Dissolved oxygen meters have become a core tool in the field of water quality monitoring due to their diverse technical routes and advantages. Users can choose the appropriate model according to their specific needs to achieve accurate dissolved oxygen analysis.

1. Polarography: This is one of the traditional mainstream techniques. When oxygen in the sample diffuses through a specially designed semi permeable membrane to the surface of the sensing electrode, a reduction reaction occurs, and the resulting diffusion current intensity is proportional to the concentration of dissolved oxygen in water. By detecting the current signal and converting it through circuit processing, the specific value of dissolved oxygen can be obtained. This method relies on the electrolysis process and typically requires regular calibration to maintain accuracy.

2. Fluorescence method: using optical sensors instead of electrochemical components. Specifically, a light source excites a fluorescent substance to emit light of a specific wavelength, while oxygen molecules quench this fluorescence effect. The instrument calculates dissolved oxygen content by monitoring the degree of fluorescence attenuation. Compared to polarography, fluorescence method does not require electrolyte consumption and is not affected by flow rate, making it more stable.

Measurement steps of dissolved oxygen measuring instrument:

1. Sampling and fixation: At the sampling site, insert a pipette into the liquid level of a 250 mL dissolved oxygen bottle, add 1 mL of MnCl2 solution and 1 mL of alkaline potassium iodide in sequence, cover the bottle stopper, invert and mix several times, and let it stand to complete the fixation of dissolved oxygen. The purpose of this step is to convert dissolved oxygen in water into a detectable form through chemical reactions.

2. Temperature control: Due to the influence of temperature on dissolved oxygen concentration, it is necessary to maintain the sample at a constant temperature for measurement. This helps to improve the accuracy and comparability of measurements.

3. Electrode insertion: Pour the processed sample into a dedicated measuring chamber or measuring bottle, and then slowly and steadily insert the dissolved oxygen electrode into the sample, ensuring that the electrode is submerged and does not touch the container wall or other obstacles.

4. Stirring solution: During the measurement process, the solution should be stirred appropriately. This is because the consumption of oxygen by the electrode will cause an instantaneous decrease in the concentration of oxygen on the surface of the probe. Stirring can promote the diffusion of oxygen to the electrode surface, thereby obtaining more stable readings.

5. Read data: After the instrument displays a stable value, record the current dissolved oxygen concentration value.