The 4-band code is used for marking low precision resistors with 5%, 10% and 20% tolerances. Identifying the value will become easy with a little practice, as there are only a few simple rules to remember:
- The first two bands represent the most significant digits of the resistance value. Colors are assigned to all the numbers between 0 and 9, and the color bands basically translate the numbers into a visible code. Black is 0, brown is 1, red is 2 and so on (see the color code table below). So, for example, if a resistor has brown and red as the first two bands, the most significant digits will be 1 and 2 (12).
- The third band indicates the multiplier telling you the power of ten to which the two significant digits must be multiplied (or how many zeros to add), using the same assigned value for each color as in the previous step. For example, if this band is red (2), you will multiply it by 102 = 100 (or add 2 zeros). So, for the resistor we used in the previous example, the value would be: 12 x 100 = 1200Ω (1.2kΩ).
Note: If the multiplier band is gold or silver, the decimal point is moved to the left by one or two places (divided by 10 or 100). - The tolerance band (the deviation from the specified value) is next, usually spaced away from the others, or it's a little bit wider. A color is assigned to each tolerance: gold is 5%, silver is 10%. 20% resistors have only 3 color bands - the tolerance band is missing.
So, for a 560 ohm, 5% resistor the color stripes will be green, blue, brown and gold. Green and blue are the first significant digits (56); brown is the multiplier (101 = 10) and gold is the tolerance (5%). 56 x 10 = 560Ω.
If the 3rd band would be red instead of brown, the multiplier would be (102 = 100) instead of 10 and the resistor value would be 56 x 100 = 5600 ohms = 5.6 k ohms.
If the multiplier band is gold or silver, then the decimal point is moved to the left one or two places (divided by 10 or 100). For example, a resistor with green, blue, silver and gold rings has a value of 56 x 0.01 = 0.56Ω.
The 5-band code
The 5 band code is used for marking high quality, precision resistors with 2%, 1% or lower tolerances. The rules are similar to the previous system; the only difference is the number of digit bands. The first 3 bands will represent the value, the 4th band will be the multiplier and the 5th stripe will give us the tolerance.
Optional band
A few resistors have an additional band - often giving beginners a bit of trouble - indicating either the reliability or the temperature coefficient.
The reliability band specifies the failure rate per 1000 hours (assuming that a full wattage being applied to the resistor). This stripe is found primarily on 4-band resistors made for military applications and seldom used in commercial electronics.
The temperature coefficient is more commonly marked, especially on quality 5-band resistors, as it starts to become an important factor for precision components. For a resistor with temperature coefficient of 200 ppm, for example, a change in temperature of 50°C causes a value change of 1%. The most common values for this band are presented in the color chart above. - Examples:
- Four band code:
Green, blue, red, with silver tolerance band: 56 x 100 = 5.6 kohms, with a tolerance of 10% 
Brown, black, orange, gold tolerance band: 10 x 1000 = 10000 ohms (or 10K ohms), with a tolerance of 5%
Red, red, brown, silver tolerance band: 22 x 10 = 220 ohms (220 ohms), with a tolerance of 10%
More 4 band resistor color code examples: E12 and E24 series.
Five band code:
Blue, brown, white, brown, red tolerance band: 619 x 10 = 6190 ohms (6.19K ohms), with a tolerance of 2%
Red, red, brown, black, with a brown tolerance band: 221 x 1 = 221 ohms, with a tolerance of 1%
Brown, black, black, red, with a brown tolerance band: 100 x 100 = 10000 ohms (10.0K), with a tolerance of 1%
Standard EIA Decade Resistor Values
Resistors are available in standard values such as 1K, 2.2K, 4.7K, and so on. The two most common standards are the E12 and E24. You will notice that in the E12 series each succeeding value falls within +/- 10% of the previous value. The E24 range includes all of the E12 values, plus a further 12 to enable the selection of more precise resistances.
The E6 (20%) range is a subset of the E12 (10%) range and the E12 range is a subset of the E24 (5%) range. Similarly, the E48 (2%) range is a subset of the E96 (1%) range and the E96 range is a subset of the E192 (0.5% or less) range. Note, that the E24 range is technically also a subset of the E48 range, however, because of the different number of digits used for representation and rounding errors, the corresponding values in the two series do not match.
E6 series: (20% tolerance)
10, 15, 22, 33, 47, 68
E12 series: (10% tolerance) - examples...
10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82
E24 series: (5% tolerance) - examples...
10, 11, 12, 13, 15, 16, 18, 20, 22, 24, 27, 30, 33, 36, 39, 43, 47, 51, 56, 62, 68, 75, 82, 91
E48 series: (2% tolerance) - examples...
100, 105, 110, 115, 121, 127, 133, 140, 147, 154, 162, 169, 178, 187, 196, 205, 215, 226, 237, 249, 261, 274, 287, 301, 316, 332, 348, 365, 383, 402, 422, 442, 464, 487, 511, 536, 562, 590, 619, 649, 681, 715, 750, 787, 825, 866, 909, 953
E96 series: (1% tolerance)
100, 102, 105, 107, 110, 113, 115, 118, 121, 124, 127, 130, 133, 137, 140, 143, 147, 150, 154, 158, 162, 165, 169, 174, 178, 182, 187, 191, 196, 200, 205, 210, 215, 221, 226, 232, 237, 243, 249, 255, 261, 267, 274, 280, 287, 294, 301, 309, 316, 324, 332, 340, 348, 357, 365, 374, 383, 392, 402, 412, 422, 432, 442, 453, 464, 475, 487, 491, 511, 523, 536, 549, 562, 576, 590, 604, 619, 634, 649, 665, 681, 698, 715, 732, 750, 768, 787, 806, 825, 845, 866, 887, 909, 931, 959, 976
Final thoughts
So, why all this trouble with color coding? The resistance value could be stamped or painted on the body of the through-hole resistor, no? Yes, but the numbers would be quite small and difficult to read. Also, the markings would easily rub off or become smeared with time.
Old, clear-marked resistors were less confusing for the beginners, but - for example - if such a resistor is mounted with the marked side down, you cannot read its value unless you take it out of the circuit.
The resistor color code might seem a bit confusing and rather inconvenient at first, but most electronics hobbyists and technicians are surprised when they realize how quickly they've memorized the color chart without the use of mnemonics or other silly shortcuts.
The color code is quite intuitive, and after a brief familiarization period, it's quite easy to use, it will become almost a second nature.
Postingan
Tidak ada komentar:
Posting Komentar