Optical dome - the basic component of a total solar radiation meter
A total solar radiation meter is an instrument used to measure the total solar radiation, which is based on the principle of extrapolating the total solar radiation by measuring the energy loss of sunlight as it passes through the atmosphere.
What is a pyranometer?
A pyranometer is an instrument used to measure the total solar radiation, which is based on the principle of extrapolating the total solar radiation by measuring the energy loss of sunlight after it passes through the atmosphere. Total solar radiation is an important factor in the energy balance on the Earth's surface and has a significant impact on climate, ecosystems, and human life. Total solar radiation is the sum of the energy released to the Earth by the Sun in various forms, including visible, ultraviolet, and infrared radiation from the Sun.
The construction of a pyranometer usually consists of a photothermal system, an energy collector, and an energy measurement system. The function of the photothermal system is to focus sunlight onto the energy collector, which converts the light energy into electrical energy, and finally, the total solar radiation is measured by the energy measurement system.
Pyranometers usually contain the following information:
1. Date and time: the date and time of the radiation measurement are recorded to allow comparison of radiation levels over time.
2. total radiation directed to the Earth: the total radiant energy directed from the Sun to the Earth's surface.
3. solar radiation component: the division of the sun's radiant energy into wavelength ranges, usually visible, ultraviolet, and infrared.
4. Radiation intensity: refers to the radiant energy received per unit area per unit time, usually expressed in watts per square meter (W/m2).
5. Radiation change chart: record the radiation intensity of different periods, and through the chart to show its trend.
When measuring a pyranometer, several factors need to be taken into account. First, geographic location and altitude have a significant impact on the results of total solar radiation measurements, so measurements need to be taken at different geographic locations and altitudes to obtain accurate data. Secondly, the composition of gases in the atmosphere and substances such as aerosols also affect the transmission rate of sunlight, so measurements need to be made under different meteorological conditions to obtain accurate data.
Measurements of pyranometers can be used for research and applications in a variety of fields. For example, in the field of climatology, measurements of a pyranometer can be used to study changes in the Earth's climate and the factors that influence it; in the field of ecology, measurements of a pyranometer can be used to study the flow of energy and the cycling of materials in ecosystems; and in the field of agriculture, measurements of pyranometer can be used to study the factors influencing the growth and yield of crops.
Composition of the pyranometer
1. The pyranometer consists of a double quartz glass cover, a sensing element, a light shield, a meter body, and a desiccant. The inductive element is the core part of the meter, which is composed of a fast-responding wire-wound electroplated thermopile. The inductive surface is coated with 3M non-glossy black paint, the inductive surface is a hot junction, when there is sunlight irradiation the temperature rises, and it and the other side of the cold junction form a temperature difference electromotive force, which is proportional to the intensity of solar radiation.
2. The double-layer Laboratory Centrifuges of the pyranometer is used to reduce the impact of air convection on the pyranometer. The inner cover is designed to cut off the infrared radiation from the outer cover itself.
3. Pyranometer output radiation amount (W/m) = measured output voltage signal value (μV) ÷ sensitivity coefficient (μV/W·m). Each sensor gives a calibrated sensitivity coefficient.
Usage and Maintenance
For pyranometer observations at meteorological stations, the metal cover should be opened before sunrise, the radiation meter will start sensing, and the recorder will automatically display the instantaneous and cumulative total radiation. The cover is put on after observation is stopped at sunset. If there is no precipitation or other phenomena that may damage the instrument at night, the total radiation meter may not be covered.
Whether the instrument is horizontal, the induction surface and the glass cover are intact. Whether the instrument is clean, the glass cover, such as dust, frost, fog, snow, and raindrops, should be lens brush or buckskin in time to clean, pay attention to not scratch or wear the glass. The glass cover should not be watered, and there should be no water vapor condensation inside the cover. Check whether the silica gel in the drier becomes damp (it can no longer be used after it turns from blue to red or white), otherwise, it should be replaced in time. Damp silicone can be baked in the oven to dry back to blue before use. Total radiation table waterproof performance is good, general short time or small precipitation can not cover. However, in heavy rainfall (snow, hail, etc.) or a longer period of rain and snow, to protect the instrument, the observer should based on the specific circumstances of the timely addition of the cover, that is after the rain stops to open the cover.
Fused Silica Domes
Optical domes are mainly used to protect precision instruments, and cameras in harsh environments. Common fused silica glass is divided into ultraviolet silica glass and infrared silica glass.
UV fused silica in 190nm-2650nm has relatively good transmittance, but at about 2200nm, 2650nm will appear absorption phenomenon, which is due to the high content of hydroxyl in the fused quartz absorption. Infrared quartz glass has good optical transmittance at 280nm-3800nm.
If the protected object is used in the ultraviolet band, UV quartz glass is a better choice. If the application is used in the infrared band, infrared fused silica will be more suitable.
Meanwhile, compared with common optical glass H-K9L, N-BK7, etc., the mechanical strength and chemical properties of fused silica are better, but the price of its blank is much higher than that of common optical glass. Quartz glass is also a better choice if common optical glass cannot meet the usage requirements.
The fused silica is a special industrial technical glass made of silica, which is a very good basic material. The heat resistance of quartz glass is very high, with a frequent use temperature of 1100℃~ 1200℃ and a short-term use temperature of up to 1400℃. Quartz glass is mainly used in laboratory equipment and refining equipment for special high-purity products.
Fused silica has a series of excellent physical and chemical properties, such as:
1. High-temperature resistance: the softening point temperature of quartz glass is about 1730℃, it can be used for a long time under 1100℃, and the maximum temperature for a short time can reach 1450℃.
2. Corrosion resistance: in addition to hydrofluoric acid, quartz glass has almost no chemical reaction with other acids, its acid resistance is 30 times that of ceramics, 150 times that of stainless steel, especially at high temperatures in the chemical stability of any other engineering materials are incomparable.
3. Good thermal stability: the thermal expansion coefficient of the adapted glass is extremely small, and can withstand drastic temperature changes, the quartz glass will be heated to about 1100 ℃, into the room temperature water will not blow up.
RZ Optics Co., Ltd. is a manufacturer of optical components, and main products including optical lenses, domes, windows, etc. Our products are widely used in aerospace, medical, camera, infrared technology, etc. Including the total radiation meter mentioned herein, consisting of a fused silica dome.
Please contact us free time if you are interested in our product.