Principle of online pH meter

When installing an online pH meter, the electrodes need to be measured in a sealed environment to obtain accurate values, otherwise the contact between the medium and air can affect its measurement results.

The online pH meter has the characteristics of Chinese (English) display, single operation of Chinese (English) dishes, full intelligence, multifunctionality, high measurement performance, and strong environmental adaptability. This table is a highly intelligent online continuous monitoring instrument, consisting of two parts: sensors and secondary meters. Can be equipped with three composite or two composite electrodes to meet various usage scenarios. It can be widely used for continuous monitoring of pH values in solutions such as thermal power, chemical fertilizers, metallurgy, environmental protection, pharmaceuticals, biochemistry, food, and tap water.

Brief measurement principle:

The instrument (electronic unit) consists of signal measurement, operation, display, network communication, and panel instructions. The impedance transformation of pH and temperature transmission changes the pH to a low impedance signal of 459.16mV/pH (25 ℃); Convert NTC into a voltage signal. The pH electrode of the instrument and sensor is matched to monitor the pH value of the solution. The sensor is a battery composed of a pH glass electrode and a calomel (or Ag/AgCl) reference electrode, which generates a potential difference related to the pH value of the solution based on the Nernst equation: Ex=Eo+SPH.

The potential difference is amplified by a preamplifier stage with high input impedance, and the thermistor sends out a signal corresponding to the temperature value. After amplification, the two signals are converted from A/D and processed by an I/O interface chip. After being processed by a single-chip microprocessor, they are prominently displayed on the display screen.

Principle of electrode structure:

(1) Internal reference electrode: It is a silver/silver chloride electrode, mainly used to extract electrode potential, requiring stable potential and small temperature coefficient.

(2) Internal reference solution: an internal reference solution with a zero potential of 7pH.

The pH value at which the glass electrode and reference electrode form the zero potential of the battery mainly depends on the pH value and chloride ion concentration of the internal reference solution.

Electrode slope: Theoretically, the slope of a glass electrode is 59.16mv at 25 ℃, which means that for every pH change in the solution, the glass electrode produces a potential change of 59.16mv. However, in reality, all glass electrodes cannot reach the theoretical value 100%, and the electrode slope is generally 98% or more of the theoretical value (percentage slope). In addition, there is a certain variation in the mv difference corresponding to each unit of pH value at different temperatures

When installing an online pH meter, the electrodes need to be measured in a sealed environment to obtain accurate values, otherwise the contact between the medium and air can affect its measurement results. In sealed environment measurement, a flow-through installation is required, and the matching installation of the flow-through pool is generally a bottom inlet and top outlet method. Ensure that the instrument electrodes are always isolated from the outside during the measurement process to prevent the medium from coming into contact with the outside air, which may affect the accuracy of the measurement data.

Precautions for using online pH meter:

Please follow the operating procedures and precautions in this manual when using.

If any abnormal or damaged instrument is found during use, please contact the dealer and do not repair it yourself.

To make the measurement more accurate, the instrument must be calibrated frequently in conjunction with electrodes.

Please power on and preheat the instrument for thirty minutes before performing calibration work.