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SMD Resistor

Marking Value

    Enter a resistor’s value to get its marking or enter its marking to get a value. If over specified (both a value and marking are entered) the resistor’s value is used to find its marking. This solver deals with the most common styles of marking (three or four numbers with optional ‘R’ and two number plus letter). See the following discussion for additional details.

About SMT Resistor Marking

    Surface mount resistors are marked using different schemes. There are two commonly used methods. In the first, more common scheme, the resistor is marked with three or four numbers. These numbers correspond to three and four value band color codes used in through hole resistors (see the “Resistor Color Codes” solver for additional information”). For low value resistors, the letter “R” is used to denote the decimal points position.

    The second marking scheme (EIA-96) uses two digits followed by a letter. The two digit number is used to look up a value (there is no one to one correspondence between the digits and the value) and the letter is used to look up the multiplier.

    This solver accepts both marking style. Another marking scheme that uses two or three numbers in combination with one letter is also in use. In this case, the value can easily be read without the use of a decoder.

    In this style of marking, the value is read directly with the letter used as a stand in for the decimal place. The letter also lets you know the magnitude of the value. The letters used are R, K, M, and L. The following table gives a number of examples of how the values are read. Although the tolerance isn’t given as part of the marking, if there are two numbers used, the resistor has a 5% or 10% tolerance and if three numbers are used the tolerance is 1% or better.

Table of examples of surface mount resistor markings.

copyright © 2021 John Miskimins


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