Dissolved oxygen electrodeIt can be used to measure the dissolved oxygen content in the aqueous solution of the tested sample on site or in the laboratory. The dissolved oxygen electrode uses a thin film to separate the platinum cathode, silver anode, and electrolyte from the outside world. Generally, the cathode is almost in direct contact with this film. Oxygen diffuses through the membrane at a ratio proportional to its partial pressure, and the higher the partial pressure of oxygen, the more oxygen passes through the membrane. When dissolved oxygen continuously penetrates through the membrane and infiltrates the chamber, it is reduced on the cathode to generate an electric current, which is displayed on the instrument. Since this current is directly proportional to the dissolved oxygen concentration, the calibration instrument only needs to convert the measured current into concentration units.
Dissolved oxygen electrodeThe construction of
The dissolved oxygen electrode is an electrochemical cell composed of silver and gold electrodes embedded in insulating materials. The silver electrode is used as the anode and is generally made into a circular ring shape. As a reference electrode, the area of the silver electrode should be as large as possible to reduce the current density on the electrode surface and minimize the polarization phenomenon of the anode, so that its electrode potential is not affected by external voltage. The gold electrode serves as the cathode and is usually made into a circular dot shape, located in the center of the silver electrode. The electrolytic reaction occurs on the gold electrode.
Dissolved oxygen electrodePolarization of
When used or continuously powered off for 5-10 minutes or more, polarization occurs after connecting to the instrument and powering it on. To achieve equilibrium in the chemical system of the electrode, reduce the zero oxygen current, and stabilize the electrode. At the beginning, the current of the dissolved oxygen electrode is relatively high and decreases exponentially. After 6 hours, it reaches a stable state, during which the displayed data will gradually decrease until it stabilizes. Calibration can only be carried out later.
The polarization process takes 6 hours. First, connect the electrode correctly to the secondary meter and turn on the instrument power. If the power off time is not long, the polarization time will be shorter and more stable.