As we have already discussed the electrical resistance in detail in the previous article, we shall proceed with the discussion on different type of resistors.
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Carbon Composition
It is a type of resistor, which is a combination of particles of carbon and a binding resin with varying proportions of each which provides the desired resistance. Caps of metal are connected to both ends of the resistive element which have the extruding leads of tinned copper wire for the purpose of soldering the resistor to any circuit. The resistor is enclosed in a plastic case which acts as a barrier to entry of moisture and other harmful external elements. Carbon composition resistors are used in the electronic industry extensively in all major circuits. They are available in different power ratings of 1/8, 1/4, 1/2, 1, and 2 W, as well as in different voltage ratings of 250, 350, and 500 V. These resistors have low failure rates subjected to proper usage.
These type of resistors produce electric noise due to the current passing from one carbon particle to another. This noise appears as a hiss in a loudspeaker connected to a hi-fi system and can mostly overcome very weak signals. This is the reason for the use of carbon composition resistors where the performance requirements are not demanding and where low cost is the main consideration of selection. Hence, they are extensively used in media electronics circuits.
Deposited Carbon
A deposited carbon resistor is among the type of resistors, that consist of ceramic rods which have a carbon-deposited film on top of it.
They are constructed by inserting a ceramic rod in a flask filled with methane and heating it utilizing the gas-cracking process until a layer of carbon film is deposited over it. The helical grinding made on the body forms the path of resistance. Also as compared to the carbon composition resistors, these resistors offer a major improvement in lower current noise in close tolerance. These resistors are being replaced mostly by the use of superior metal film and metal glaze resistors.
High-Voltage Ink Film
These resistors are among the type of resistors that consist of a ceramic base on which a special resistive ink is laid down in a helical band. These type of resistors can easily withstand large voltage levels and find its extensive use in major circuits dealing in high voltages like in circuits of radars, and medical electronics circuits. The resistances of these resistors range from 1 kΩ to 100,000 MΩ with voltage ranging up to 1000 kV.
Metal Film
Metal film resistors are type of resistors which are made by depositing vaporized metal in vacuum on a ceramic-core rod.
The resistive path is helix-groove also as in the case of the deposited carbon resistors. Metal film resistors are unique as it has an excellent temperature tolerance capability and temperature coefficient making them extremely reliable resistors. Hence, they are very suitable for various high-grade applications and also used in low-level stages of certain instruments however, they are much more costlier.
Metal Glaze
A metal glaze resistor is a type of resistors that consists of a metal-glass mixture which when applied as a thick film to a ceramic substrate and fired, turns the film, glazing. The value of resistance depends on the amount of metal in the mixture. With the alteration in the helical formation grinding, the resistance of these type of resistors can be made to vary from 1 Ω to several megaohms. Many metal glaze resistors also contain a tinned oxide film on a glass core.
Wire-wound
Wire-wound resistors are type of resistors that are different from all other types in the sense that no film or resistive coating is used in their construction. It consists of a core of ceramic that is wound by drawn wire with precision-controlled characteristics. Different alloys used in this wire provide different ranges of resistance. It is the type of resistors which have the highest stability along with the highest power rating.
Because of the bulk, high-power ratings, and increased cost, they are leanly suitable for low-cost or high-density, limited-space applications. The completed wire-wound resistors are mostly coated with baked enamel, which provides good insulation.
Cermet (Ceramic Metal)
The cermet resistors are type of resistors which are made by firing certain metals blended with ceramics on a ceramic substrate. The range of resistance of cermet resistors depends largely on the blend of the mixture of metal and ceramics and also on the thickness. These type of resistors can achieve precise values of resistance along with high stability even under extreme temperatures. Usually, they are manufactured as tiny rectangles with extruding leads to enable the attachment to printed circuit boards (PCB).
