Introduction
Principle & Structure
pH value is used to express the value of hydrogen ion activity in solution, its definition is: pH=-Iga H+
where a H+ refers to the activity of hydrogen ions. In fact, when pH equals 0, the concentration of hydrogen ions in a solution is pH
It is 1×1014 times when it is 14. At the same time, this also means that the concentration of hydroxide ions in the solution when the pH value is equal to 14 is 1 × 1014 times that when the pH value is 0. When the concentration of hydrogen ions and hydroxide ions are equal (that is, the solution is neutral), the pH value is equal to 7. A pH value between 0 and 7 is called acidic, and a pH value between 7 and 14 is called alkaline. Keep in mind that a change in pH of 1 (eg from 6 to 7) means a 10-fold change in hydrogen ion concentration.
The pH meter commonly used in pH value determination consists of a glass electrode and a reference electrode to form a complete electrode system
The two different solutions of the glass electrode are separated by a glass film that is sensitive to changes in pH value. There is a constant potential on the glass membrane of the inner solution. Similarly, there is also a potential on the glass membrane of the outer solution that changes linearly with the pH value when the temperature is constant. The potential change caused by the change of each unit pH value is called the potential gradient.
The pH sensor is a composite electrode composed of a glass indicator electrode and a reference electrode. The measurement of pH is based on the potential difference measured in the solution of the working battery composed of the measuring electrode and the reference electrode, and realizes the online monitoring of pH by using the linear relationship between the pH value of the solution to be measured and the potential of the working battery.
The determination of pH value by temperature is mainly related to the following three aspects: the reference electrode used, the pH value of the known solution in the glass electrode, and the pH value of the solution to be measured. At a certain pH value, the temperature has no effect on the potential of the electrode system, and this pH value is called the equipotential point. In addition, at a certain pH level, the potential value of the system is 0V, which is called the zero potential point.
Whether it is the equipotential point or the zero-potential point, it is different according to the selected electrode. When the isoelectric point and zero-potential point of the electrode system in the product are both pH=7, the temperature has the least influence on most of them at this pH value.
Features
● Simple cleaning and activation, and fast balancing;
● Automatic temperature compensation function;
● Sensor connection status display (online/offline);
● Built-in self-diagnosis function to ensure accurate data;
● Built-in self-diagnosis function to ensure accurate data;
● The distance between the sensor and the transmitter can reach over 100 meters;
● Standard digital signal output, special transmitter-free industrial and mining can realize integration and networking with other equipment;
● Modular installation of sensors to achieve plug and play;
● English and Chinese display can be switched, and it is more convenient to use Chinese.
application
On-line monitoring of pH in the process flow of sewage treatment plant inlet and outlet, sedimentation tank, biochemical reaction tank, etc.;
pH monitoring in municipal water supply industry, surface water, aquaculture and other industries;
PH on-line monitoring of water and wastewater treatment processes in various industrial production processes.