Benefits of adopting optical dissolved oxygen sensor

Writer： admin Time：2024-03-11 16:57:38 Browse：502℃

What is Dissolved Oxygen

Dissolved Oxygen, abbreviated "DO", refers to the amount of oxygen dissolved in water, which is expressed in milligrams of oxygen per liter of water, and exists in a molecular state in water.

Electrode Classification for Dissolved Oxygen Sensor

Currently, there are two types of membrane electrodes commonly used for dissolved oxygen sensors: fluorescence and polarography.

Fluorescence method dissolved oxygen sensor is based on the principle of fluorescence burst, blue light irradiation to the fluorescent material to make the fluorescent material excitation and emit red light, because the oxygen molecules can take away the energy, so the time and intensity of the excitation of the red light and the concentration of oxygen molecules is 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.

Principle of Polarographic Dissolved Oxygen Measurement: The polarographic sensor consists of a silver anode and a gold cathode in a circular shape at the bottom, and a thin semi-permeable membrane, which is unfolded over the sensor, isolates the electrodes from the outside world while allowing gas to enter. During operation the bottom of the sensor is filled with a small amount of surfactant electrolyte to enhance wetting.

Advantages of Fluorescence Dissolved Oxygen

Compared with the fluorescence method, the polarographic method is easy for sludge to paste the membrane, and the sludge has little effect on the fluorescence method DO measurement. Fluorescence method DO measurement is indeed faster than polarographic measurement response, long use time and other advantages, but the fluorescence method DO meter price is more expensive.

Traditional membrane DO meters require frequent replacement and cleaning of the probe due to the membrane and electrolyte, and the data are prone to drift. Fluorescence dissolved oxygen measurement does not require frequent cleaning of the probe, the data is stable, the measurement response time is fast, the effect is to save energy as well as to ensure the degradation effect.

The advantages of the combined comparative fluorescence method are as follows:

1、No need to calibrate
Because it is a fluorescence method design. So there is no need for calibration, which greatly reduces the maintenance workload in the use of the instrument.

2、Measurement results are stable
The fluorescence method is used to measure dissolved oxygen because it does not consume any substances during the measurement process, nor does it consume dissolved oxygen in the water, so the measurement results of this measurement method are more stable.

3、Reduce cleaning frequency
The traditional membrane method needs to be cleaned frequently, otherwise it will seriously affect the oxygen transmission, thus affecting the measurement. Fluorescence method does not have high cleaning requirements for the probe, and the fluorescence cap can be wiped regularly.

4、Low maintenance
Because the fluorescence method does not require calibration, frequent calibration, replacement of the membrane (RO membrane), frequent cleaning, so its installation and use of the maintenance is very low.

5、No interference
Changes in pH, chemicals contained in sewage, H2S, heavy metals, etc. will not interfere with the measurement, in addition to its own oxidizing properties, which may be measured by the ordinary dissolved oxygen electrode as oxygen; carbon dioxide in the electrolyte will affect the measurement, mainly by changing the conductivity of the electrolyte, while LDO does not have an electrolyte, and therefore will not be affected by the carbon dioxide.

6、Without polarization time, fast response time
Since no electrode is used, there is no polarization problem.
LDO can respond at the same time as it comes into contact with water, and its time is very short.