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A Dependent on the application, the electrical engineer specifies different properties of the resistor. The primary purpose is to limit the flow of electrical current; therefore the key parameter is the resistance value. The manufacturing accuracy of this value is indicated with the resistor tolerance and is expressed as a percentage of the resistance value (for example ±5%). Many other parameters that affect the resistance value can be specified, such as long term stability or the temperature coefficient. The temperature coefficient, usually specified in high precision applications, is determined by the resistive material as well as the mechanical design. 

In high frequency circuits, such as in radio electronics, the parasitic capacitance and inductance can lead to undesired effects. Foil resistors generally have a low parasitic reactance, while wirewound resistors are among the worst. For accurate applications such as audio amplifiers, the electric noise of the resistor must be as low as possible. This is often specified as microvolts noise per volt of applied voltage, for a 1 MHz bandwidth. For high power applications the power rating is important. This specifies the maximum operating power the component can handle without altering the properties or damage. The power rating is usually specified in free air at room temperature. Higher power ratings require a larger size and may even require heat sinks. Many other characteristics can play a role in the design specification. Examples are the maximum voltage or the pulse stability. In situations where high voltage surges could occur, this is an important characteristic. 

Sometimes not only the electrical properties are important, but the designer also has to consider the mechanical robustness in harsh environments. Military standards sometimes offer guidance to define the mechanical strength or the failure rate.

A Resistance of resistor changes with temperature; and TCR stands for temperature coefficient of resistance, which indicates that when temperature changes by 1℃, the relative change of resistance in ppm/℃. Resistance will return to initial value with temperature returns to normal temperature. Calculation formula:

A Jumper resistor is also known as 0Ω resistor. ① In circuit design, the power supply can be separated as multiple channels with 0Ω resistor for commissioning or compatible design. ② It can be used as jumper. If certain section of the line is not used, just simply attached a 0Ω resistor (appearance will not be affected). ③ When the parameter of the matching circuit is uncertain, it can be replaced by 0Ω first and replace it with component with specific value during commissioning. ④ When wiring is impossible, you can also add a 0Ω resistor. ⑤ Under high-frequency signal, it can act as inductor or capacitor (related to the characteristics of external circuit) for dealing with EMC problems. ⑥ Used for cross-over connection of current circuit to provide shorter returning path and reduce interference. ⑦ Sometimes, user will change settings during circuit configuration. In order to reduce maintenance cost, 0Ω resistor can be used as alternative of jumper and welded on board. The actual resistance of a 0Ω resistor is not zero, the definition of which is ≦50mΩ (or ≦20mΩ). Therefore, parts with ±1% or ±5% share the same specifications. For functional perspective, jumper resistance dose not require precision. What user needed is the maximum rated current (i.e. current allowed to pass) instead of cannot be purchased or produced.

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