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In industrial production, even minor deviations in pH levels can lead to significant consequences. A slight imbalance in food processing may cause spoilage, while improper pH control in water treatment could pose public health risks. pH measurement plays a critical role in industrial processes, and the performance of pH sensors—the core component of pH meters—directly determines the accuracy and reliability of measurements. Currently, industrial pH meters primarily utilize two technologies: glass pH sensors and ISFET pH sensors. Each has distinct advantages and limitations. How should industrial users choose between them? This article provides an in-depth comparison to guide decision-making.

Glass pH sensors are a long-established and widely used technology for pH measurement. Their core structure consists of a specialized glass bulb and a reference electrode. The bulb contains a solution with a specific ion concentration, while its outer surface interacts with the test solution. The glass membrane selectively allows hydrogen ions to pass, creating a potential difference between the inner and outer surfaces. The reference electrode provides a stable reference potential, and the pH meter calculates the pH value based on the potential difference between the glass bulb and the reference electrode, using the Nernst equation.

The primary advantage of glass pH sensors lies in their high sensitivity. The glass membrane's strong selectivity for hydrogen ions enables precise detection of even minor pH changes, making these sensors ideal for applications requiring high accuracy, such as pharmaceuticals, biotechnology, and food and beverage production.

ISFET (Ion-Sensitive Field-Effect Transistor) pH sensors represent a newer technology based on semiconductor principles. They utilize a metal oxide layer as an ion-sensitive membrane. When this membrane contacts the test solution, hydrogen ions adsorb onto its surface, altering the charge distribution and affecting the semiconductor's conductivity. The pH meter measures this conductivity change to determine the pH value.

The standout feature of ISFET sensors is their durability. Unlike fragile glass bulbs, the metal oxide membrane is highly resistant to corrosion, abrasion, and physical damage. This makes ISFET sensors better suited for harsh industrial environments, including wastewater treatment, chemical processing, and mining operations.

To facilitate comparison, we evaluate both technologies across five critical dimensions:

• Sensitivity: Glass sensors outperform ISFET sensors due to their superior hydrogen ion selectivity, delivering more accurate measurements in precision-critical applications.
• Durability: ISFET sensors excel in harsh conditions, as their solid-state design resists breakage, high pressures, and corrosive substances.
• Maintenance: ISFET sensors require less frequent calibration and cleaning compared to glass sensors, which are prone to membrane fouling.
• Response Time: ISFET sensors react faster to pH changes, making them preferable for real-time monitoring in dynamic processes.
• Interference: Glass sensors are more susceptible to interference from other ions (e.g., sodium), while ISFET sensors offer greater reliability in complex solutions.

Choosing between glass and ISFET pH sensors depends on several factors:

• Precision Requirements: Opt for glass sensors when high accuracy is paramount.
• Environmental Conditions: ISFET sensors are better suited for rugged or corrosive settings.
• Maintenance Constraints: ISFET sensors reduce upkeep demands.
• Speed Needs: ISFET sensors provide quicker responses for time-sensitive processes.
• Solution Composition: ISFET sensors handle complex mixtures with fewer errors.

By carefully weighing these factors, industrial users can select the optimal pH sensor for their specific needs, ensuring reliable measurements and operational efficiency.