How To Compute Resistance Value Resistor, as its name implies, resists the flow of electrons in the circuits. And it specify with circuit symbol “R” on various motherboard. . Resistance measurement unit is Ohm Ω. There are two types of resistors; fixed resistors and Variable resistors or potentiometers. We mainly deal with SMD or fixed resistors. Fixed Resistors: The resistors are made with different shapes and sizes. And the only differences between them are on their resistance, for manufacturers one or two parameter specified, such as: A) Nominal value B) Tolerance (% error) The Nominal value should be ideal one. But to reduce production cost, resistors are produced with variable tolerances in other word with different percentages of errors. In fact, there is no perfect resistor. Most of the resistors which you see are with black, green and blue colors on laptop motherboards. Below is explanation about how to study resistors. a) Character code and numeral code write the first and second digit and add zero to third digit number, for example ; if the third digit is three so, add three zero instead of third digit. Thus, the resistor value is computed by ohm. b) Two numerals and one letter ratio character ohm R Kilo ohm K Mega ohm M As you see on the table, resistorratio and the place of decimal point character are along with two numerals, these are specifying the numerals of resistors. Here also, the percentage error of resistor is not clear. Specify the Nominal value of below resistors. c) Two numerals and two characters First character and two numerals are resistor value and second character is such as on the below table is tolerance value of the resistor. Here is a sample of nominal and tolerance possibility values are computed which used above table, so see below instances: First character= ratio second character= tolerance
