Core operating principle of Zhongruixiang online microgram level dissolved oxygen detector

Based on electrochemical or optical sensing technology, it is used for continuous monitoring of extremely low concentrations (microgram level, i.eppbDissolved oxygen levels. The following explanation will be based on common technical details.

Measuring principle

This type of instrument usually uses‌Diaphragm electrode method‌(Electrochemical principles) or‌Principle of optical fluorescence quenching‌.

‌Principles of electrochemistry‌Represented by polarographic or electrochemical electrodes. The electrode is made of platinum cathode and silver/Composed of silver chloride or lead anode and electrolyte, covered with an oxygen semi permeable membrane on the outside. When the electrode is immersed in a water sample, dissolved oxygen permeates the membrane and undergoes a reduction reaction at the cathode (such asO₂+ 2H₂O + 4e⁻ →4OH⁻）Generate a diffusion current that is proportional to the oxygen concentration. By measuring the current value and converting it through an instrument, the dissolved oxygen concentration can be obtained. Polarographic electrodes require an external polarization voltage (usually0.6–0.8V）The original battery type electrode spontaneously generates voltage without preheating.

‌Principles of Optics‌Based on fluorescence quenching effect. The fluorescent substance at the front end of the sensor emits fluorescence after being excited by light. Dissolved oxygen will quench the fluorescence intensity, and the degree of quenching is related to the oxygen concentration. By detecting changes in fluorescence decay time or intensity, the dissolved oxygen content can be calculated. Optical methods avoid membrane diffusion interference and are more suitable for detecting trace amounts of oxygen.

Key operational points

‌Signal Conversion and Compensation‌：

The current signal generated by electrochemical sensors needs to be amplified and linearized, and converted into concentration units (such as μ m)g/Lorppb）.

Instruments are usually integrated‌Automatic temperature compensation‌(Through)PT100Thermistor)‌Salinity correction‌and‌Atmospheric pressure compensation‌Function to eliminate the influence of environmental factors on measurement. For example, every change in temperature1℃The oxygen solubility coefficient changes approximately2%Real time calibration is required.

‌Calibration and maintenance‌：

Calibration adopts a two-point calibration method: the zero point is calibrated with nitrogen saturated water or sodium sulfite solution, and the range is calibrated with a known oxygen concentration solution (such as air saturated water).

For microgram level detection, it is necessary to regularly clean the electrode surface, replace the electrolyte (to avoid bubbles), and use a dedicated kit to calibrate in a constant temperature and pressure environment to ensure accuracy.

‌Data processing and output‌：

The instrument has a built-in microprocessor that can automatically store data (such as...)800Group record), conduct electrode performance testing, and passRS232Bluetooth orWi-FiTransfer data. The display interface usually synchronously displays dissolved oxygen value, temperature, and electrode status.

Precautions

‌Sample flow rate‌To ensure measurement accuracy, it is necessary to ensure that the flow rate of the water sample through the electrode membrane is not less than0.3m/sTo avoid diffusion interference.

‌Applicable scenarios‌This type of instrument is widely used in applications that require high sensitivity, such as sewage treatment, drinking water monitoring, and industrial process control. Optical sensors have significant advantages in detecting trace amounts of oxygen due to their anaerobic consumption characteristics.

Through the above principles and operational design, the online microgram level dissolved oxygen detector can achieve high-precision and continuous real-time monitoring.