Introduction to SMD Resistor Markings
Firstly, it’s important to note that chip resistors in the 0402 package lack any marking. For SMD resistors of other sizes, the marking process differs and is described below.
Marking of SMD Resistors with 2%, 5%, or 10% Tolerance
SMD resistors with a tolerance of 2%, 5%, or 10% are marked with three digits: the first two digits denote the mantissa, and the third digit represents the power of ten. Thus, the resistance value of the resistor is derived.
For example, a resistor marked as 452 means the first two digits ’45’ form the mantissa, and ‘2’ is the power, resulting in 45 * 10² = 4.5 kΩ.
Understanding the ‘R’ Marking
The Latin letter ‘R’ may also be used in resistor markings to indicate a decimal point, serving as an additional multiplier.
Marking of 1% Tolerance SMD Resistors Larger than 0805
For SMD resistors larger than 0805 with 1% tolerance, a four-digit code is used: the first three digits represent the mantissa, and the fourth digit is the power of ten. This code might also include the letter ‘R’ to signify a decimal point.
For instance, a resistor marked as 4501 means ‘450’ is the mantissa, and ‘1’ is the power, resulting in 450 * 10 = 4.5 kΩ.
Marking of 1% Tolerance SMD Resistors in 0603 Package
For 1% tolerance SMD resistors in the 0603 package, the marking is done using a combination of two digits and a letter, based on a specific table. The digit combination helps select the mantissa from the table, and the letter indicates the power of ten.
For example, a resistor marked as 14R means the first two digits ’14’ are a code from the table corresponding to 137, and ‘R’ represents ten to the power of one, resulting in 137 * 10 = 13.7 Ω.
Color Coding of Resistors
Learn about resistor color coding through this video:
