Everything You Need To Know About Carbon Film Resistor

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There are different types of resistors used for the electronics applications.

They are usually ranked according to the type of material used, or the resistive material.

These materials include tungsten, brass, Nichrome and platinum.

Due to the fact that these metals have less resistivity, carbon has always proven to be a viable alternative for the resistors.

It is ranked among the most common types, perhaps due to the numerous desirable  features that it has.

Carbon resistors come in different physical and technical specifications.

Are you planning to buy carbon resistors for your application? Here is a perfect guide for you. We are going to break down everything you should know about carbon resistors.

We will also give you tips for buying the best carbon resistors for sale.

Definition of carbon film  resistor

This is a type of resistor that uses carbon film  as its resistive element. The resistor relies on this material to inhibit the flow of electric current.

A thin film of carbon is deposited on the ceramic rod  in the right proportions depending on the desired performance of the resistor.

Carbon film resistors are used in many different types of circuits including the audio circuits and as well as the amplifier circuits.

In terms of the physical appearance, a typical carbon film resistor has a cylindrical shape and sports different colors such as gray with gold or silver bands at the ends. It also has the value of the resistor indicated at the end. There could be a slight variation of the  resistor design depending on the manufacturer.

Accuracy and reliability are among the top reasons behind the popularity of these resistors.

They also tend to perform pretty well even when exposed to different environmental conditions, such as high temperatures.

Construction of carbon film resistor

What does the carbon film resistor construction entail?

These resistors are constructed  by depositing the carbon film resistive element into an insulating core. The resistive element is then encased in the insulating material so that it does not leak or get exposed to impurities.

The encasing material can be a ceramic tube that has two metal caps at its end. The caps are usually made of different materials such as nickel, tin or copper. These connect the resistor to the rest of the circuit.

The volume of the resistive material inside the insulating material will determine the resistance value. During the construction process, a carbon film resistor manufacturer can adjust the helical path of the resistor to determine the ultimate resistance.

The width of the carbon film will also have a direct impact on the resistance value. For example, a thin layer will result in maximum resistance value since less electrons are likely to pass through.

On the other hand, a thick width means less resistance to the flow of electrons. This means that more electrons will have a chance to flow.

Another key factor that is considered during the carbon film resistor construction is the negative temperature coefficient. (NTC). This is the temperature at which the resistance value of the material starts decreasing.

How does a carbon resistor work?

The working principle of a carbon film resistor is based on the fact that when a stream of electric current passes through the carbon film substrate, there will be a significant increase of  resistance to the flow of the current.

At the same time, there will be a temperature increase of the resistor creating a positive  temperature coefficient (PTC).

The resistance of the carbon film will always change with a small change of the supply voltage. This is what is usually referred to as the voltage coefficient(VC).

As the current passes through the carbon film resistive material, they will randomly collide with each other hence transferring energy to the atoms in the film. These constant vibrations are responsible for creating resistance to the normal flow of electrons.

The  level of resistance in the carbon film will depend on several factors among them the thickness of the film, purity of the carbon material, length of the carbon film among others.

Carbon film resistor manufacturers usually indicate the resistance value on the surface of the resistors and is expressed in terms of ohms Ω. Carbon film resistors have a tolerance value which ranges between 2% to 20%. This value varies depending on the purity of the carbon material and of course thickness of the material.

Temperature also has a direct impact on the working operation of the carbon film resistors.   An increase of temperature leads to a decrease in temperature. The good thing about carbon film resistors is their high negative temperature coefficient.

Carbon film resistors technical specifications

Here are the key technical specs that you should know about carbon film resistors.

-Power rating: Between 0.125W to 5W

-Operating temperature : -55 to +155ºC

-Resistance value of between  1 ohm  up to 10 megaohms

-Maximum operating voltage of between 200 volts to 600 volts

-Maximum noise level of up to 20µV/V

-Voltage coefficient of 0.0005%/V

Understanding the carbon film resistor color codes

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Still on the technical aspects, it is important to understand the carbon film resistor color codes.

The color bands indicate the resistance and even tolerance of a particular resistor.

So, what do the color bands on these resistors mean?

First,  a carbon resistor can have between  3 to 6 bands of colors

The first two color bands indicate the resistance value of the resistor.

The third band is used as a multiplier while the fourth band defines the tolerance of the resistor.

Take note that the fourth band is usually separated from the  other three color bands.

If you are not sure, it will always be advisable to seek an expert’s help when it comes to differentiating the color bands of a carbon film resistor. Or, you can just check out the carbon film resistor datasheet for clarification.

Advantages of carbon film resistor

Are you planning or even considering to buy and use carbon film resistors for sale? Here are the top advantages that you are likely to gain.

-Low noise: Noise in this context refers to the electrical interference that are likely to affect the operation and performance of the resistor. Carbon film resistors are rarely affected by this electrical noise.

-Affordable: These resistors tend to win when it comes to the affordability contest. The cost of carbon film resistors is lower than most of the alternatives.

-Small and compact: The small size of these resistors means that you can install and use them in small projects. You wont have to worry about the space required.

-Wide operating temperature: A key feature that allows the carbon resistors to work perfectly in different environmental conditions.

-High accuracy: Carbon film resistors are popular mainly because of their accuracy. They have zero room for error.

-Excellent reliability: You can fully rely on these resistors when it comes to performance and even durability. They have a considerably long lifespan.

-Easily available: These resistors are everywhere and you can easily find one that fits your  application. However, ensure that you buy from reliable carbon film resistor suppliers, that is if you want quality products.

Disadvantages of carbon film resistors

The cons of a carbon film resistor include:

-High negative  temperature coefficient(NTC): This means that the resistance of these resistors can easily change with the slightest change of temperature.

-Lower capacity than most resistors in the same category

-Poor temperature stability: It is difficult for these resistors to remain stable when the temperatures keep varying.

Applications of carbon film resistors

Some of the application areas of these resistors include:

• High-voltage power supplies
• Amplifiers
• Voltage and current filters
• Lighting systems
• Audio systems
• Motor controls

You can use these resistors in applications that require the highest accuracy of resistance. Also, the ability to cut out noise makes them suitable for the audio systems such as amplification.

The ability of these resistors to operate in a wide temperature range gives them an upper hand when it comes to high-voltage applications.

Where to buy carbon film resistors?

To get the full benefits of carbon film resistors, you should pay attention on the source; where you buy.

This can be the manufacturers and suppliers of the carbon film resistors.

Since there are different brands of these resistors, ensure that you buy from the most reputable manufacturers. This way you can be sure of getting high-quality resistors.

The same rule applies when buying from the carbon film resistor suppliers or sourcing agents.

They should be reputable and reliable.

The good news is you can easily find reputable carbon film resistor suppliers in China, if you are patient enough.

Conclusion

Carbon film resistors have proven to be efficient and highly reliable. They can fit into different applications and deliver the desired results.

Since they have different resistance values, you should verify the value before buying one.

And  when it comes to buying, whether it is for sale or you want carbon film resistors in bulk, choose ICRFQ as your reliable suppliers in China.

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