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How to measure the pH value of a liquid
The measurement of liquid pH values is a critical process for ensuring process safety, compliance with environmental regulations, and product quality across industries such as agriculture, sewage treatment, chemical manufacturing, printing and dyeing, papermaking, pharmaceuticals, electroplating, and environmental protection.
While conventional pH measurement methods often require complex setup procedures or specialized calibration equipment, the RIKA SENSOR’s RK500-12 pH Sensor facilitates this process through its user-eccentric operational design, stable performance, and broad environmental adaptability.
1.Preparatory Phase: Tool Assembly and Sensor Model Selection
1.1 Required Equipment and Materials
- One RK500-12 pH Sensor (selected based on application-specific needs).
- 3mol/L potassium chloride (KCl) solution or saturated KCl solution (for sensor storage and electrode pretreatment).
- Optional installation bracket (1m in length, compatible with NPT3/4 installation threads; refer to the Installation & Fixed section for specifications).
- Data acquisition device (compatible with the sensor’s RS485 or 4-20mA output interfaces).
- Clean rinsing water (for post-measurement electrode cleaning to remove residual contaminants).
1.2 Scientific Selection of the RK500-12 Model
The RK500-12 pH Sensor is available in multiple configurations, each engineered to address specific liquid characteristics, temperature ranges, and installation scenarios.
|
Type |
Details |
Application |
|
A1 |
Small immersion type,direct cable |
Conventional water,sewage,nutrient solution,etc |
|
A2 |
Small immersion type,direct cable |
Industrial water,seawater,environmental protection,etc |
|
B1 |
PG13.5 thread installation,M8 connector |
Conventional water,sewage,nutrient solution,etc |
|
B2 |
PG13.5 thread installation,M8 connector |
Industrial water,seawater,environmental protection,etc |
|
B3 |
PG13.5 thread installation,M8 connector |
High temperature environment(>80℃) |
|
C1 |
Upper:NPT3/4 thread,lower:NPT3/4 thread,direct cable |
Conventional water,river water,etc |
|
C2 |
Upper:NPT3/4 thread,lower:NPT3/4 thread,direct cable |
Industrial water,seawater,environmental protection,etc |
|
C3 |
Upper:NPT3/4 thread,lower:NPT3/4 thread,direct cable |
High temperature environment(>80℃) |
|
D1 |
Upper:NPT3/4 thread,lower:NPT3/4 thread,waterproof connector |
Conventional water,river water,etc |
|
D2 |
Upper:NPT3/4 thread,lower:NPT3/4 thread,waterproof connector |
Industrial water,seawater,environmental protection,etc |
|
D3 |
Upper:NPT3/4 thread,lower:NPT3/4 thread,waterproof connector |
High temperature environment(>80℃) |
2. Step-by-Step Protocol for Liquid pH Measurement
The RK500-12 pH Sensor eliminates the need for specialized calibration instruments, but adherence to the following standardized protocol is critical for ensuring measurement precision and reproducibility.
Step 1: Electrode Pretreatment
- For sensors not in recent use, first remove the protective cap from the electrode to expose the sensitive glass film.
- Immerse the electrode in 3mol/L KCl solution or saturated KCl solution for 30 minutes to activate the sensitive glass film and restore electrode performance. Critical note: Immersion in distilled water, deionized water, or low-ion-concentration tap water is strictly prohibited, as this may irreversibly damage the electrode.
Step 2: Proper Sensor Installation
The RK500-12 supports multiple installation methods; the selection should be based on the type of liquid container (e.g., tank, pipeline, flow channel), and the following installation criteria must be observed to avoid measurement errors:
|
Installation Method |
Key Operational Requirements |
|
Immersion Installation |
Mount the sensor above the sediment layer (to prevent fouling of the electrode) and ensure complete submersion of the sensitive region. Use the optional 1m bracket for stable positioning. |
|
Pipeline Installation |
Install the sensor at a 0°/360° angle; avoid areas with non-uniform liquid flow (e.g., pipeline bends or dead zones) to prevent inconsistent readings. |
|
Sidewall/Top Mounting |
Position the electrode to face the direction of liquid flow; do not install it horizontally-ensure there is a 15° angle with the horizontal direction. Avoid recessed installation (prone to deposit accumulation, requiring more frequen cleaning). |
- Provide the sensor with a DC power supply of 7–30 V (power consumption not exceeding 0.15W).
- Connect the sensor to the data acquisition device via its RS485 or 4-20mA output interface. Ensure all connections are secure to minimize signal interference—note that the sensor incorporates internal signal isolation technology to enhance anti-interference capabilities.
Step 4: Data Logging and Analysis
The sensor delivers performance metrics that meet industrial precision requirements:
- Measurement range: 0–14 pH (covers all practical liquid pH scenarios).
- Resolution: 0.01 pH (enables detection of subtle pH fluctuations).
- Accuracy: ±0.01 pH (ensures reliability for critical applications such as pharmaceutical water quality control).
Log the acquired data using the data acquisition device, and compare results against industry-specific standards (e.g., a pH range of 5.5–6.5 for certain agricultural nutrient solutions).
Step 5: Post-Measurement Sensor Maintenance
- Remove the sensor from the liquid and rinse the electrode thoroughly with clean water to eliminate residual contaminants.
- For short-term storage (imminent reuse), keep the electrode moist with a small volume of KCl solution. For long-term storage, immerse the electrode in 3mol/L KCl solution—dry storage is strictly forbidden.
3. Critical Precautions for Ensuring Measurement Accuracy
To mitigate measurement errors and extend the sensor’s service life, the following precautions must be observed, as derived from the RK500-12’s product specifications:
3.1 Environmental Factor Control
-
Temperature constraints: Do not operate the sensor beyond its specified temperature range (e.g., 0–60℃ for Model A1, 0–100℃ for Model B3). While the sensor integrates thermal resistance for temperature compensation (per the Features section), extreme temperatures may still degrade performance.
-
Pressure constraints: Adhere to the sensor’s maximum working pressure (e.g., 0.6MPa for Model A1, 1MPa for Model B2) to prevent structural damage to the electrode.
3.2 Routine Cleaning and Maintenance
-
Perform routine electrode cleaning every 3–6 months using tap water. For heavy contamination:
-
Inorganic contaminants: Immerse the electrode in 0.1mol/L hydrochloric acid (HCl) or sodium hydroxide (NaOH) solution for several minutes, followed by thorough rinsing with distilled water.
-
Organic contaminants: Clean the electrode with alcohol or acetone, then rinse with distilled water to remove residual solvents.
-
Replace the electrode if the sensitive glass film is cracked, scratched, or if the sensor’s response time significantly increases (indicating electrode degradation).
3.3 Mitigation of Common Operational Errors
-
Never operate the sensor without removing the electrode’s protective cap, as this blocks contact between the sensitive film and the target liquid.
-
Ensure electrical connectors (e.g., M8 or M16 interfaces) remain dry during operation.
4. Conclusion
Liquid pH measurement is streamlined through the RK500-12 pH Sensor, which combines user-centric design, broad environmental adaptability, and reliable performance.
By selecting the appropriate sensor model, adhering to standardized installation and maintenance protocols, and implementing the precautions outlined herein, users can achieve accurate, reproducible pH measurements across agriculture, sewage treatment, chemical manufacturing, and aquaculture applications.
For additional technical details, welcome to visit RIKA SENSOR’s official website:rikasensor.com. We hope you find value in the article and Rika products.
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