![]() ![]() The E12 range with its 10% tolerance therefore has 12 values per decade. This range of values is called a decade, and the next higher range (decade) in the E12 series covers values between 90Ω (100Ω -10%) and 902Ω (820Ω +10%) and so on. The E12 series is so called because 12 ‘Preferred Values’ of resistor, each having a tolerance range of +/-10% covers all values from 10Ω to 100Ω. 2.2.1 shows how these tolerance ranges are used in the E12 series of resistors to cover (almost) all possible values of resistance between 10Ω and 100Ω. ![]() If a resistor of exactly 100KΩ is needed (an unusual situation) a resistor with the exact value can be selected from within this range or (more likely) a resistor with a closer tolerance can be used. ![]() Therefore there is no need to manufacture resistors with values between these upper and lower limits. Overlapping TolerancesĪ 100KΩ resistor having a +/-10% tolerance might be any value between 90KΩ and 110KΩ. Instead Resistors are made in a restricted range of values and each value is quoted as a specific number of ohms plus or minus a percentage of the quoted value, this range of possible values is called the tolerance of the resistor. To manufacture resistors of every possible value would be impractical.
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