Last Updated on October 22, 2023 by Kevin Chen
Image of carbon film vs metal film
Resistors are essential components in every electric circuit. They are designed to resist the normal flow of electric current in a particular circuit, and there are reasons why this resistance matters. Like most electronic components, resistors have undergone a series of evolution. The materials used to make resistors have also changed over the years. Currently, the most popular materials are carbon film and metal film.
So, what is the difference between carbon film resistor and metal film resistor? This article has the answer. We are going to break down the differences between the two. At the end of it all, you will know which resistor is perfect for your application.
Overview of carbon film resistors
Carbon film resistors are made when a film of carbon is deposited on the ceramic substrate. The carbon film is then stripped into helix shape so as to increase its resistive path or surface area. The carbon film resistor will be able to provide the required level of resistance to some degree. On the other hand, the insulating ceramic provides high degree of heat resistance.
The heat that is generated due to the electric resistance will not be able to penetrate through the ceramic substrate. This feature makes the carbon resistors capable of withstanding high temperatures without getting damaged.
Carbon film resistors are quite popular thanks to their low cost. Their tolerance level ranges between 5-10%, making them suitable for a wide range of applications. You will find them in different electronic circuits such as power supplies, control circuits, amplifiers among others.
These resistors come in different resistance values, tolerance ranges, power ratings, and even sizes. The application area will define the specification of the resistor that you use.
How do I identify carbon film resistor?
You can identify a carbon film resistor based on its physical features and characteristics. These resistors have a thin cylindrical body and comprise of the ceramic material and a helical groove runs along the body.
The bodies of the carbon film resistors are color-coded to indicate the resistance value and the tolerance range. The colors are positioned near one end of the resistor.
Overview metal film resistors
Metal film resistors are also used to perform the same functions as the carbon film resistors-controlling the flow of electric current in circuits.
These resistors are constructed by depositing a thin film of metal alloy such as tin oxide or nickel-chrome into a ceramic substrate. The resultant material is then chopped into helix shape to provide the required resistive path.
Metal film resistors also come in different specifications to suit the different application needs They are also used in sensitive and more demanding applications such for the medical equipment and instruments. This is majorly because of their high accuracy and tolerance levels. But you will have to pay more for the premium features that come with metal film resistors.
How do I identify metal film resistors?
Identification of the metal film resistor is just the same as that of the carbon film resistor. They also have a cylindrical body and feature a ceramic substrate. Their bodies are also color-coded to indicate their resistance values. You will need to be extra keen to differentiate them just based on their physical attributes.
Carbon Film vs Metal Film Resistors: What’s The Difference?
Image source: Student Learn
At this point, we can proceed to break down the differences between these two types of resistors.
Metal film resistor is deemed to be more accurate than the carbon film resistors. This is because the former has a tolerance range of between 1-2%. This simply implies that the value of resistance will not deviate beyond 2% of the actual value of the resistance.
On the other hand, carbon film resistors have a tolerance range of between 5-10%, a significantly wide deviation.
So, if you want a more accurate resistor, go for the metal film resistor. Keep in mind that the accuracy of a resistor will also dictate its application areas.
The temperature coefficient of a resistor refers to the change of the resistance value with the change of temperature. We can say it is the ration of resistance to the temperature change. Both carbon and metal film resistors have a rated value of temperature coefficient only that the values tend to differ.
Carbon film has a higher temperature coefficient than the metal film resistor. This implies that the resistance value on the carbon film is likely to change significantly than that of the metal film.
This factor alone means that metal film is an ideal resistor for the extreme temperature changes. It will still be able to give an almost accurate value despite the significant changes of the external temperatures.
Carbon film resistors and metal film resistors also differ in terms of their application areas. Carbon film resistors are mainly used in low to medium voltage applications. These applications include audio equipment, lighting devices and low voltage power supplies.
On the other hand, metal film resistors can work in both low to high voltage circuits. They include industrial power systems, medical equipment, aerospace, instruments among others.
When it comes to the physical size of the resistors, there is no difference. Both come in similar size packaging. When buying, you will discover that both are packaged in axial-lead packages whereby the leads extend from the needs of their cylindrical bodies.
The physical dimensions of a resistor will always depend on its resistance value and as well as the power rating. This applies to both carbon film and metal fil resistors.
Both carbon film and metal film resistors have a role to play in the electronic circuits. However, their features and characteristics separate them. Carbon film resistors are cheaper than the metal film. They also have a higher temperature coefficient However, they tend to be less accurate and relatively unstable.
Even though metal film resistors are more expensive than the carbon film resistors, they are better suited for those sensitive applications thanks to their accuracy and low temperature coefficient.
I hope that with this guide, you will be able to buy quality resistors that will be suitable for your application area.
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