Monitoring method and principle of dissolved oxygen analyzer for water quality
Dissolved oxygen detection is a very important indicator for water quality testing. The application of dissolved oxygen meters includes water environment monitoring, fisheries, wastewater discharge control, and laboratory detection of BOD. The large screen display screen of the water quality dissolved oxygen detector can display the detection results in mg/l units or air saturation percentage, and also display the temperature. Instruments controlled by microprocessors provide advanced dissolved oxygen detection technology.
The measurement methods and principles used in water quality dissolved oxygen meters are as follows:
1. Membrane method (also known as polarography or constant pressure method)
The measurement principle of dissolved oxygen analyzer is that the solubility of oxygen in water depends on temperature, pressure, and the salts dissolved in water. The sensing part of the dissolved oxygen analyzer is composed of a gold electrode (cathode) and a silver electrode (anode), as well as an electrolyte of methyl chloride or potassium hydroxide. Oxygen diffuses through the membrane and enters the electrolyte, forming a measurement circuit with the gold electrode and silver electrode. When a polarization voltage of 0, 6-0, or 8V is applied to the electrode of the dissolved oxygen analyzer, oxygen diffuses through the membrane, the cathode releases electrons, and the anode receives electrons, generating a current. The entire reaction process is as follows: anode Ag+Cl → AgCl+2e - cathode O2+2H2O+4e → 4OH - According to Faraday's law, the current flowing through the electrode of the dissolved oxygen analyzer is proportional to the oxygen partial pressure, and there is a linear relationship between the current and oxygen concentration under constant temperature.
2. Fluorescence method
The fluorescence probe is equipped with a built-in light source, which emits blue light to illuminate the fluorescence layer. The fluorescent substance is excited and emits red light. Due to the quenching effect of oxygen molecules, the time and intensity of the excited red light are inversely proportional to the concentration of oxygen molecules. By measuring the phase difference between the excited red light and the reference light, and comparing it with the internal calibration value, the concentration of oxygen molecules can be calculated. No oxygen consumption during measurement, stable data, reliable performance, and no interference.
How to measure the dissolved oxygen in water
The measurement of dissolved oxygen in water can be carried out using the Yushan fluorescence dissolved oxygen sensor, which adopts the new generation fluorescence lifetime technology and is independently developed by Yushan as a high-performance fluorescent material. It does not consume oxygen, has no flow rate restrictions, does not require electrolyte, is free from maintenance and calibration, is not affected by hydrogen sulfide interference, and has excellent stability. Built in temperature sensor, automatic temperature compensation. RS485 output, can be networked without the need for a controller. It can be easily integrated into water quality monitoring systems to meet customer needs.
