Resistors play a very important role in all electrical circuits. Any electrical connection cannot be complete without a kind of resistor. The role of the resistor is to provide a resistance to the flow of current in a circuit so that the other device is not damaged by an excess current.
The two types of resistors include variable types, whose resistance changes with time and temperature, and fixed resistors which have a fairly constant value of resistance. With the technology changing and advancing every day, there has arisen a need for a third category of resistors, the custom resistors. Custom resistors are produced to work on custom-made devices. The fact that they are very precise and accurate when in operation is the reason they are also referred to as the precision resistors. Certain factors determine the kind of custom resistors chosen for particular circuits. A few of these factors are described here.
Amount of resistance needed in the circuit. Before you select a custom resistor to use in an electronic device, you ought to know the amount of resistance which is necessary for that particular circuit. This value of total resistance is the amount of resistance that should be supplied by the resistor chosen. Resistance is value is given in Ohms and is measured using an ohmmeter. Selection of a custom resistor to fit into the circuit can only be known after measuring the resistance.
Another factor that determines resistor choice is the power rating of the resistor. The amount of electrical power lost by the resistor in Watts is referred to as the power rating of the resistor. The amount of resistance, voltage and current flowing through an electrical circuit will determine the amount of power in the circuit. Amount of power is computed as the value obtained by dividing the square of voltage by the resistance. So, once the two values of voltage and resistance are known, power rating for the resistor is calculated, and this information is used when choosing the custom resistor to fit the circuit.
You also have to factor in resistor construction when selecting a custom resistor. Construction in this regard has to do with the type of material used to make it. Custom resistors are normally produced from different kinds of materials. Carbon composition, metal films, thick and thin films as well as foils are some of these materials. The material used in making a resistor will dictate how it will resist the current in the circuit.
How the resistor is mounted in the circuit. The style in which the resistor is to be mounted into the circuit is also an important consideration to have in mind. The different kinds of mounting for resistors include surface mount, PC mount, panel mount or bracket mount. The custom device into which the resistor is to be included is the one that determines the kind of mounting adopted. You have to ensure that you get the proper resistor to fit the mounting technique on your circuit.