What is the transmission?
Transmission is a device for measuring light when passing through medium, usually air or water. It is generally used as a means to determine the visibility in the atmosphere and the turbidity in the ocean. The device consists of a light source of known frequency and intensity, which can be a lamp, laser or light emitting diode (LED) and a detector located at a known distance. The detector converts the light that reaches it into an electrical voltage, which is proportional to the light intensity. The degree of transparency of interventing air or water can be determined by measuring the share of light from the source that is recorded in the detector.
The light attenuation of gases and particles in the atmosphere can be expressed as a coefficient of extinction of the atmosphere, which is the rate of light of the lost scattering and absorption of the distance. In order to obtain a value for this value, the light intensity measured by the detector must be compared with what could beExpect if no gases or particles were present between the source and the detector. The extinction coefficient will vary depending on the measured wavelength of the light, as different gases and particles absorb and distract different wavelengths of light to different ranges. For air visibility, a wavelength of 550 nanometers (Nm) is commonly used because it is in the middle of a visible light. When measuring water turning, the wavelength is 665 nm. In certain circumstances, separate measurements can be made for different wavelengths.
pollutants in the atmosphere can seriously reduce visibility. Light can be scattered by some substances such as sulphates and nitrates, and absorbed by others, such as smoke, soot and nitrogen oxide, responsible for brown haze, often observed around urban areas. For measuring air quality in terms of visibility, light light source and transmission detector can be placed 0.62-6.21 miles (1-10 km) apart to provide what is known as long CES measurementyou. Visibility can therefore be continuously monitored for the areas. In the US, the Agency for Protection of the Environment (EPA) was widely used to monitor visibility, as required by the Pure Air Act.
Transmission units are sometimes used on airports to check visibility. Some types of transmission are specially designed to be deployed in smoke piles at power plants to measure the opacity of the smoke cloud. In the ocean or in fresh water, the light can be prevented by suspended mud, disturbed sediment and microorganisms. The water can be measured by transmission with a light source and a detector located at the opposite ends of the tube about one meter long. This can be suspended in the water at the desired depth to fill the tube with water.