# SMD Resistor Code Identification Guide
## Introduction to SMD Resistors
Surface Mount Device (SMD) resistors are widely used in modern electronics due to their compact size and suitability for automated assembly processes. Unlike through-hole resistors with color bands, SMD resistors use a numeric code system to indicate their resistance value.
## Understanding the SMD Resistor Code System
SMD resistors typically use one of three coding systems:
### 1. Three-digit Code
The simplest system uses three digits where:
– First two digits represent significant figures
– Third digit represents the multiplier (number of zeros)
Example: “472” means 47 × 10² = 4700Ω or 4.7kΩ
### 2. Four-digit Code
For more precise values, a four-digit system is used:
– First three digits represent significant figures
– Fourth digit represents the multiplier
Example: “4702” means 470 × 10² = 47000Ω or 47kΩ
### 3. EIA-96 Code
For very small resistors, an alphanumeric code is used:
– First two digits represent a code from a table (01-96)
– Letter represents the multiplier
Example: “01A” means 100 × 10⁰ = 100Ω
## How to Read SMD Resistor Codes
Follow these steps to decode SMD resistor markings:
1. Determine which coding system is used (3-digit, 4-digit, or EIA-96)
2. Identify the significant figures based on the digits
3. Apply the multiplier indicated by the last digit or letter
4. The result is the resistance value in ohms
## Common SMD Resistor Code Examples
Here are some frequently encountered codes and their meanings:
| Code | Value | Explanation |
|---|---|---|
| 101 | 100Ω | 10 × 10¹ = 100Ω |
| 223 | 22kΩ | 22 × 10³ = 22000Ω |
| 4701 | 4.7kΩ | 470 × 10¹ = 4700Ω |
| 01C | 10kΩ | 100 × 10² = 10000Ω (EIA-96) |
## Special Cases and Additional Markings
Some SMD resistors may have additional markings:
R marking: The letter “R” is used to indicate a decimal point. Example: “4R7” means 4.7Ω
Zero-ohm resistors: Marked as “0” or “000” – used as jumpers on PCBs
Tolerance codes: Sometimes included as a letter after the numeric code (F=±1%, J=±5%, etc.)
## Tools for SMD Resistor Identification
Several tools can help with SMD resistor code identification:
- Digital multimeter for verification
- Magnifying glass or microscope for small components
- Online SMD resistor code calculators
- Mobile apps that decode resistor markings
