1. Product Introductions

 The PH Sensor is a digital sensor featuring an easy-to-integrate RS485 communication interface and standard Modbus protocol, It is equipped with a corrosion-resistant housing,IP68 protection rating, suitable for operation in various harsh working environments;

 Select an industrial-grade combination electrode with a double-junction reference electrode design for prolonged service life;

 Equipped with a built-in PT1000 temperature sensor and compensation algorithm, achieving an accuracy of ±0.1℃;

2. Operation Principle
The glass electrode method for measuring the pH of water samples uses a saturated calomel electrode (SCE) as the reference electrode and a glass electrode as the indicator electrode.These electrodes form an electrochemical cell with the water sample, and the electromotive force (EMF) of the cell is measured by a pH meter, which directly displays the pH value.This method is accurate, rapid, and minimally affected by interference from factors such as water color, turbidity, colloidal substances, oxidants, reductants, and salinity.

3. Electrical Connection

The cable is a 4-core twisted-pair shielded wire with the following pinout:

 Red wire: Power supply (12–24 VDC)
 Black wire: Ground (GND)
 White wire: 485B
 Blue wire: 485A

Before energizing the device, thoroughly verify the wiring sequence to prevent damage resulting from incorrect connections.

Given that the cables may be submerged in water (including seawater) or exposed to air for extended periods, they must possess corrosion-resistant properties. Additionally, all connection points must undergo waterproof sealing to ensure long-term reliability.

4. Maintenance and Servicing

4.1 Usage and Maintenance

 When using a pH sensor for measurement, it should first be thoroughly cleaned in distilled water (or deionized water), then blotted dry with filter paper to prevent impurities from being introduced into the solution being measured. ⅓ of the sensor should be inserted into the solution during measurement.

 When the sensor is not in use, it should be cleaned and inserted into a container filled with a 3.5 mol/L potassium chloride (KCl) solution.

 Check whether the terminals are dry. If contaminated, clean them with anhydrous alcohol and dry thoroughly before use. Avoid prolonged immersion in distilled water or protein solutions, and prevent contact with silicone-based oils. For sensors with extended use, if the glass membrane becomes translucent or accumulates deposits, wash with dilute hydrochloric acid followed by water rinsing. When measurement errors occur due to prolonged sensor usage, calibrate with the corresponding instrument.If calibration and measurement remain impossible after performing the above maintenance and care procedures, this indicates that the sensor has failed and should be replaced.

pH Reference Table for Standard Buffer Solutions

5. Sensor Calibration

a)Zero Point Calibration
Measure 250 mL of distilled water using a measuring cylinder and pour it into a beaker, Add one packet of pH 6.86 calibration powder. Stir thoroughly with a glass rod until the powder is completely dissolved to prepare a pH 6.86 solution. Immerse the sensor into the solution and wait 3–5 minutes for the reading to stabilize, verify if the displayed value is 6.86, If not, perform zero-point calibration (refer to the appendix for calibration instructions)

b)Slope Calibration
 For Acidic Solutions: Measure 250 mL of distilled water using a measuring cylinder and pour it into a beaker, Add one packet of pH 4.00 calibration powder. Stir thoroughly with a glass rod until the powder is completely dissolved to prepare a pH 4.00 solution. Immerse the sensor into the solution and wait 3–5 minutes for the reading to stabilize. Verify if the displayed value is 4.00, If not, perform slope calibration (refer to the appendix for calibration instructions)

 For alkaline solution: Measure 250 mL of distilled water using a measuring cylinder and pour it into a beaker, Add one packet of pH 9.18 calibration powder. Stir thoroughly with a glass rod until the powder is completely dissolved to prepare a pH 9.18 solution. Immerse the sensor into the solution and wait 3–5 minutes for the reading to stabilize. Verify if the displayed value is 9.18, If not, perform slope calibration (refer to the appendix for calibration instructions)