NBL-WQ-PH Online Water Quality pH Sensor

Online Water Quality pH Sensor NBL-WQ-PH

Used for environmental water quality monitoring, acidic/alkaline/saline solutions, chemical reaction processes, and industrial production processes, meeting the requirements of online pH measurement for most industrial applications. Signal output: RS-485 (Modbus/RTU protocol). Convenient connection to third-party devices such as PLCs, DCS systems, industrial control computers, general controllers, paperless recorders, or touch screens. High-input impedance differential amplifier with strong anti-interference capability and fast response. Patented pH probe, the internal reference solution slowly seeps through the microporous salt bridge under a pressure of at least 100 kPa (1 Bar), and its positive leakage continues for more than 20 months. This reference system is highly stable, and the electrode service life is extended several times compared with conventional industrial electrodes. Easy installation: 3/4 NPT pipe thread for easy immersion installation or installation in pipes and tanks. Protection rating IP68.

Technical Specifications of Online Water Quality pH Sensor

1. Application environment description

This sensor is used for environmental water quality monitoring, acidic/alkaline/saline solutions, chemical reaction processes, and industrial production processes. It meets the requirements of online pH measurement for most industrial applications.

- Signal output: RS-485 (Modbus RTU protocol)

- Easy connection to PLC, DCS, industrial control computers, general controllers, paperless recorders, touch screens, and other third-party devices.

- High-input impedance differential amplifier with strong anti-interference capability and fast response.

- Patented pH electrode: the internal reference solution slowly leaks through a microporous salt bridge under a pressure of at least 100 kPa (1 Bar), and the positive leakage continues for more than 20 months. This reference system is highly stable, and the electrode life is extended several times compared with conventional industrial electrodes.

- Easy installation: 3/4 NPT thread, suitable for immersion installation or installation in pipes and tanks.

- Protection rating IP68.

2. Installation

Note: The sensor must not be installed upside down or horizontally, and must be installed with an inclination of at least 15 degrees.

3. Electrical connection

The cable is a 4-core shielded twisted wire with the following pin definition:

- Red wire – Power supply (12–24 VDC)

- Black wire – Ground (GND)

- Blue wire – 485A

- White wire – 485B

Before powering on, carefully check the wiring sequence to avoid unnecessary damage caused by incorrect connections.

Wiring instructions: Since the cable is frequently immersed in water (including seawater) or exposed to air, all wiring points require waterproof treatment. User cables must have a certain level of corrosion resistance.

4. Maintenance and care

4.1 Use and maintenance

During measurement, the pH sensor should first be cleaned with distilled water (or deionized water) and dried with filter paper to avoid contamination of the measured solution. One-third of the sensor should be immersed in the solution.

When not in use, the sensor should be cleaned and inserted into a protective cap filled with 3 mol/L potassium chloride solution or placed in a container filled with the same solution.

Check whether the terminal connections are dry. If contaminated, clean with anhydrous alcohol, dry, and then use. Avoid long-term immersion in distilled water or protein solutions, and prevent contact with silicone oil or grease. If the sensor is used for a long time, the glass membrane may become semi-transparent or develop deposits. In this case, clean with diluted hydrochloric acid and rinse with water. When long-term use causes measurement errors, the sensor should be calibrated with an instrument.

If calibration or measurement cannot be performed even after the above maintenance procedures, it indicates that the sensor has failed and should be replaced.

5. Calibration

Note: The sensor has been calibrated before leaving the factory. Unless the measurement error exceeds the limit, avoid arbitrary recalibration.

5.1 Zero calibration

Take 250 mL of distilled water in a graduated cylinder, pour it into a beaker, add one packet of pH 6.86 calibration powder, and stir with a glass rod until completely dissolved. Prepare a pH 6.86 solution. Place the sensor in the solution, wait 3–5 minutes until the value stabilizes, and check whether the displayed value is 6.86. If not, zero calibration is required. Refer to the appendix for calibration instructions.

5.2 Slope calibration

- Acid solution: Take 250 mL of distilled water in a graduated cylinder, pour it into a beaker, add one packet of pH 4.00 calibration powder, and stir until fully dissolved. Prepare a pH 4.00 solution. Place the sensor in the solution, wait 3–5 minutes until the value stabilizes, and check whether the displayed value is 4.00. If not, slope calibration is required. Refer to the appendix for calibration instructions.

- Alkaline solution: Take 250 mL of distilled water in a graduated cylinder, pour it into a beaker, add one packet of pH 9.18 calibration powder, and stir until fully dissolved. Prepare a pH 9.18 solution. Place the sensor in the solution, wait 3–5 minutes until the value stabilizes, and check whether the displayed value is 9.18. If not, slope calibration is required. Refer to the appendix for calibration instructions.

NBL-WQ-PH Online Water Quality pH Sensor Datasheet.pdf

NBL-WQ-PH Online Water Quality pH Sensor.pdf