The Pros and Cons of Making Use of Carbon Film Resistors

Exactly what is a carbon film resistor?

It's a resistor made of a film of carbon placed on a substrate. Moreover, helical cuts are made in the said

film in order to produce diverse resistance values.

Carbon film resistors are designed for both high voltage and high temperature purposes. Simply by

breaking down hydrocarbon gases at extremely high temperatures; this resistor can be made. In

addition, they are created in a vacuum. Out of this process, a formation of carbon deposit on a substrate

transpires. The process is completed by heating methane or propane gas. This technique is known as

high temperature pyrolysis. Hydrogen gas is then produced due to molecular condensation when the

heat is applied that will bring about the end result: carbon.

Greater resistance is generated with the use of a spiral which will reduce the width of the film and at

once, expand the length. There are several resistances which can be created together with assortment

of types and resistivity of carbon. Carbon film resistors possess a maximum power range between 1/8 W

to 2 W at 75 degrees Celsius. And the resistance can vary from somewhere around 1 ohm to 10M Ohm.

The operating temperature of this carbon film resistor varies from -45 to 150 degrees Celsius. With

regards to voltage range, these resistors vary from 150 - 400 volts maximum.

The Pros

The greatest thing about this carbon film resistor is that these elements are very affordable and at the

same time, has the capacity to endure high voltages and high temperatures. Special carbon film resistors

really exist, of which the highest voltage that the device can function is up to 15kV. You may also get

types having a maximum operating temperature of 350°C. They can even be found in distinct tolerances

of 5 to 20 %. These variety in tolerances are made from cutting a helical grove. The required resistance

value is obtained by regulating the pitch of the helix. Normally, the thinner the carbon layer and the

finer the pitch of the helix, the higher the resulting resistance value will be. Distinctive alloy contact caps

and tinned electrolytic copper connecting wires are pressed to the ends of the resistor body following

the cutting of the helix or spiraling. Covering or coating is then the very last step where in it involves

quite a few layers of lacquer, epoxy, or by using a glass film as protective shielding. This coating is

conducted mostly for electrical insulation and as well as shielding from the climate.

The Disadvantages

Carbon film resistor definitely has many positive aspects but of course, it also has a handful of

disadvantages. To begin with, they are confined to about 1 % accuracy. Also, they exhibit drift relating to

temperature and climate. Depending on the resistant value, the resistors can have a TCR (temperature

coefficient of resistance) range of -250 to -1000 ppm/°C. Obviously, advantages still outweighs the

drawbacks especially when considering some distinct applications.

Figuring out its Uses:

These carbon film resistors can be employed in a lot of products and they are generally a great general

purpose resistor. Actually, they are the most manufactured axial leaded resistors at the moment. One of

the major advantages is it’s affordability in comparison to metal film resistors. When compared with

other types, the purposes of carbon film resistors are unquestionably more ideal. Useful applications of

these resistors can be found in gas discharge lamps, test equipment, electrical appliances, and high

voltage power supplies.