First, the printed circuit board temperature
1. Printed board temperature definition
Temperature is customarily defined as a feeling of warmth and coldness that comes into contact with an object. If two objects are put together (physically called thermal contact), then a high-temperature object will transfer heat to a low-temperature object until the temperature between the two is equal, that is, between the two objects. Thermal equilibrium. At this point we will feel that the temperature of the two objects is the same. We can define the temperature of the system as when the two objects reach thermal equilibrium.
If we further understand the two systems, we will find that multiple systems will reach thermal equilibrium with each other. Thermal balance does not depend on the type of object but on the system in which they are located.
The law of thermodynamics tells us that in two thermodynamic systems, if each is in equilibrium with the third system, they are in thermal equilibrium with each other. That is, all systems that are in thermal equilibrium have the same temperature.
You feel cold and hot with your hands on the object, and when you identify the heat with your eyes, you will feel dull and reddish, and the temperature is bright and dazzling. These methods of contact and non-contact hot and cold degrees are still in effective use today. No matter whether the thermometer is measured by direct or indirect comparison, the thermometer is designed based on the principle of heat balance.
2. Printed circuit board temperature measurement
In the early development of resistance thermometers, Callendar studied platinum resistance thermometers. Since then, resistance temperature measurement has undergone great changes. The platinum resistance thermometer, a classical platinum resistance thermometer for high-precision measurement, has continuously expanded its temperature measurement range. For the most accurate temperature measurement, a platinum resistance thermometer is always the most preferred thermometer. Pure platinum is selected as the resistance thermometer component material is determined by its own nature: chemical stability, stability is good even at high temperatures; high melting point, easy to obtain filament under high purity conditions; high resistivity ( It is approximately 10 μΩ.cm) at room temperature. The ductility is good for drawing filaments, but it also brings some difficulties. The completely annealed platinum wire is very soft and will encounter some problems in the installation process. Platinum has a strong antioxidant capacity at high temperatures, making it a very good material for measuring high temperatures. Platinum is not only a good resistance thermometer material, but also a good high-temperature thermocouple material.
The resistance-temperature relationship of platinum resistance thermometers, as theoretically expected, is that the resistance of platinum resistance thermometers is fairly close to the square function of temperature over a wide temperature range extending from room temperature.
Second, the printed circuit board humidity
1. Absolute humidity of printed circuit board
The mass of water vapor contained in every 1m3 of humid air is called the absolute humidity of wet air. Therefore, the absolute humidity T is numerically equal to the temperature of the moist air and the partial pressure Pv of water vapor. The density Ïv of the water vapor can be determined by the water vapor meter.
2. Printed circuit board relative humidity
The amount of water vapor in the atmosphere can vary between O and saturation. The absolute humidity only represents the actual water vapor content in the moist air, and cannot explain the degree of saturation of the moist air or the capacity of absorbing water vapor in this state. Therefore, the relative humidity is often used to express the degree of moisture in the moist air.
1. Printed board temperature definition
Temperature is customarily defined as a feeling of warmth and coldness that comes into contact with an object. If two objects are put together (physically called thermal contact), then a high-temperature object will transfer heat to a low-temperature object until the temperature between the two is equal, that is, between the two objects. Thermal equilibrium. At this point we will feel that the temperature of the two objects is the same. We can define the temperature of the system as when the two objects reach thermal equilibrium.
If we further understand the two systems, we will find that multiple systems will reach thermal equilibrium with each other. Thermal balance does not depend on the type of object but on the system in which they are located.
The law of thermodynamics tells us that in two thermodynamic systems, if each is in equilibrium with the third system, they are in thermal equilibrium with each other. That is, all systems that are in thermal equilibrium have the same temperature.
You feel cold and hot with your hands on the object, and when you identify the heat with your eyes, you will feel dull and reddish, and the temperature is bright and dazzling. These methods of contact and non-contact hot and cold degrees are still in effective use today. No matter whether the thermometer is measured by direct or indirect comparison, the thermometer is designed based on the principle of heat balance.
2. Printed circuit board temperature measurement
In the early development of resistance thermometers, Callendar studied platinum resistance thermometers. Since then, resistance temperature measurement has undergone great changes. The platinum resistance thermometer, a classical platinum resistance thermometer for high-precision measurement, has continuously expanded its temperature measurement range. For the most accurate temperature measurement, a platinum resistance thermometer is always the most preferred thermometer. Pure platinum is selected as the resistance thermometer component material is determined by its own nature: chemical stability, stability is good even at high temperatures; high melting point, easy to obtain filament under high purity conditions; high resistivity ( It is approximately 10 μΩ.cm) at room temperature. The ductility is good for drawing filaments, but it also brings some difficulties. The completely annealed platinum wire is very soft and will encounter some problems in the installation process. Platinum has a strong antioxidant capacity at high temperatures, making it a very good material for measuring high temperatures. Platinum is not only a good resistance thermometer material, but also a good high-temperature thermocouple material.
The resistance-temperature relationship of platinum resistance thermometers, as theoretically expected, is that the resistance of platinum resistance thermometers is fairly close to the square function of temperature over a wide temperature range extending from room temperature.
Second, the printed circuit board humidity
1. Absolute humidity of printed circuit board
The mass of water vapor contained in every 1m3 of humid air is called the absolute humidity of wet air. Therefore, the absolute humidity T is numerically equal to the temperature of the moist air and the partial pressure Pv of water vapor. The density Ïv of the water vapor can be determined by the water vapor meter.
2. Printed circuit board relative humidity
The amount of water vapor in the atmosphere can vary between O and saturation. The absolute humidity only represents the actual water vapor content in the moist air, and cannot explain the degree of saturation of the moist air or the capacity of absorbing water vapor in this state. Therefore, the relative humidity is often used to express the degree of moisture in the moist air.
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