion, and ensuring water quality and system longevity. By embracing advanced technologies like Memosens, industries can automate monitoring and control processes, reducing maintenance, chemical usage, and unplanned downtime costs. With the combination of Knick’s high-quality sensors and Stratos transmitters, cooling tower operators can optimize their processes, improve productivity, and enhance the overall performance of their cooling systems.