How to Properly Soak the pH Combination Electrode?

The pH electrode must be soaked before use because the pH bulb is a special glass membrane with a very thin hydrated gel layer on its surface. It can only respond well to H+ ions in the solution under sufficiently moist conditions. At the same time, soaking the glass electrode can significantly reduce the asymmetric potential and make it stable. pH glass electrodes can generally be soaked in distilled water or pH4 buffer solution. It is usually better to use pH4 buffer solution; the soaking time ranges from 8 to 24 hours or longer, depending on the thickness of the bulb glass membrane and the degree of electrode aging.

Simultaneously, the liquid junction of the reference electrode also needs to be soaked. If the liquid junction dries out, the liquid junction potential will increase or become unstable. The soaking solution for the reference electrode must be consistent with the external reference solution of the reference electrode, and the soaking time is generally a few hours.

Therefore, for pH combination electrodes, they must be soaked in a pH4 buffer solution containing KCl, so that it can act on both the glass bulb and the liquid junction simultaneously. Special attention is reminded here: because in the past people used single pH glass electrodes and were accustomed to soaking them in deionized water or pH4 buffer solution, they still use this soaking method when using pH combination electrodes later, and even some incorrect pH combination electrode manuals provide such wrong guidance. The direct consequence of this incorrect soaking method is to turn a high-performance pH combination electrode into an electrode with slow response and poor accuracy; the longer the soaking time, the worse the performance, because after long-term soaking, the KCl concentration inside the liquid junction (such as inside the sand core) has been greatly reduced, causing the liquid junction potential to increase and become unstable. Of course, as long as it is re-soaked in the correct soaking solution for several hours, the electrode will still recover.

In addition, pH electrodes cannot be soaked in neutral or alkaline buffer solutions. Long-term soaking in such solutions will cause the pH glass membrane to respond sluggishly.

I. Application Environment Description

Used for environmental water quality monitoring, acid/alkali/salt solutions, chemical reaction processes, and industrial production processes, it can meet the requirements of most industrial applications for online pH measurement.

• Signal output: RS-485 (Modbus RTU).

• Convenient connection to third-party equipment such as PLC, DCS, industrial control computers, general controllers, paperless recorders, or touch screens.

• Dual high-impedance differential amplifier, strong anti-interference, fast response speed.

• Patented pH electrode: the internal reference liquid seeps out extremely slowly from the microporous salt bridge under a pressure of at least 100KPa (1Bar), and its forward seepage lasts for more than 20 months. Such a reference system is very stable, and the electrode life is doubled compared to ordinary industrial electrodes.

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

• IP68 protection level.

II. Technical Performance and Specifications

1. Technical Parameters

III. Use and Maintenance

When measuring with the pH sensor, it should first be cleaned in distilled water (or deionized water) and dried with filter paper to prevent impurities from being brought into the measured liquid. 1/3 of the sensor should be inserted into the measured solution.

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

Check if the wiring terminals are dry. If there is any contamination, please wipe with absolute alcohol and blow dry before use. Long-term immersion in distilled water or protein solutions should be avoided, and contact with silicone grease should be prevented. For sensors used for a long time, the glass membrane may become translucent or have deposits. At this time, it can be washed with dilute hydrochloric acid and rinsed with water. After long-term use, if measurement errors occur, the sensor must be calibrated with the instrument for correction.

When the sensor still cannot perform calibration and measurement after maintenance and care using the above methods, it indicates that the sensor has failed. Please replace the sensor.

FAQ Section

Q1: Can YEX-S1-PH be directly connected to a PLC?
Yes. The sensor outputs standard Modbus RTU signals via the RS-485 bus, which can be directly connected to the serial port module of a PLC that supports this protocol.

Q2: What is the best way to store the electrode?
When the sensor is not in use, it should be cleaned and inserted into a protective sleeve filled with 3mol/L KCl solution. Do not leave it dry.

Q3: How to handle deposits on the glass membrane?
For deposits generated after long-term use, they can be washed with dilute hydrochloric acid (HCl), then rinsed with deionized water and re-activated.

Q4: Why can't it be soaked in neutral or alkaline buffer solutions?
Long-term soaking in neutral or alkaline environments will degrade the ion exchange performance on the glass membrane surface, resulting in a sluggish response.

Q5: What does the IP68 rating of YEX-S1-PH mean?
It means the sensor has a high level of dustproof and waterproof performance and can be fully immersed in water for long-term use under specific pressure.

Q6: How to calibrate the sensor when measurement errors occur?
A two-point calibration method is recommended (e.g., pH 4.00 and pH 9.18). Calibration should be performed in conjunction with the calibration algorithm of the secondary instrument or system software.

Q7: What are the signs of electrode failure?
Electrode failure is determined when the response time significantly exceeds the standard, the slope is below 85%, or the two-point calibration cannot be completed even after routine maintenance.

Q8: Is this sensor suitable for strong acid and strong alkali environments?
The measurement range of YEX-S1-PH is 0-14 pH, which is suitable for most industrial acid and alkali environments. However, for extremely high temperatures or extremely strong oxidizing environments, it is recommended to consult for technical selection.

Summary

The YexSensor YEX-S1-PH industrial-grade pH sensor provides system integrators with a monitoring component that combines high reliability with a standard digital interface. By understanding the hydrated layer chemical characteristics behind it and implementing correct soaking maintenance standards, integrators can significantly increase the online uptime of the monitoring system, reduce after-sales costs, and deliver a more accurate and stable value closed loop for industrial customers.