RS485 4-20mA Digital pH Sensor for General Water Agricultural Water-fertilizer Machinery System

RS485 4-20mA Digital pH Sensor for General Water Agricultural Water-fertilizer Machinery System

>>Overview

The digital pH sensor is suitable for general industrial processes. Its double salt bridge design and dual-layer permeable interface resist medium backflow. The ceramic porous electrode exudation interface is less prone to clogging, making it ideal for common water quality monitoring. A PTFE large-ring diaphragm ensures electrode durability, and it is primarily used in agricultural water-fertilizer machinery systems.

>>Feature

• ‌Spherical sensing bulb‌: Enlarges sensitive areas for faster response and stable signals.
• ‌PA+GF housing‌: Withstands high temperatures (0–60°C).
• ‌Quad-core shielded cable‌: High-quality dedicated wiring ensures precise signal transmission.

>>Technical Parameter

pH Range: 2-12 pH
pH Zero Point: 7.00±0.25
Temperature Range: 0-80°C
Output: RS485 & 4-20mA
Pressure Resistance: 0-0.3MPa
Temperature Sensor: None
Housing Material: PA+GF
Membrane Resistance: <500MΩ
Reference System: Ag/AgCl/KCl
Liquid Junction: Ceramic Sand Core
Electrolyte Solution: KCl
Dual Salt Bridge System: Yes
Connection Thread: NPT 3/4"

>>Principle

The core theory of pH electrode measurement is the Nernst equation. The sensor used in potentiometric analysis is called a galvanic cell. A galvanic cell is a system that converts chemical reaction energy into electrical energy. The voltage of this cell is referred to as the electromotive force (EMF). This EMF consists of two half-cells. One half-cell is the measuring sensor, whose potential is related to the activity of specific ions; the other is the reference half-cell, often called the reference sensor, which is typically connected to the measurement solution and the instrument.

ORP (Oxidation-Reduction Potential) is a critical indicator of water quality. While it cannot independently determine water quality, it reflects the ecological environment of aquatic systems by integrating other water quality parameters.

In water, each substance has its unique redox properties. Simplistically, this can be understood as: at a microscopic level, different substances possess varying oxidation-reduction capacities. These substances interact to form an overall macroscopic redox characteristic. ORP reflects the collective redox behavior of all substances in the solution. A higher ORP indicates stronger oxidizing capacity, while a lower ORP suggests weaker oxidizing capacity. A positive potential signifies oxidizing properties, whereas a negative potential indicates reducing properties.

>>Installation Diagram

Before use, unscrew the electrode protective cap and install it with the appropriate mounting bracket or accessories.

‌1. Sidewall Installation‌: Ensure the interface tilt angle exceeds 15 degrees.

‌2. Top Flange Installation‌: Note flange dimensions and electrode insertion depth.

‌3. Pipe Installation‌: Consider pipe diameter, flow velocity, and pressure.

‌4. Flow-Through Installation‌: Monitor flow velocity and pressure.

‌5. Submersion Installation‌: Adjust bracket length as needed.

>>Electrode Maintenance and Care

○ Before use, unscrew the protective cap and immerse the electrode bulb and liquid junction in the sample.

○ If salt crystals form near the electrode tip or inside the cap due to electrolyte evaporation, rinse with water. This indicates normal dialysis membrane function.

○ Check for air bubbles in the glass bulb by shaking the electrode vertically.

○ Keep the glass membrane hydrated for fast response. After measurement or calibration: Rinse the electrode thoroughly. Add storage solution (3 mol/L KCl) to the protective cap.

○ Ensure terminal connections remain dry. Clean with anhydrous alcohol if contaminated.

○ Avoid prolonged immersion in distilled water, protein solutions, or contact with silicone grease.

○ For aged electrodes with cloudy membranes or deposits, soak in 10% HCl, then rinse.

○ Regularly clean and calibrate the electrode. If calibration fails after maintenance, replace the electrode.

>>Lifespan

Under normal conditions with proper maintenance, electrodes last over 12 months. Even unused electrodes have a shelf life of 12–24 months (if stored correctly). Exposure to strong acids, bases, high temperatures, or corrosive liquids shortens lifespan. Electrodes are consumables and generally not covered by warranty.

>>Electrode Calibration

○ Use fresh pH/ORP standard buffer solutions of appropriate concentrations.

○ Remove the protective cap and rinse the electrode with distilled water.

○ Set the instrument to calibration mode (refer to the instrument manual for details).

○ After calibration, measure actual samples.