Overview
Resistors are marked in various ways to indicate their resistance, tolerance, and type. Understanding these markings is crucial for correct circuit design, maintenance, and PCB layout inspection.
Resistor Color Bands
Color bands are most common on through-hole resistors. Each band represents a digit, multiplier, or tolerance value:
| Color | Digit | Multiplier | Tolerance |
|---|---|---|---|
| Black | 0 | ×1 | - |
| Brown | 1 | ×10 | ±1% |
| Red | 2 | ×100 | ±2% |
| Gold | - | ×0.1 | ±5% |
| Silver | - | ×0.01 | ±10% |
SMD Resistor Markings
Surface-mount resistors use numerical codes:
- 3-digit: First two digits = value, third = multiplier. Example: 103 = 10 × 10³ = 10 kΩ
- 4-digit: Higher precision. Example: 4701 = 470 × 10 = 4.7 kΩ
- EIA-96: Used for 1% tolerance with 2 digits + letter. Ex: 24C = 178Ω
IEC & ANSI Circuit Symbols
Resistors may appear on circuit diagrams with different symbols:
- IEC: Rectangle
- ANSI: Zigzag line
- Potentiometers are shown with an arrow across the resistor symbol.
Real-World Marking Examples
Here are some common resistor types and how they are marked:
- Carbon Film (through-hole): 5-band color codes
- SMD 0603: "102" means 1kΩ
- High-power resistor: Stamped with value and wattage, e.g., 5W 10Ω
Video Guide
Visual tutorial on identifying resistor codes and reading values:
Frequently Asked Questions
Q: How do I tell the resistor's orientation?
A: Look for a gap before the tolerance band (gold/silver); start from the other end.
Q: Are SMD resistor codes always standard?
A: Most follow EIA-96 or 3/4-digit systems, but check the datasheet if unsure.
Need Help Finding Resistors?
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Recommended Reading: Ultimate Guide to Resistors
