Application of infrared and microwave moisture meters in production line

First, the principle of two moisture meter 1. Infrared moisture meter Infrared moisture meter is the use of infrared spectroscopy to analyze the moisture content of the instrument. Infrared light is an electromagnetic wave, all kinds of electromagnetic waves have a certain energy, different wavelengths have different energy. Various substances have the ability to absorb the energy of electromagnetic waves, but this absorption is selective. Different molecules have different wavelengths of absorbed electromagnetic waves. A molecule can only absorb electromagnetic waves of one or several wavelengths. However, the energy of electromagnetic waves at other wavelengths does not have absorption capability.

Figure 1 shows a schematic diagram of an infrared instrument. The infrared light source 1 passes through a rotating filter 2 equipped with two filters of different wavelengths, one filter passes infrared light having a wavelength of 1.94 micrometers, which is the absorption band of water; the other filter passes the wavelength of 1.8 micrometers Infrared rays cannot be absorbed by water. The material to be measured 6 is exposed to an infrared beam, reflected, collected by a lead sulfide detector 3 and converted into an electrical signal. After being amplified, the signal ratio of the two wavelengths is displayed by the indicator meter 11, and the moisture content can be measured.

2. Microwave Moisture Meter The working principle of the microwave moisture meter is high-accuracy resonance measurement. The microwave resonant frequency it uses is 2000~3000 MHz. When the microwaves pass through a substance containing moisture in the transmission, part of the electromagnetic energy is absorbed by the water molecules and the microwave intensity is attenuated. On the other hand, the conversion of the positive and negative oxygen ions and hydrogen ions in the water molecules in the electric field affects the resonant frequency.

Fig. 2 is a block diagram of a microwave moisture analyzer, which is mainly composed of a microwave oscillator 3 and a microwave attenuator 5, and a microwave signal is transmitted from a waveguide through a sample 4, which is accepted by the microwave attenuator, and is indicated by an indicator after the amplifier 6 and the detector 7 8 shows, you can measure the moisture content.

Second, the comparison of the two moisture meters in the application of infrared moisture meter for online non-contact measurement, so there is a strong adaptability of the production environment and conditions, such as high temperature, high humidity, corrosive materials, and other measurements Large range, no special requirements on the temperature of the material. However, due to the limited penetration of infrared light, the infrared moisture meter can only detect the moisture on the surface of the material, and the measurement result is susceptible to the quality, color, and structure of the material being measured. At the same time, there are strict regulations on the installation location. Because the measuring beam of the instrument has a focusing distance, installing too high or too low will affect the energy focusing of the infrared light, which will result in measurement errors. In addition, the probe's mirror surface is susceptible to contamination, resulting in a decrease in sensitivity and measurement accuracy; in addition, the influence of external light on its effects must be considered.

The microwave moisture meter is contact-type measurement, so it has higher requirements on the environment of the measured materials, such as environmental temperature, humidity, corrosivity of the materials, etc. The surface characteristics of the products have little effect on their measurement results. In order to have relatively stable measurement results and high measurement accuracy, there is also a high requirement for the installation of the probe. Because the probe contact surface is easily contaminated, it easily leads to a decrease in sensitivity and measurement accuracy.

By comparison, it can be seen that the principle and practical application of the two moisture meters are different. Therefore, the smoke machine companies must combine their own technical level, application environment, and measurement objects when considering the equipment transformation and selection. Instrument performance to achieve the best, in order to improve product market competitiveness to provide equipment protection.