What environmental factors affect the temperature measurement accuracy of thermal imaging sights?

(1) Atmospheric environmental factors

Atmospheric temperature and humidity: Changes in atmospheric temperature will affect the heat exchange process between the target object and the thermal imaging sight. At different atmospheric temperatures, the propagation and absorption characteristics of thermal radiation are different. For example, in a high temperature environment, the thermal signal received by the thermal imaging sight may be interfered by the surrounding hot air, resulting in a decrease in temperature measurement accuracy. Humidity will also affect the temperature measurement accuracy. In a high humidity environment, water vapor will absorb and scatter infrared rays, especially in certain infrared bands. This absorption and scattering will weaken the target heat signal received by the thermal imaging sight, thereby affecting the temperature measurement accuracy.

Atmospheric pressure and altitude: Atmospheric pressure is related to altitude. As the altitude increases, the atmospheric pressure decreases. This change will affect the density and composition of the air, thereby changing the transmission characteristics of thermal radiation in the atmosphere. At high altitudes, the air is thin, and the scattering and absorption process of thermal radiation is different from that at low altitudes. When thermal imaging scopes work at different altitudes, it is necessary to consider the impact of these factors on the temperature measurement accuracy, because the thermal signal of the target object may change during transmission due to changes in atmospheric pressure.

Meteorological conditions: Weather phenomena such as rain, snow, and fog will have a significant impact on the temperature measurement accuracy of thermal imaging scopes. Raindrops, snowflakes, and fog droplets absorb, reflect, and scatter infrared rays, causing the thermal signal of the target object to attenuate or distort during transmission. For example, in heavy rain, the thermal imaging scope may receive more thermal signals from raindrops or blurred signals after being interfered by raindrops, making it difficult to accurately measure the true temperature of the target object.

(2) Target background environmental factors

Background temperature and radiation characteristics: The background temperature and radiation characteristics around the target object will interfere with the thermal imaging scope's measurement of the target temperature. If the background temperature is close to the target temperature, or the background has strong thermal radiation, such as hot ground or heating buildings under direct sunlight, the thermal imaging scope may find it difficult to accurately distinguish the thermal signals of the target and background, thereby affecting the temperature measurement accuracy. For example, in a desert environment, the temperature of the sand is very high under sunlight. When the temperature of the target object (such as a small animal) is not much different from that of the sand, it becomes difficult to accurately measure the target temperature.

Heat exchange process between the target and the background: There are heat exchange processes such as heat conduction, convection and radiation between the target object and the background. These processes will change the surface temperature of the target object, thereby affecting the temperature measurement accuracy of the thermal imaging scope. For example, when the target object (such as metal equipment) is placed on the low-temperature ground, heat conduction will reduce the temperature of the bottom of the target object, causing the temperature measured by the thermal imaging scope to be lower than the actual temperature of the target object.

(3) Solar radiation and illumination factors

Direct solar radiation: Solar radiation includes electromagnetic radiation in multiple bands such as visible light, infrared and ultraviolet rays. During the day, direct solar radiation will increase the surface temperature of the target object, and the absorption and reflection characteristics of target objects of different materials to solar radiation are different. This will increase the complexity of the surface temperature of the target object and interfere with the thermal imaging scope when measuring the target temperature. For example, black objects absorb solar radiation more easily than white objects, and the surface temperature rises faster. If the thermal imaging scope cannot take into account the influence of solar radiation, temperature measurement errors will occur.

Reflected light and scattered light: In addition to direct radiation from the sun, reflected light and scattered light from the surrounding environment will also affect the temperature measurement accuracy of the thermal imaging scope. For example, highly reflective surfaces such as water and snow will reflect solar radiation and thermal radiation from the surrounding environment. These reflected and scattered lights may be mistaken by the thermal imaging scope as heat signals of the target object, resulting in temperature measurement errors.

• Previous: How does the temperature measurement accuracy of thermal imaging scopes affect their performance?