Read Axial Lead Resistors
Resistors are devices used in electronic circuits to provide a known resistance to the flow of electrical current. They are used to scale and limit the signal that is passing through them to help achieve the desired performance of the circuit. Since they are small and cylindrical, it would be difficult to print the resistance in a readable form on the cylindrical body. Instead, they are commonly marked with colored bands to indicate their resistive value. The bands are rings around the body of the device that when read will allow you to determine if the resistor value is correct for the desired limit of the electrical signal. Use these tips to learn how to read resistors.
Steps
- Position the resistor with the gold or silver color band to the right..
- Read the color sequence that must be decoded to determine resistance. Read the bands from left to right. The colors seen could be any of the following: black, brown, red, orange, yellow, green, blue, violet, gray and white.
- Determine the coded number for the resistive value. Change the colors to numbers as follows.
- Change black to 0.
- Change brown to 1.
- Change red to 2.
- Change orange to 3.
- Change yellow to 4.
- Change green to 5.
- Change blue to 6.
- Change violet to 7.
- Change gray to 8.
- Change white to 9.Remember this order with this mnemonic:
BLACK Birds Run On Your Garden, BLOOming Vegetables Grow Wonderfully
=
Black Brown Red Orange Yellow Green Blue Violet Gray White.
- Determine the tolerance of the resistor. Read the color of the right-most band. A gold band indicates that the actual resistance of the resistor will be within 5 percent of the value indicated by the coding. A silver band indicates that the actual resistance of the resistor will be within 10 percent of the number indicated by the coding. These values are important to calculate the variations that will occur from circuit to circuit randomly as more parts of the circuit are built.
- Determine the decoded number for the resistive value. You should have a three digit number derived from the color bands. (Your resistor might have four bands in addition to the tolerance band, in this case just write down all four numbers.)
- Change the last digit of the coded number to a number of zeros that are to be added to a base value indicated by the preceding numbers. For example, a coded number of 623 would require the addition of 3 zeros to the base value of 62, making the number 62000. If the third band had indicated that 0 zeros are to be added (a coded number of 620), then the number would become 62.
Tips
- The perception of color varies from person to person. If possible, compare a variety of resistors to more easily recognize the colors described.
- Only big resistors will have the color bands on one end. So position the resistor such that the gold or silver band is to the right. Then read from left to right.
