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There are several ways to classify automatic pH controllers. They can be categorized based on working principle, configuration, application, or industry.
Here are the pH controllers categorized according to their working principle:
Sensors with pH glass electrodes
These automatic instruments use a glass electrode to measure pH values. A measurement glass electrode is sensitive to hydroxide ions in alkaline environments and hydrogen ions in acidic conditions. It produces a voltage in the millivolt range corresponding to the solution's pH. The millivolt value is fully converted into a pH value by the pH meter using the Nernst equation. The pH controller then uses the obtained pH value feedback to control the addbacks of acid and alkali automatically. This way, the solution is maintained at the optimal pH value.
Non-glass electrode pH sensors
These are beneficial in situations where glass electrodes cannot be used. These automatic pH controllers use ion-sensitive technology and combination electrodes instead of glass pH electrodes.
Digital automatic pH controllers
These use digital displays and offer benefits such as ease of reading, user-friendliness, high accuracy, and reliability. Digital controllers automatically modify the solution's pH value using advanced microprocessors, which retrieve the optimal pH value through inputs. These controllers usually include extra features, such as alarms, data logging, or automatic calibration. Users will especially appreciate the digital versions, as their advanced software and hardware increase their dependability and efficiency.
Analog automatic pH controllers
These are older and less effective than digital ones. They are simple to use and cost less than digital ones. However, they are not very accurate, and parameter settings are often adjusted manually. Digital controllers can automatically detect optimal parameter values and adjust them, while analog controllers must be set by hand. Because of these distinctions, analog pH controllers are appropriate for less demanding environments.
Automatic pH controllers for the aquaculture industry
The aquaculture industry uses automatic pH controllers to help maintain the water within pH 6-8 for fish farming. Specific fish species, such as tilapia, catfish, and trout, have different pH preferences within that range. Acidic or alkaline water out of that pH range is dangerous to fish as it can cause stress or even death. pH controllers automatically adjust the water's pH by adding acid or alkaline chemicals. They also add chemical sterilizers in case of a bacterial outbreak.
Automatic pH controllers for the agriculture industry
The agriculture industry uses automatic pH controllers when practicing hydroponics and cultivating crops in soil with a highly acidic or alkaline substrate. They help maintain the nutrient solution pH within 5.5-6.5, the ideal range for nutrient absorption. This helps crops to grow healthy and roots strong. Automatic pH controllers also help keep the water within the pH range for citrus fruits and coffee. These crops require water within the range to maintain quality and flavor. The agriculture industry also relies on automatic pH controllers for its fertilization and wastewater treatment processes.
Automatic pH controllers for the beverage industry
Beverage manufacturers measure beverage quality using pH value. Therefore, they need to maintain it within a specific range using automatic pH controllers. For instance, coffee and tea manufacturers maintain their drinks' pH within 5-6.5 and 5-6 for coffee and tea, respectively. Soft drinks are usually within the pH range of 2.5-4.5. Beer stays within the 4-5 range while wine stays within 3-4. Automatic pH controllers also help beverage manufacturers during pH analysis. The controllers automatically add pH modifiers when the pH value goes beyond the acceptable range.
Automatic pH controllers for the chemical industry
The chemical industry uses many chemicals with highly variable pH values. This industry also performs intensive wastewater treatment. Therefore, it relies on automatic pH controllers to maintain pH levels and control neutralization during chemical processes. pH control is especially crucial in this industry, as it can determine the effectiveness of chemical reactions. For instance, some reactions require acidic medium, some alkaline, while others require neutral. Automatic pH controllers are commonly used in the chemical industry to help maintain the pH levels of effluent discharges before sending it out.
Automatic pH controllers for the pharmaceutical industry
The pharmaceutical industry also depends on pH values to optimize drug formulation processes and guarantee the safety of drugs. pH control is particularly important in drug formulation. For instance, the solubility, stability, and absorption of an active pharmaceutical ingredient (API) depend on the pH range. Automatic pH controllers are commonly used in the industry to help keep wastewater within the pH range of 2-12. Exposure to that pH range is dangerous, and pH controllers help neutralize it before discharge.
While there are many types and configurations of automatic pH controllers, they have some common features. This section will explore those features.
The primary role of an automatic pH controller is to maintain the setpoint pH value. Therefore, it automatically adds acid or alkaline solutions to neutralize the solution. Some advanced controllers also automatically calibrate themselves.
Automatic pH controllers usually come with this feature to improve accuracy. That is because temperature changes can alter the pH value of a solution. Most automatic pH controllers in the market compensate for temperature changes from 0 to 60°C.
Some advanced automatic pH controllers also correct the pH reading by the combined effect of conductivity. It does this using the Davies equation. According to the equation, the final corrected pH value depends on the initial pH reading and the conductivity coefficient. This is particularly useful for weak acids and alkalis, which can have misleadingly strong pH readings, altering the operator's perception of the solution's acidity or alkalinity.
Most automatic pH controllers have them. They inform users when the sensor needs maintenance, such as cleaning or replacing failure. Some of them also come with an evacuation feature that allows the controller to neutralize the solution automatically.
Some advanced digital pH controllers come with it. It allows users to analyze the solution's historical pH trends. This is helpful for industries that need to comply with environmental regulations.
When choosing automatic pH controllers, buyers consider the following factors:
One of the reasons users get automatic pH controllers is for them to maintain the setpoint pH value. If an automatic pH controller has high accuracy and precision, it will effectively maintain the setpoint pH value. So, what differences do accuracy and precision have? The former measures the closeness of pH readings to the actual pH value of the solution, while the latter refers to the pH value consistency during repeated measurements.
As seen in the previous sections, different types of automatic pH controllers have their advantages and disadvantages. Analog pH controllers, for instance, may not be as accurate as digital pH controllers. However, they are simpler to use, cheaper, and do not require power to operate.
Some automatic pH controllers come with extra features that can help improve their performance or increase their utility. For instance, temperature compensation can help ensure the controller's accuracy in environments with highly variable temperatures. Also, data logging can help monitor the system over time to determine optimal pH ranges for a solution.
Different industries require different pH ranges. So, the right automatic pH controllers for the chemical industry shouldn't be more acidic than 2 or less alkaline than 12. But the ocean water pH controllers can measure pH values ranging from 4 to 9. So, what buyers should do is look for controllers with measuring ranges suitable for their industry.
It's advisable to buy pH controllers with low resolution for high-resolution applications. For instance, controllers with 0.01 pH resolution will be useful during the formulation of highly sensitive drugs. On the other hand, controllers with 0.1 pH resolution are suitable for less sensitive applications, such as wastewater treatment.
Automatic pH controllers are tedious to maintain as they have to be kept clean. Additionally, the sensors used in those controllers should be replaced from time to time. Fortunately, some advanced digital pH controllers have self calibration features that automatically calibrate the sensor.
Yes, automatic pH controllers are used in wastewater treatment. They help maintain the pH of effluents within the safe range of 2-12 before discharging them out. Without the controllers, the pH value of wastewater would go beyond that range, making it unsafe to the environment.
It depends on several factors, such as the type of pH controller and the application's environment. That said, the average lifespan of pH sensors is usually between 6-12 months. However, the sensors in print and paper, and the chemical industry can last from 3-6 months due to the harsh conditions they undergo.
