What factors will affect the biological detection results of dissolved oxygen meters?
The dissolved oxygen analyzer is a necessary testing machine and equipment for QS and HACCP validation in food companies and domestic water plants. What are the factors that affect the measurement results of a dissolved oxygen analyzer, as there may be inaccurate measurements during the entire application process?
Firstly, due to temperature changes, the diffusion coefficient of the membrane and the solubility of oxygen will both vary greatly, immediately affecting the output of dissolved oxygen level current. Thermistors are often used to eliminate the influence of temperature. As the temperature increases, the diffusion coefficient increases and the solubility decreases.
Secondly, the influence of atmospheric pressure, according to Henry's basic law, is proportional to the partial pressure circuit between the solubility of the vapor. Oxygen partial pressure is related to the altitude of the region, with a difference of up to 20% between high-altitude and plain areas. Compensation must be based on local atmospheric pressure before application. Some instrument panels are equipped with pressure gauges inside, which can automatically perform calibration on time; Some instrument panels are not equipped with pressure gauges, and calibration should be based on the statistical data presented by the local meteorological station. If the statistical data is incorrect, it will cause significant data errors.
There is also the effect of salt content on dissolved oxygen. Under the condition that the temperature does not change, for every 100mg/L increase in salt water content, dissolved oxygen decreases by about 1%. If the salinity of the aqueous solution used for calibration on the dashboard is low, and the salinity of the accurately measured aqueous solution is high, it will also cause deviation. In specific applications, it is necessary to analyze the salt content of accurately measured substances for accurate measurement.
Finally, there is the influence of flow velocity. The flow rate of the sample is slower for oxygen to diffuse through the membrane than through the sample, and it is necessary to ensure complete contact between the electrode membrane and the solution. For the flow detection method, oxygen in the solution will diffuse into the flow cell, causing a loss of oxygen in the solution near the membrane, resulting in diffusion interference and affecting the measurement. For accurate measurement, the flow rate of the solution flowing through the membrane should be increased to compensate for the diffusion loss of oxygen. The minimum flow rate of the sample is 0.3m/s.
