NBL-CL-406 Industrial Residual Chlorine Sensor: For Drinking Water, Swimming Pool Water Quality Monitoring

Real-time Precise Monitoring: NiuBoL NBL-CL-406 Constant Voltage Online Residual Chlorine Sensor

— No Consumables, Long-term Stability, Specially Designed for High-Standard Water Quality Monitoring Projects

In secondary water supply, swimming pool disinfection, and industrial water treatment processes, fluctuations in residual chlorine content directly affect sterilization effectiveness and water safety. However, traditional membrane or DPD colorimetric residual chlorine sensors often face challenges such as membrane damage, electrolyte drying, or frequent reagent replenishment, bringing a heavy burden to later on-site operation and maintenance.

The NiuBoL NBL-CL-406 series sensor adopts innovative constant voltage technology. It abandons fragile gas-permeable membranes and measures the reduction current of hypochlorous acid (HClO) in water by maintaining a constant electrode potential, achieving zero-maintenance and high-stability online monitoring.

Maintenance-free Design: The constant voltage principle requires no replacement of membranes or electrolyte, significantly reducing long-term ownership costs.

Excellent Response: T90 response time is less than 90 seconds, capturing subtle water quality fluctuations and ensuring timely feedback from disinfection dosing systems.

Engineering-grade Integration: Standard RS485 output perfectly compatible with central control PLC and various smart water monitoring gateways.

NBL-CL-406 Series Online Residual Chlorine Sensor Core Overview

The NiuBoL NBL-CL-406 series is a digital residual chlorine sensor designed for industrial and municipal environments. The product includes two versions: NBL-CL-406-A (economical) and NBL-CL-406-S (industrial enhanced). The range covers 0～2 mg/L to 0～20 mg/L, with accuracy up to ±5% of reading, meeting diverse needs from laboratory-level precision to industrial-grade robustness.

For system integrators, the core value of the NBL-CL-406 lies in its "highly reliable digital output". The sensor has a built-in signal processing circuit and directly outputs standard Modbus RTU signals. The supporting professional flow cell design ensures a stable flow velocity in the measurement environment, providing continuous, reliable data support for water plants, pumping stations, and industrial parks.

NBL-CL-406 Series Online Residual Chlorine Sensor Core Technical Advantages

1. Constant Voltage Technology Principle: Guarantee of Stability
   Compared with traditional polarographic methods, the constant voltage method used by NiuBoL maintains a constant potential difference on the electrode surface during measurement. Residual chlorine molecules in water undergo electrochemical reaction directly on the electrode surface. The biggest advantage of this method is that it requires no frequent calibration and has no consumable consumption, offering extremely high reproducibility in water bodies with relatively stable pH.

2. Industrial-grade Housing Materials, Adapting to Various Conditions
   The NBL-CL-406 series offers diverse material options. NBL-CL-406-A uses a POM + ABS combination for lightweight durability, while NBL-CL-406-S uses 316L stainless steel for stronger impact resistance and electromagnetic interference resistance. The overall IP68 protection rating ensures that core electronic components remain safe even in humid pump room environments or in case of accidental flooding.

3. Built-in Pt1000 Automatic Temperature Compensation
   The chemical activity of residual chlorine is significantly affected by temperature. NiuBoL integrates a high-precision Pt1000 temperature sensor inside the sensor to monitor water temperature in real time and perform automatic algorithmic compensation. Whether in high-temperature circulating cooling water in summer or cold tap water plants in northern winter, the sensor can output corrected standard concentration values.

4. Digital Anti-interference Design
   The sensor uses twisted shielded wire design internally and transmits signals via RS485 digital signals. Compared with traditional analog current signals, digital transmission has extremely strong anti-electromagnetic interference capability. Even in sites densely populated with large electrical equipment such as frequency converters and pumps, data remains lossless and stable.

NBL-CL-406 Series Online Residual Chlorine Sensor Technical Performance Specifications

NBL-CL-406 Series Online Residual Chlorine Sensor Typical Application Scenarios

• Municipal Tap Water Supply Network: Installed in water supply pumping stations and terminal pipe networks to ensure residual chlorine content during transportation meets national hygiene standards and prevents bacterial growth.

• Swimming Pools and Landscape Water Treatment: Linked with dosing pumps for real-time closed-loop control, ensuring sterilization effect while avoiding excessive residual chlorine that may irritate human skin and mucous membranes.

• Food and Beverage Filling: Monitoring residual chlorine in rinsing and production water to prevent residual chlorine in water from affecting food taste and safety.

• Industrial Circulating Cooling Water: Monitoring bactericide concentration in circulating water systems to effectively control biological slime deposition and protect heat exchanger equipment from corrosion.

Installation and Electrical Connection

Key Points for Flow Cell Installation

• Flow Rate Control: Inlet flow rate is recommended to be stable at 30-60 L/h. Too fast flow rate will scour the electrode and cause unstable readings; too slow flow rate will cause delayed response.

• Position Requirements: The sensor should be installed near the water inlet, avoiding proximity to the water outlet, to ensure the electrode front end is always in steadily flowing liquid.

Wiring Instructions

The cable uses 5-core twisted shielded wire with the following specific wiring sequence:

• Red wire: Power positive (12～24V DC)

• Black wire: Power ground (GND)

• Blue wire: RS485-A

• Green wire: RS485-B

• Yellow wire: Current output (connect to the corresponding port if 4-20mA module is configured; leave floating and insulate if not in use)

Expert Advice: During installation and wiring, please keep signal lines at least 20cm away from power lines (such as water pump cables), and perform waterproof treatment on all exposed wiring points.

FAQ

Q1: What is the difference between the constant voltage principle of NiuBoL NBL-CL-406 and traditional residual chlorine meters?

A: Traditional residual chlorine meters usually require membranes and electrolyte, resulting in high maintenance workload and expensive follow-up consumables. The NBL-CL-406 adopts the constant voltage method with a robust structure and no consumable replacement, making it more suitable for industrial online continuous monitoring.

Q2: Can the sensor be installed and used directly upon receipt?

A: New electrodes or electrodes that have been stored for a long time require "activation". Please place the sensor in tap water for 24 hours before calibration and use to ensure the chemical activity of the electrode surface.

Q3: Why must the flow cell be used for installation?

A: Residual chlorine sensors are very sensitive to flow rate. The flow cell provides a stable pressure and flow environment (recommended 30-60 L/h) to avoid the negative impact of air bubbles and turbulence on measurement results.

Q4: Is the sensor measurement affected by pH value?

A: The constant voltage method measures HClO. It performs best in the pH 4～9 range. If the on-site water pH fluctuates dramatically, it is recommended to link with a pH sensor for compensation to obtain extremely high accuracy.

Q5: What to do if the reading shows obvious drift?

A: First check whether the electrode front end has dirt or attachments and rinse gently with clean water. If still inaccurate, perform zero point calibration in chlorine-free water according to the manual and use data from a standard DPD colorimetric meter for slope calibration.

Q6: What is the maximum cable length supported for customization?

A: The standard cable is 5 meters. Since RS485 digital transmission is used with low signal attenuation, we can customize shielded cables of 10 meters, 20 meters or even longer according to your project requirements.

Q7: Can this sensor measure total chlorine?

A: The NBL-CL-406 is calibrated for residual chlorine (hypochlorous acid HClO) by default. If you need to measure total chlorine or other chlorides, please consult NiuBoL technical support for specific model recommendations.

Q8: What is the warranty period?

A: NiuBoL provides a one-year quality guarantee from the date of sale. Every sensor undergoes 72-hour aging and stability testing before leaving the factory to ensure 100% qualification.

Conclusion: Helping Your Smart Water Project Achieve Excellent Performance

In high-demand B2B water treatment projects, equipment downtime and maintenance costs often exceed procurement costs. The NiuBoL NBL-CL-406 provides integrators and engineering contractors with an ideal "high-precision, low-maintenance" choice through innovative constant voltage technology and a robust digital architecture.

Are you looking for a high-stability residual chlorine detection solution for your drinking water monitoring or swimming pool water quality system?

Contact NiuBoL immediately to obtain in-depth technical selection suggestions and the latest quotation tailored to your project conditions.

NBL-CL-406 Series Online Water quality Residual Chlorine Sensor Data Sheet

NBL-CL-406 Series Online Water quality Residual Chlorine Sensor.pdf