Reading SMD resistor codes, particularly 4-digit markings, requires understanding the specific system used. According to the provided reference, the presence of a fourth digit indicates information about the component's tolerance.
SMD resistors are marked with numerical codes to indicate their resistance value and sometimes tolerance. Common systems include 3-digit, 4-digit, and EIA-96 markings. The reference outlines a system based on the number of digits present.
The 3-Digit System
In the 3-digit system described in the reference:
- The first two digits represent the significant figures of the resistance value.
- The third digit is the multiplier, indicating the number of zeros you need to add after the significant figures.
Example (from reference):
If the code on the resistor reads ``473'':
- The first two digits are
47(significant figures). - The third digit is
3(multiplier, add 3 zeros). - The value is 47 followed by three zeros: 47,000 ohms (Ω).
- 47,000 Ω is equivalent to 47 kilohms (kΩ).
The reference also states that for the example code ``473'', this translates to a 5% tolerance, implying a standard tolerance level for this type of marking.
The 4-Digit System (According to Reference)
According to the provided reference, when a fourth digit is present in the marking:
- The fourth digit represents the tolerance.
The reference explicitly states: "If there is a fourth digit, it represents the tolerance."
Note on Reference Detail:
Based strictly on the provided reference, the system for interpreting the first three digits when a fourth digit is present is not detailed. The focus of the reference is on what the fourth digit signifies in contrast to the 3-digit system – specifically, that it provides tolerance information. The reference does not explain how a specific digit value (like '1', '5', etc.) maps to a percentage tolerance (like 1%, 5%).
Therefore, according to the specific information provided, a 4-digit code tells you that the final digit is related to the tolerance of the resistor, differentiating it from a standard 3-digit code where tolerance might be implied or marked separately.
Summary Comparison
Based on the information from the reference:
| Feature | 3-Digit Code | 4-Digit Code (as per reference) |
|---|---|---|
| Digits 1 & 2 | Significant Figures | Role not detailed in reference |
| Digit 3 | Multiplier (Zeros) | Role not detailed in reference |
| Digit 4 | Not Present | Represents Tolerance |
| Example (from ref) | 473 = 47kΩ |
No 4-digit example provided |
| Tolerance (from ref example) | 5% | Represented by the 4th digit |
Reference Used:
- The first two digits represent the significant figures, while the third digit indicates the number of zeros to add. If there is a fourth digit, it represents the tolerance. For example, if the code on the resistor reads ``473'', this translates to a 47k-ohm resistor with a 5% tolerance.02-Apr-2024
