PHG-206A Online Water Quality PH Sensor

Used for environmental water quality monitoring, acid/alkali/salt solution, chemical reaction process and industrial production process, it can meet 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 PLC, DCS, industrial control computers, general-purpose controllers, paperless recording instruments or touch screens. Dual high-impedance differential amplifier with strong anti-interference and fast response. The patented pH probe, the internal reference solution oozes extremely slowly from the microporous salt bridge at a pressure of at least 100 kpa (1 Bar), and its forward bleed continues for more than 20 months. Such a reference system is very stable and the electrode life is extended by a factor of two compared to conventional industrial electrodes. Easy to install: 3/4 NPT pipe thread for easy submersible installation or installation in pipes and tanks. IP68 protection grade.

Water Quality PH Sensor Technical Specifications

1. Application Environment Description

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

- Signal Output: RS-485 (Modbus RTU)  

- Easy connection to PLCs, DCS, industrial control computers, general controllers, paperless recorders, touchscreens, and other third-party devices.  

- Dual high-impedance differential amplifier with strong anti-interference and fast response.  

- Patented pH electrode, the internal reference liquid slowly leaks from the microporous salt bridge under at least 100KPa (1Bar) pressure, with the positive leakage continuing for over 20 months. This reference system is highly stable, and the electrode's lifespan is extended multiple times compared to ordinary industrial electrodes.  

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

- IP68 Protection Level.

2.Installation  

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

3.Electrical Connection  

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

- Red wire – Power supply (12-24VDC)  

- Black wire – Ground (GND)  

- Blue wire – 485A  

- White wire – 485B  

Before powering on, check the wiring sequence carefully 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 should have a certain level of corrosion resistance.

4. Maintenance and Care

1. Use and Maintenance  

When measuring, the pH sensor should first be cleaned with distilled water (or deionized water) and dried with filter paper to prevent impurities from contaminating the measured solution. One-third of the sensor should be immersed in the solution.  

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

Check if the terminal connections are dry. If they are soiled, clean with anhydrous alcohol, dry, and then use. Avoid long-term immersion in distilled water or protein solutions, and prevent contact with silicone oils or fats. If the sensor is used for a long time, the glass membrane may become semi-transparent or accumulate deposits. In this case, clean with diluted hydrochloric acid and rinse with water. When the sensor has been in use for a long time and measurement errors occur, it should be calibrated with an instrument.

When maintenance and care methods mentioned above cannot calibrate or measure the sensor properly, it indicates the sensor has failed and should be replaced.

5. Calibration  

Note: The sensor has already been calibrated before leaving the factory. Unless it exceeds the measurement error, avoid calibrating it casually.  

a) Zero Calibration  

Take 250mL 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 the powder is completely dissolved. Prepare a solution of pH=6.86. Place the sensor in the solution, wait for 3-5 minutes until the value stabilizes, and check if the displayed value is 6.86. If not, zero calibration is needed. Please refer to the instructions in the appendix for the calibration process.  

b) Slope Calibration  

- Acidic Solution: Take 250mL of distilled water in a graduated cylinder, pour it into a beaker, add one packet of pH=4.00 calibration powder, and stir with a glass rod until the powder is completely dissolved. Prepare a solution of pH=4.00. Place the sensor in the solution, wait for 3-5 minutes until the value stabilizes, and check if the displayed value is 4.00. If not, slope calibration is required. Please refer to the instructions in the appendix for the calibration process.  

- Alkaline Solution: Take 250mL of distilled water in a graduated cylinder, pour it into a beaker, add one packet of pH=9.18 calibration powder, and stir with a glass rod until the powder is completely dissolved. Prepare a solution of pH=9.18. Place the sensor in the solution, wait for 3-5 minutes until the value stabilizes, and check if the displayed value is 9.18. If not, slope calibration is required. Please refer to the instructions in the appendix for the calibration process.