KST-V Cold Mirror Dew Point Meter

Main features of the product
1.Using SL micro cooler as the cooling sourceThis is the difference from a typical cold mirror dew point meter
2. Adopt inspection self-cleaning measurement method;
3. Adopting anti electromagnetic interference module design;


Introduction and Analysis of Characteristics
1. Cooling source - The cooling source is the core component of the cold mirror dew point meter, and the quality of the cooling source directly affects the main indicators such as the measurement range, measurement accuracy, and working environment of the dew point meter.
At present, the cold mirror dew point meters used in the power industry all use Peltier refrigeration chips as the cooling source,Peltier refrigeration chips use the thermoelectric principle to transfer heat to achieve refrigeration. During the refrigeration process, one side of the refrigeration chip continuously absorbs environmental heat and transfers it to the other side. When the cycle reaches a certain equilibrium with the ambient temperature, the temperature difference between the refrigeration surface and the ambient temperature accumulates, which is the temperature difference that the refrigeration chip can provide. The current high-quality Peltier cooled reactor can provide a temperature difference of 70 ℃, and when the ambient temperature reaches 40 ℃, its actual refrigeration limit is -30 ℃. In the power industry, the qualified standard for the moisture content of insulation gas in SF6 equipment is ≤ 150ppm, which is converted to a dew point temperature of ≤ -38.5 ℃. When a cold mirror dew point meter using Peltier as a cold source is used in an environment with a temperature higher than 31.5 ℃, it no longer meets its measurement requirements and cannot perform normal detection. In order to avoid this phenomenon, the industry has adopted the method of stacking multiple Peltier chips to form a refrigeration stack for multi-stage refrigeration. This method requires multiple stages of increasing Peltier chips to achieve. However, when multiple cooling chips are stacked, the phenomenon of heat transfer occurs, and the actual refrigeration effect is not significant. Additionally, large heat dissipation devices need to be equipped, resulting in a higher overall cost increase.
The KST-V cold mirror dew point meter adopts the company's independently developed SL micro cooler as the cooling source， The prototype of SL micro cooler is a deep low-temperature refrigeration machine, which adopts the principle of regenerative gas refrigeration. The lowest refrigeration temperature can reach below -200 ℃, and it is widely used in low-temperature laboratories, aerospace, military equipment, genetic engineering and other fields. The SL series micro cooler developed by the company for the civilian dew point meter industry controls the overall refrigeration power within the industry demand range, significantly reducing manufacturing costs and enabling this high-quality refrigeration device to be applied in ordinary industries. The Stirling cycle principle used in the SL micro cooler is currently the most efficient thermal cycle principle. Compared to the Peltier cycle principle, it has a higher cumulative heat/cold efficiency, which allows the SL micro cooler to easily achieve ideal refrigeration performance without complex cold energy stacking. At the same time, it completely avoids the negative effects caused by cold energy stacking. Therefore, the SL micro cooler has the advantages of wide refrigeration range, fast refrigeration speed, and strong environmental applicability, and can work normally at higher ambient temperatures.At present, international top dew point meter brands have also upgraded and developed cold mirror dew point meters using semi Stirling refrigeration technology, such as Michelle from the UK and MBW from Switzerland.

2. Measurement method - Cold mirror dew point is mainly measured based on the cold mirror principle, which is realized according to the characteristics of condensation on the mirror surface of gases with different moisture contents at different temperatures. Based on the cold mirror measurement principle, appropriate measurement methods can enable the equipment to accurately determine the true dew point temperature of the measured gas. At present, the measurement methods based on the principle of cold mirror measurement include visual inspection, balance method, and inspection method. The visual inspection method is the earliest generation of cold mirror dew point measurement method, which judges the dew point temperature by observing the condensation on the surface of the cold mirror with the naked eye. Due to poor operability, large accuracy errors, and poor repeatability, this measurement method has gradually been phased out. The balance method is the second generation dew point measurement method, which is popular at present. Through the combination of photoelectric detection technology and cold mirror principle, the gas dew point temperature is finally calculated by constantly balancing the frost layer thickness on the surface of the cold mirror. This measurement method has good measurement accuracy when the equipment and gas pipeline environment are relatively dry and clean, and it is fully automatic measurement, easy to operate, and convenient to use. Due to the characteristics of its measurement method, the balance method significantly reduces its detection accuracy in situations where gas impurities are high, gas pipelines are not clean enough, environmental conditions are poor, and equipment is poorly stored and internally contaminated. The main reason for this phenomenon is that during the measurement process, the surface of the cold mirror continuously condenses the moisture in the gas, and the pollutants in the gas will be condensed together on the mirror surface. When there are too many pollutants, the photoelectric detection module will make a misjudgment, leading to the phenomenon of early or delayed determination of dew point temperature. The measured value will have a significant error compared to the actual dew point value.

3. Patrol measurement method is a new generation of cold mirror dew point measurement method developed to make up for several defects of the balance measurement method. It is the same as the balance method in principle, and is combined with the photoelectric detection technology through the cold mirror principle. The difference is that the patrol measurement method abandons the balance method to calculate the dew point through the frost layer thickness on the surface of the cold mirror, and adopts a more scientific, direct and reliable direct measurement form. When the frost point appears on the surface of the cold mirror, the photoelectric system records its data and restores the accurate dew point through scientific algorithms. Due to the lack of a continuous process of balancing the frost layer, under the same measurement conditions, the measurement speed of the inspection measurement method will be superior to that of the balance measurement method. Another major feature of the patrol measurement method is its self-cleaning function. At the moment when the frost spots appear on the surface of the cold mirror, in addition to the dew data recorded by the photoelectric system, the surface of the cold mirror has started to heat up until the frost spots on the surface of the cold mirror melt. With the airflow, the moisture and pollutants on the surface of the cold mirror will be purged away together to prepare for the next measurement. This measurement method greatly reduces the probability of contamination of the cold mirror surface, improves the measurement accuracy and environmental adaptability of the equipment, and extends the maintenance cycle of the equipment.

4.3. Electromagnetic interference - In the power industry, it is a common phenomenon for instruments and equipment to be affected by electromagnetic interference. Mild electromagnetic interference can reduce equipment performance, while severe interference may cause damage to the equipment. In response to the usage environment of power users, the dew point meter adopts an anti electromagnetic interference module design internally, with an independent power supply module built in to completely avoid power grid interference. The core components of the product are all protected by electromagnetic interference resistant material shielding layers or coatings, and the power conduction and signal transmission are also reasonably designed to resist electromagnetic interference. The dew point measurement software independently developed by the company adopts self correction and poor comparison measures, greatly reducing the phenomenon of equipment performance damage caused by electromagnetic interference.