Moisture meter types and their working principle

Water analysis methods can generally be divided into two major categories, namely physical analysis and chemical analysis. Classical moisture analysis methods have been gradually replaced by various moisture analysis methods. Currently, there are mainly five types of moisture analyzers on the market. 1. Karl Fischer moisture analyzers:

The Karl Fischer method, which is called the Fischer method, is a volumetric separation method for measuring moisture content proposed by Karl Fischer in 1935. The Fischer method is the most specific and accurate method for determining water in various types of chemical methods. Although it is a classical method, it has been improved in recent years, improving accuracy and expanding the measurement range. It has been listed as a standard method for determination of moisture in many substances.

The Fischer-Tropsch method is an iodometric method. The basic principle is that when oxidizing sulfur dioxide with iodine, the need for quantitative water to participate in the reaction:

12 Ten S02 Ten 2H2O=2HI Ten H2SO4

The above reaction is reversible. In order to move the reaction in the positive direction and quantitatively, basic substances must be added. Experiments have shown that pyridine is the most suitable reagent, while pyridine also has the ability to combine with iodine and sulfur dioxide to reduce the vapor pressure of both. Therefore, the reagent must be added to methanol or another solvent containing a reactive OH group to convert the pyridine anhydride pyridine to a stable methyl bisulfate.

2. Infrared moisture meter:

Infrared heating mechanism: Absorption, reflection, and transmission occur when far-infrared radiation is radiated to an object. However, not all molecules can absorb far-infrared radiation, and only those polar molecules that show electricity can work. Water, organic substances, and high molecular substances have a strong ability to absorb far-infrared rays. When these substances absorb the far-infrared radiation energy and make its molecules, the frequency of natural vibrations and rotations of atoms coincide with the frequency of far-infrared radiation, molecules or atoms are likely to resonate or rotate, resulting in greatly increased movement and conversion into The heat energy raises the temperature inside, so that the substance is quickly softened or dried.

3. Dew point moisture meter:

The dew-point moisture analyzer is easy to operate, the instrument is not complicated, and the measured results are generally satisfactory. It is often used for the determination of trace moisture in permanent gas. However, this method interferes more. Some cold-changeable gases, especially at higher concentrations, interfere with condensation than water vapor.

4. Microwave moisture meter:

The microwave moisture analyzer uses a microwave field to dry the sample to accelerate the drying process. It has the characteristics of short measurement time, convenient operation, high accuracy and wide application range. It is suitable for grain, paper, wood, textile and chemical products, etc. The determination of moisture in powdered and viscous solid samples can also be applied to the determination of moisture in petroleum, kerosene and other liquid samples.

5. Coulomb moisture meter:

Coulomb moisture meters are often used to determine the moisture content of gases. This method is easy to operate, quick to respond, and especially suitable for the determination of trace moisture in gases. If you use ordinary chemical methods, it is very difficult. However, electrolytic methods are not suitable for the determination of alkaline substances or conjugated diolefins.