Dissolved Oxygen Online Analyzer Measurement Principle

(1) Membrane electrode method Membrane electrode method is a currently most commonly used method for continuous measurement of dissolved oxygen. The membrane electrode is also known as Clark oxygen electrode. This electrode utilizes the principle that the membrane is permeable to oxygen but cannot penetrate water and organic and inorganic solutes. The protective electrode does not come into close contact with such reducing substances, so that the sensitivity of the sensor is not affected. This semipermeable membrane is usually made of PTFE fibers, polyethylene, and other materials.

The membrane electrode method dissolved oxygen sensor consists of a gold electrode (cathode) and a silver electrode (anode) and a potassium chloride or potassium hydroxide electrolyte. Oxygen diffuses through the membrane into the electrolyte and the gold and silver electrodes form a measurement loop. When a polarization voltage of 0.6-0.8V is applied to the electrode of the dissolved oxygen analyzer, oxygen diffuses through the membrane, the cathode releases electrons, and the anode receives electrons, generating an electric current. The entire reaction process is:

Anode reaction: 4Ag 4Cl-→4AgCl 4e-

Cathodic reaction: O2 2H2O 4e-→4OH-

According to Faraday's law: When the electrode structure is fixed, at a certain temperature, the size of the diffusion current is directly proportional to the oxygen concentration of the sample, and the concentration of oxygen in the sample to be tested is known as the magnitude of the measured current.

(2) The non-membrane electrode sensor consists of a special silver alloy electrode (cathode) and iron electrode (anode). There is no cover film and a special electrolyte, and there is no polarization voltage between the two electrodes. It uses the solution to be tested as an electrolyte. The two poles form a primary battery and generate an electric current. The reaction formula is as follows:

Anode reaction: 2Fe→2Fe2 4e-

Cathodic reaction: O2 2H2O 4e-→4OH-

The magnitude of this current is proportional to the amount of oxygen molecules measured in the solution. The signal is sent to the transmitter together with the temperature signal measured by the thermal resistance of the sensor. The oxygen content in the water is calculated from the relationship curve between oxygen content and oxygen partial pressure and temperature stored in the sensor, and then converted into a standard signal. Output.

(3) Fluorine Dissolved Oxygen On-Line Analyzer Dissolved Oxygen Transmitter Features:

1. The system has password protection, output hold, output delay, analog output, relay output (optional) and real-time analog functions.

2. There are two calibration methods: 1 point calibration method (online) and air (offline) calibration method. In order to improve the accuracy of the sensor, the system will automatically detect important parameters such as temperature before accepting the calibration data.

3. The system has complete self-diagnosis information: When the measuring electrode is damaged, the sensor seal is damaged, and the temperature sensor is automatically alarmed when it is damaged.

4. The transmitter can customize the scale.

5. High reliability, good stability, simple operation and convenience.

6. Completely electrically isolated.

7. Dissolved oxygen is used to measure the content of oxygen in aqueous solution. Its measurement range is 0-40ppm. It adopts two-wire DC 24V power input and can output 4-20mA analog quantity. The length of power cable can reach 914 meters. Transmitter The distance to the sensor can reach 305 meters. Dissolved oxygen sensor features:

1. The sensor material has good mechanical strength and chemical resistance, and can adapt to a variety of harsh environments.

2. Three reaction electrodes are installed in an easy-to-replace reaction chamber, and the oxygen electrode is easy to change membranes.

a. Makes the sensor easy to regenerate, saving operating costs.

b. The output current of the three current sensors is proportional to the O2 pressure.

c. The cathode material is Jinyang and the pole material is silver. The reference electrode material is silver or silver bromide.

d. The reference electrode is used to stabilize the polarization potential. Ensure the accuracy of the measurement.

3. The built-in preamplifier improves sensor stability. The sensor-to-transmitter cable can be extended up to 305 meters.

4. When the measurement sensor's tightness is damaged, the built-in temperature sensor is damaged, and the reaction chamber membrane is damaged. The self-diagnosis system will reflect the alarm signal.