When designing analog and digital circuits, most times it is difficult to know the finest resistor to use. We have a thousand resistors in the market today and are better than others depending on the specification for use. Various resistors have different characteristics. Resistors are elements that provide resistance to flow of electrons via a medium. They serve different function such as limiting current, setting voltage levels, manipulating circuit timing and many other applications. The different properties of resistors include voltage rating, temperature rating, temperature coefficient of resistance, tolerance and their frequency response.
Tolerance of a resistor is well-defined as how much a resistor value varies from its defined value. The parameters are defined as percentages usually one percent, five percent, and ten percent. Precision resistors are only available where tolerance falls below one percent. The voltage rating of a resistor is the actual amount of voltage that can safely dropped from corner to corner of a resistor. Power rating is the actual amount of power that can be consumed by a resistor. Power registered is usually presumed to be the normal power that a resistor can consumer rather than on the spot. As always the rule of thumb, it is well to pick a custom resistor with a power rating double of what was needed first.
The temperature rate defines the temperature limits where a resistor will function properly. Temperature co-efficient of resistance is the amount of variance exhibited by a resistor as temperature changes from twenty five degrees centigrade and is measured as parts per million (ppm). The frequency response of a resistor is defined as the change in impedance which is shown by a resistor as a function of frequency. A change in impedance as a function of frequency is sometimes desired and sometimes is not.
There are many other factors that can be considered when selecting a resistor but the top most elements to be taken into account for many basic applications are the properties that are outlined above. Most sellers who are selling resistors make it fairly easy to pick the desirable parameters. As outlined from the start, there are lots of resistors that are offered in the market, so it will be of help if you narrow down the resistors into what you what it to serve you. All these aspects are important in the total performance of the circuit.