Metal oxide film resistor definition
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The metal oxide film resistor is a type of fixed resistor, which uses metal oxide film as the resistive element to limit the flow of electric current to certain level.
What is metal oxide?
Metal oxide is a metallic compound, which is formed because of the chemical bonding between the oxygen atom and other elements. Metallic compound consists of two or more different types of atoms such as (tin with oxygen). In metal oxide film resistors, the film is constructed by using the tin oxide.
What is tin oxide?
Tin oxide is a type of metallic compound, which is formed because of the chemical bonding between the oxygen atom and tin.
Metal oxide film resistor construction
The construction of metal oxide film resistor is almost similar to the metal film resistors. The main difference between the metal oxide film resistor and the metal film resistor is material used for constructing the film.
In metal film resistor, the film is constructed by using the metals such as nickel chromium whereas in metal oxide film resistors, the film is constructed by using the metal oxide such as tin oxide.
The metal oxide film resistor is made by coating the ceramic core with metal oxide such as tin oxide. The antimony oxide is added to the tin oxide to increase its resistivity. The resistivity of the metal oxide film is mainly depends on the amount of antimony oxide added to the tin oxide.
The film made of tin oxide and antimony oxide acts as the resistive element to the electric current. Hence, metal oxide film restricts the electric current to certain level. The ceramic core acts the insulating material to the electricity. Hence, the ceramic core does not allow heat through it. Thus, these resistors can withstand at high temperatures.
The metal end caps are fitted at both ends of the resistive element. The leads made of copper are joined at two ends of these metallic end caps. The metal oxide film resistors are able to withstand at higher temperatures than metal film and carbon film resistors.
In metal oxide film resistor, the desired resistance is achieved by cutting the metal oxide film in a helical manner along its length. Once the desired resistance value is achieved, the cutting of metal oxide film is stopped. Lasers are generally used to cut the metal oxide film in a helical manner.
Resistance of metal oxide film resistor is depends on the amount of antimony oxide added, the thickness of metal oxide film layer, and the width of helical metal oxide film cut
The resistance of the metal oxide film resistor is depends on the amount of antimony oxide added to the tin oxide, the thickness of the metal oxide film layer, and the width of helical metal oxide film cut.
Amount of antimony oxide added
The antimony oxide is added to the tin oxide to increase the resistance of the metal oxide film. The resistivity of the metal oxide film is directly proportional to the amount of antimony oxide added.
If large amount of antimony oxide is added to the tin oxide, the resistance of the metal oxide film to the electric current increases highly. Therefore, a large amount of electric current is blocked.
If small amount of antimony oxide is added to the tin oxide, the resistance of the metal oxide film to the electric current increases slightly. Therefore, only a small amount of electric current is blocked.
Width of helical metal oxide film cut
Cutting the metal oxide film in a helical manner with laser will increase the resistive path of the electric current. Hence, the resistance to the electric current increases. The resistance provided by the metal oxide film resistor is depends on the width of metal oxide film cut.
The helical film cut with more width provide less resistance to the electric current because the free electrons have to travel only a small distance through the resistive path. Hence, the possibility of free electrons collision with the atoms is less. Thus, only a small number of free electrons collide with the atoms and the remaining large number of free electrons moves freely from one place to another place by carrying the electric current.
Therefore, the metal oxide film resistors with wide helical metal film cut allows large amount of electric current.
The helical film cut with less width provides more resistance to the electric current because the free electrons have to travel a large distance through the resistive path. Hence, the possibility of free electrons collision with the atoms is high. Therefore, a large number of free electrons collide with the atoms and the remaining small number of free electrons moves freely by carrying the electric current.Metal oxide film layer
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The helical film cut with less width provides more resistance to the electric current because the free electrons have to travel a large distance through the resistive path. Hence, the possibility of free electrons collision with the atoms is high. Therefore, a large number of free electrons collide with the atoms and the remaining small number of free electrons moves freely by carrying the electric current.Therefore, the metal oxide film resistors with narrow helical film cut allows only a small amount of electric current.
The resistance of the metal oxide film resistor is inversely proportional to the thickness of the metal oxide film layer.
Metal oxide film resistors with very thick film provide large space for the free electrons to move freely from one place to another place. Hence, the possibility of free electrons collision with the atoms is very less. Therefore, only a small number of free electrons collide with the atoms. The small number of free electrons, which collides with the atoms, loses their energy in the form of heat and the remaining large number of free electrons moves freely from one place to another place by carrying the electric current. Therefore, the metal oxide film resistors with very thick film layer allows large amount of electric current.
Metal oxide film resistors with very thin film provide less space for the free electrons. Hence, the possibility of free electrons collision with the atoms is high. Therefore, a large number of free electrons collide with the atoms. The large number of free electrons, which collides with the atoms, loses their energy in the form of heat and the remaining small number of free electrons moves freely by carrying the electric current. Therefore, the metal oxide film resistors with very thin film layer allow only a small amount of electric current.
Advantages of metal oxide film resistors
The first alternative to a carbon composition resistor is a metal oxide film resistor. These resistors are very easy to manufacture as compared to metal film resistors. Firstly we have to know that metal oxide is one kind of metallic compound that is formed due to the chemical bonding among the oxygen atom as well as other elements. So it includes a minimum of two or above different kinds of atoms like a tin with oxygen. Thus, tin oxide is utilized for designing these resistors. These resistors are the most frequently used resistors because they have superior performance as compared to carbon film & carbon composition resistors. So this article discusses an overview of a metal oxide film resistor, it's working, and its applications.
Metal oxide resistor definition is; the fixed value and axial resistors which are made with the ceramic rod that is covered with a metal oxide thin film like tin oxide are known as metal oxide film resistor. These resistors should not be confused with metal oxide varistors because they are made with silicon carbide or zinc oxide. These resistors are used mostly wherever power dissipation is necessary. The metal oxide resistor diagram is shown below.
The performance guide of the metal oxide film resistor is given below.
The metal oxide film resistor construction is the same as the metal film resistor except for the material used to construct the film. This resistor uses tin oxide to construct the film which is made with tin oxide as well as antimony oxide which works as the resistive element for the electric current. Thus, this material restricts the current flow to a certain level.
The manufacturing procedure of a metal oxide film can be done with chemical deposition techniques & almost ceramic carriers are used as substrates always. The deposition procedure is obtained by the pure metals reaction with gas at low pressure & high temperature. The metal oxide film is most frequently produced with a chemical deposition process. Here tin oxide is the common metal oxide film that is created by heating the body of this resistor within a tin chloride steam.
Usually, other metal oxide film uses a different deposition procedure. Initially, a thin metal film is applied, after that it is reacted by oxygen. So the desired composition is attained by simply measuring the resistance.
The working of this resistor is; once the film is applied to the body of the resistor then the final value of resistance can be achieved by applying a helical cut. Usually, this can be done by laser cutting but earlier it was done by sandblasting or grinding. Here, the spiral cut on the resistor will make the resistance path longer & also increases the value of resistance up to a hundred times higher. The value of resistance can be controlled precisely by cutting. The resistance of his resistor mainly depends on the antimony oxide amount of added to the tin oxide; the helical metal oxide film cut width & the metal oxide film layer thickness.
The characteristics of a metal oxide film resistor are given below.
Generally, cylindrical resistors are color coded with bands/markings to identify the values of resistance & tolerance very quickly like metal film, carbon film, fuse, winding, metal film, and metal oxide film resistors. So the resistance value can be found based on the color code of the resistor. Resistors are available in four to six color bands on the resistors which specify the value of resistance.
Please refer to this link for: Resistor Color Code.
Please refer to this article for the Difference between Metal Oxide Resistor & Metal Film Resistor.
The advantages of a metal oxide film resistor are discussed below.
The disadvantages of a metal oxide film resistor are discussed below.
The applications of a metal oxide film resistor are discussed below.
Thus, this is an overview of a metal oxide film resistor ' working, characteristics, advantages, disadvantages, and its applications. This is a fixed-type resistor that uses a resistive element like metal oxide film to restrict the electric current flow to a certain level. Here is a question for you, what is a carbon film resistor?