Carbon film resistors are often marked with the symbol RT. R stands for resistor and T stands for carbon film. For example, an electron gun housing marked with RT47kI means that it is a resistance value of 47kΩ, and the allowable deviation is ± 5% carbon film resistors.
The rated power of carbon film resistors is no longer marked on the housing of the resistor, but is distinguished by the length and diameter of the electron gun. A resistor with a large length and a large diameter has a higher power. Carbon film resistors have axial leads, tie-type leads, and unconnected leads.
The resistance range of carbon film resistors is 1Ω~10MΩ. The rated power is 0.125W, 0.25W, 0.5W, 1W, 2W, 5W, 10W, etc.
Ordinary carbon film resistors are larger in size. In order to meet the needs of small-volume resistor devices, small RTX carbon film resistors have been produced, with a power of only 0.125W, and most of them are made of color code resistors.
Carbon film resistors have stable performance, wide resistance range, small size, high working temperature and limit voltage, strong pulse load suitability, high high-frequency characteristics, and operating environment temperature -55℃~+125℃.
Carbon film resistors are made by using organic binders to prepare a suspension of carbon ink, graphite and fillers, coating them on an insulating substrate, and then polymerizing them by heating. Gaseous hydrocarbons decompose in high temperature and vacuum, and carbon is deposited on the porcelain rod or tube to form a crystalline carbon film. By changing the thickness of the carbon film and the length of the carbon film with the method of notching, different resistance values can be obtained. Carbon film resistors have low cost, poor electrical performance and stability, and are generally not suitable for general-purpose resistors. But because it is easy to make a high resistance film, it is mainly used as a high resistance high voltage resistor. Its purpose is the same as that of high-voltage resistors.
The reason why the resistor can reduce voltage and limit current is mainly because the resistor is an energy-consuming element. When current flows through the resistor, it consumes electric energy and generates heat, that is, part of the electric energy is converted into heat energy and digested. Therefore, in actual circuits, we often see the form of the resistor being loaded.
A resistor is a frequency-independent element, which means that no matter the same resistor in a circuit of any frequency, the resistance value is the same. Not only that, the resistance values of resistors in DC circuits and AC circuits are also the same. Therefore, for many electronic components, resistor circuits have relatively simple characteristics and relatively simple analysis.