How to mark and how to use commonly used resistors
Direct Marking Method
The main parameters of the component are directly printed on the surface of the component. This method is mainly used for resistors with relatively high power ratings. For example, if the resistor surface is printed with "RXYC-50-T-1k5-±10%", it means a moisture-resistant, glazed, wire-wound, adjustable resistor with a rated power of 50W, a resistance value of 1.5kΩ, and an allowable error of ±10%.
Letter Symbol Method
As electronic components continue to miniaturize, especially with advancements in the manufacturing processes of surface-mounted components (SMCs and SMDs), the volume of resistors has become increasingly smaller, necessitating corresponding reforms in the textual symbols used on their surfaces. Generally, only three digits are used to indicate the value of the resistor, and the precision level is no longer explicitly indicated (typically less than ±5%). The specific rules are as follows:
(1) The resistor is indicated by a black coating on the component surface.
(2) The basic unit of measurement for resistors is the ohm (Ω), and the value is indicated using three digits.
(3) For resistors above ten times the basic unit, the first two digits represent the significant digits of the value, and the third digit indicates the multiplier. For example, "100" indicates a resistance value of 10×100 = 10Ω; "223" indicates a resistance value of 22×10^3 = 22kΩ.
(4) For components below ten times the basic unit, the first and third digits represent the significant digits of the value, and the second digit is replaced by the letter "R" to indicate the decimal point. For example, "3R9" indicates a resistance value of 3.9Ω.
