SMD resistance which means surface mounted technology resistors is resistance in microchips that are mounted on a circuit board. Is quite different from the ordinary resistors which have their color codes on their body for identifications. Instead, SMD resistors have their value written on their body. These figures on their body are used in calculating values of SMD resistor. This blog post details the process on how to calculate the value SMD resistor.
The SMD resistors are dominating the other type of resistor as industry and new technologies are now going for SMD due to the less space it occupied in a circuit, especially building complex circuits.
This article will help in calculating the value of the values of SMD.
How to calculate SMD resistors code.
To calculate a value SMD resistor, the first thing to do is to check the number of digits written on them. To know if it is 3 digits or 4 digits.
Calculating the value of 3 digits SMD resistor code.
3 digits SMD resistors are the ones that have 3 different values of number or alphabet written on them.
These are ways to determine the values of the resistor.
- the first two digits on the resistor indicate the significant value of the resistor. The first 2 values are called together as it is. For example, 223 SMD resistor, 22 is the first 2 digits and means 22 (twenty-two).
- The third digit which is the last digit is the multiplier, i.e the first two values are multiply by the third digits. The last digit which is the multiplier is in the power of ten. i.e 10^. If the last digit happens to be 0 it means the two values multiple by 10^0. For example, 223 SMD resistor means 22×10^3 = 22000 ohms or 22k ohms.
- In situations where the alphabet number like ‘R’ appears in between the first digit. Like 2R2. The alphabetical value is used to indicate a decimal place. Anywhere you see the ‘R’ it means a decimal place. For instance, 2R2 means 2.2 and 1R2 means 1.2, and vise vasa. So 2R2 SMD resistor simply means 2.2 ohms or 2.2k And R23 simply means 0.2×10^3= 200 ohms.
- All the SMD resistor that is below 10 values don’t have a multiplier meaning they are to be in 2digits values.
Calculating the value of a 4 digits SMD resistor code.
No much difference exists between the way we read the 3 digits values to the way 4 digits are calculated. The only change here is that the first third value will be the significant value why the fourth one is the multiplier.
- The first three digits of the SMD resistor is the significant number.
- The last digit which is the fourth digit is the multiplier to power ten. All the last or fourth digit is ten power by the digit multiply with the first third digit. For instance, in 2230 SMD resistor, is equal to 223×10^0= 22 ohms. From the examples we see that the last digit is 0, so we multiply ten power zero to the first three digits.
- When R is used before or in between the digits, during the calculation substitute it with a decimal dot. For instance, R235 is 0.23×10^5= 23000 ohms or 23k ohms. And 23R3 =23.×10^3= 23000 ohms or 23k ohms.
- Any SMD resistor that is below 10 ohms does not have a multiplier.
Calculating for EIA-96 SMD resistor code.
This is the new method of marking SMD resistors. About 1% of SMD resistors use the EIA-96 coding system. It normally comes in three digits, the first two digits are used to determine the three significant numbers of the resistor value, while the third digit which is the alphabet indicates the multiplier.
Below are the table of values of EIA-96 SMD resistor from 1-96 and their multiplier. The table provide assistance in calculating the value of SMD resistor.
Calculating EIA-96 SMD resistor codes and values.
Multiplier for EIA-96 SMD table for calculating resistor value.
|Y OR R||0.01|
|X Or S||0.1|
|B OR H||10|
The above table 2 is the multiplier table that shows the multiplier of the corresponding alphabet.
23Y =23×0.01 = 0.23 ohms.
23D is equal to 23×1000= 23k ohms.
While table 1 is for the EIA SMD resistors without an alphabet.