Parameters of Carbon Film Resistors | Hacker Noon

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@rachelanne2020RachelAnne2020

An electronic editor working in electron industry.

Carbon film resistors are a type of film resistor. It uses high-temperature vacuum coating technology to closely attach carbon to the surface of the ceramic rod to form a carbon film. Then appropriate joints are added for cutting, and the surface is coated with epoxy resin for sealing protection. The surface is often painted with green protective paint.

The thickness of the carbon film determines the size of the resistance, and the thickness of the film and the notch are usually used to control the resistor.

Carbon film resistors are also called “thermal decomposition carbon film resistors”, which is a kind of thin-film resistor in which carbon is deposited on the substrate by the high-temperature thermal decomposition in a vacuum. It has low price, stable performance, wide resistance and power range.

Error Rate of Carbon Film Resistor

The error rate of carbon film resistors is generally divided into three levels: the error rate of level I is 5 [%], the error rate of level II is 10 [%], and the error rate of level III is 20 [%]

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 carbon film resistor with a resistance value of 47kΩ, and an allowable deviation of ± 5 [%] .

The rated power of the carbon film resistor is not 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 three leading methods of axial leads, tie leads, and unconnected leads.

The resistance range of carbon film resistors is 1Ω~10MΩ. Rated power is 0.125W, 0.25W, 0.5W, 1W, 2W, 5W, 10W, etc.

Main Parameters of Carbon Film Resistors

Nominal Resistance Value: The resistance value marked on the resistor is called the nominal value. The unit is expressed in ohms (Ω). It includes Ω (ohm), KΩ (kiloohm), and MΩ (megaohm). The conversion relationship is: 1MΩ=1000KΩ, 1KΩ=1000Ω.

The nominal value is marked according to the standard series formulated by the country, not arbitrarily marked by the manufacturer. Not all resistors have this value. The resistance range of carbon film resistors is 1Ω~10MΩ.  

Allowable Error: The maximum allowable deviation range of the actual resistance of the resistor from the nominal value is called the allowable error.

Error Code: F, G, J, K   

Rated Power: refers to the allowed power consumption of the resistor in a long-term continuous operation without damage or the resistor performance does not change under the specified ambient temperature, assuming that the surrounding air does not circulate. 

The rated power of carbon film resistors is not 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 are generally rated at 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-sized resistor devices, small-scale carbon film resistors of RTX type have been produced, with a power of only 0.125W, and most of them are made into color code resistors.

The greater the resistance of the conductor, the greater the resistance of the conductor to the current.

Also published on: Basic Introduction about Carbon Film Resistors

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