Difference Between Carbon Film & Metal Film Resistors

Resistors are electronic devices that are designed to impede the flow of current running through their bodies, allowing for the protection of sensitive electronics while also opening up the opportunity to control and manage voltage values for specific applications. As a technology that was first invented in 1959, resistors now serve almost all electrical circuits. With a variety of resistor types featuring different constructions, materials, tolerance values, and other characteristics, finding the correct type often depends on the specific needs of the operation. In this blog, we will discuss the carbon film and metal oxide film resistor in particular, allowing you to best understand the differences between two very common electrical circuit components.

Carbon film resistors are a type of film resistor, meaning that they are constructed through the deposition of oxide film or pure metals onto an insulating ceramic or substrate. Through an application method known as sputtering, the layer of film on the resistor can be made very thin. For carbon film resistors in particular, carbon film is sputtered onto an insulated ceramic substrate. As the flow of current is mitigated by the ceramic insulation, such resistors can undertake large amounts of heat without risking damage or failure. Despite this, the resistance of the component is directly tied to temperature, as more heat will decrease the resistance of the component. As such, carbon film resistors are often available with tolerance values ranging from 1 Ohm to 1 Mega Ohm. With their cost-efficiency and low tolerance, they can be used in a variety of applications such as power supplies, lasers, radar systems, and x-rays.

Unlike the carbon film resistor, metal oxide film resistors feature thin metal oxide film that encapsulates an insulating ceramic rod. With tin oxide paired alongside antimony oxide materials, the film of the component provides good resistance values. As the metal oxide film resistor takes advantage of a ceramic rod with insulation, it can withstand high amounts of heat by deterring its flow. Additionally, this also ensures that current is reduced, and the ratio of antimony within the film will dictate resistance values. Nevertheless, the metal oxide’s thickness and the width of its cut will also affect resistance values. Similar to carbon film resistors, the metal oxide film resistor is quite low in cost and can withstand high temperatures. With the addition of optimal reliability and stability, metal oxide film resistors can be found in a variety of electrical circuits within telecommunication systems, medical equipment, and more.

As carbon film and metal oxide film resistors seem quite similar in their capabilities, choosing between the two can sometimes be difficult. When it comes down to voltage and temperature coefficients, metal oxide film resistors are typically more powerful. With the metal oxide film type, higher temperatures can be handled with a wider resistance range. As such resistors can keep current values low, the noise that emits from the component is also minimal. Furthermore, metal oxide film resistor tolerances can reach as low as 0.1% as compared to the 2% value achievable by carbon film. Nevertheless, carbon film resistors can be much cheaper, making the decision a matter of what is specifically required for a given application and monetary constraints.

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