An Informative Guide on the Carbon Composition Resistor
The carbon composition resistor is one of the most basic resistor types that one may procure, having first been designed and developed during the early 1960s. Containing a solid cylindrical resistive element and lead wires attached to metal end caps or embedded wire leads, the carbon composition resistor is non-inductive for the benefit of surge protection and voltage pulse reduction applications. While carbon composition resistors have since been superseded by other resistors for numerous applications, they still find use in power supplies, welding controls, vintage electronic devices, and other settings. In this blog, we will discuss the carbon composition resistor in more detail, allowing you to have a better understanding of their design and functionality.
Carbon composition resistors are considered to be a fixed resistor, meaning that their resistance values remain constant regardless of voltage or temperature fluctuations. As such, they are primarily relied on for the restriction or reduction of current to reach a specific value. In order for the resistance capabilities of a carbon composition resistor to be set, factors such as carbon quantities, the length of the solid cylindrical rod, and the cylindrical rod cross-sectional region can be altered during the manufacturing phase.
As mentioned before, the carbon composition resistor is made from a resistive element, which is made from a mixture of carbon powder and insulating materials such as ceramic. In order to attain a particular resistance value, one must control the ratio of carbon powder in relation to the insulating material. Generally, if one wishes to have less resistance and high conductivity, then they will want to minimize the amount of insulating materials that are implemented so that a high concentration of carbon is achieved. Meanwhile, prioritizing the insulating materials with a low carbon powder count will have the opposite effect as resistance is bolstered. While the ratio of carbon powder and insulating materials is crucial, other factors such as internal moisture content can also have an effect on resistance as heat causes non-reversible resistance value changes.
Once the resistive element is established, leads of embedded wire are attached to each side before the entire body is encapsulated within paint or plastic for ample protection. To guard the lead wires, the sections near the ends of the resistive element rod are covered and soldered. As many carbon composition resistors have very similar appearances in their final state, manufacturers will regularly implement color-coding to denote values, all of which follow a standardized system.
While carbon composition resistors may be considered to be somewhat obsolete in various applications, they are still useful for certain needs. Generally, carbon composition resistors are fairly available on the market, and their resistance values often range from 1 ohm to 10 megaohms. For tolerance, meanwhile, such resistors are often available with ±5%, ±10%, and ±20% values. As it is important to know the temperature ranges of components for their safety, the maximum temperature of a carbon composition resistor is 120°C. Meanwhile, the temperature coefficient of the carbon composition resistor is over ±1000 ppm/°C.
Despite being an older form of resistor, there are still various advantages that carbon composition resistors hold over others. Generally, carbon composition resistors are known for their ability to handle high energy pulses with ease, their compact construction that benefits constricted spaces, and their low price point. Despite this, they often generate a large amount of noise, operate with low accuracy and poor stability, exhibit small power dissipation capacity, and have sensitivity to humid environments and moisture. Additionally, carbon composition resistors should not be used for modern electronic devices that are highly sensitive due to their general characteristics.
Regardless of shortcomings, there are still many applications that can highly benefit from the use of carbon composition resistors. As a few common examples, one may find carbon composition resistor components within welding control circuits, DC power supplies, X-rays, lasers, radars, test equipment, computers, and much more. As with any resistor type, it is important that they are well-chosen before implementation, as well as regularly inspected and maintained so that aging or defective elements can be repaired or replaced before an issue ensues. If you are in the market for high quality resistor components that you can depend on with ease, One Click Aviation is your sourcing solution.
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