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Resistor

Source: Wikipedia [1]

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Resistor marking

Most axial resistors use a pattern of colored stripes to indicate resistance. Surface-mount resistors are marked numerically, if they are big enough to permit marking; more-recent small sizes are impractical to mark. Cases are usually tan, brown, blue, or green, though other colors are occasionally found such as dark red or dark gray.

Early 20th century resistors, essentially uninsulated, were dipped in paint to cover their entire body for color coding. A second color of paint was applied to one end of the element, and a color dot (or band) in the middle provided the third digit. The rule was "body, tip, dot", providing two significant digits for value and the decimal multiplier, in that sequence. Default tolerance was ±20%. Closer-tolerance resistors had silver (±10%) or gold-colored (±5%) paint on the other end.

Four-band resistors

Four-band identification is the most commonly used color-coding scheme on resistors. It consists of four colored bands that are painted around the body of the resistor. The first two bands encode the first two significant digits of the resistance value, the third is a power-of-ten multiplier or number-of-zeroes, and the fourth is the tolerance accuracy, or acceptable error, of the value. The first three bands are equally spaced along the resistor; the spacing to the fourth band is wider. Sometimes a fifth band identifies the thermal coefficient, but this must be distinguished from the true 5-color system, with 3 significant digits.

For example, green-blue-yellow-red is 56×10⁴ Ω = 560 kΩ ± 2%. An easier description can be as followed: the first band, green, has a value of 5 and the second band, blue, has a value of 6, and is counted as 56. The third band, yellow, has a value of 10⁴, which adds four 0's to the end, creating 560,000Ω at ±2% tolerance accuracy. 560,000Ω changes to 560 kΩ ±2% (as a kilo- is 10³).

Each color corresponds to a certain digit, progressing from darker to lighter colors, as shown in the chart below.

Color	1st band	2nd band	3rd band (multiplier)	4th band (tolerance)	Temp. Coefficient
Black	0	0	×100
Brown	1	1	×101	±1% (F)	100 ppm
Red	2	2	×102	±2% (G)	50 ppm
Orange	3	3	×103		15 ppm
Yellow	4	4	×104		25 ppm
Green	5	5	×105	±0.5% (D)
Blue	6	6	×106	±0.25% (C)
Violet	7	7	×107	±0.1% (B)
Gray	8	8	×108	±0.05% (A)
White	9	9	×109
Gold			×10−1	±5% (J)
Silver			×10−2	±10% (K)
None				±20% (M)

There are many mnemonics for remembering these colors.

Preferred values

Early resistors were made in more or less arbitrary round numbers; a series might have 100, 125, 150, 200, 300, etc. Resistors as manufactured are subject to a certain percentage tolerance, and it makes sense to manufacture values that correlate with the tolerance, so that the actual value of a resistor overlaps slightly with its neighbors. Wider spacing leaves gaps; narrower spacing increases manufacturing and inventory costs to provide resistors that are more or less interchangeable.

A logical scheme is to produce resistors in a range of values which increase in a geometrical progression, so that each value is greater than its predecessor by a fixed multiplier or percentage, chosen to match the tolerance of the range. For example, for a tolerance of ±20% it makes sense to have each resistor about 1.5 times its predecessor, covering a decade in 6 values. In practice the factor used is 1.4678, giving values of 1.47, 2.15, 3.16, 4.64, 6.81, 10 for the 1-10 decade (a decade is a range increasing by a factor of 10; 0.1-1 and 10-100 are other examples); these are rounded in practice to 1.5, 2.2, 3.3, 4.7, 6.8, 10; followed, of course by 15, 22, 33, … and preceded by … 0.47, 0.68, 1. This scheme has been adopted as the E6 range of the IEC 60063 preferred number series. There are also E12, E24, E48, E96 and E192 ranges for components of ever tighter tolerance, with 12, 24, 96, and 192 different values within each decade. The actual values used are in the IEC 60063 lists of preferred numbers.

A resistor of 100 ohms ±20% would be expected to have a value between 80 and 120 ohms; its E6 neighbors are 68 (54-82) and 150 (120-180) ohms. A sensible spacing, E6 is used for ±20% components; E12 for ±10%; E24 for ±5%; E48 for ±2%, E96 for ±1%; E192 for ±0.5% or better. Resistors are manufactured in values from a few milliohms to about a gigaohm in IEC60063 ranges appropriate for their tolerance.

Earlier power wirewound resistors, such as brown vitreous-enameled types, however, were made with a different system of preferred values, such as some of those mentioned in the first sentence of this section.

5-band axial resistors

5-band identification is used for higher precision (lower tolerance) resistors (1%, 0.5%, 0.25%, 0.1%), to specify a third significant digit. The first three bands represent the significant digits, the fourth is the multiplier, and the fifth is the tolerance. Five-band resistors with a gold or silver 4th band are sometimes encountered, generally on older or specialized resistors. The 4th band is the tolerance and the 5th the temperature coefficient.

SMT resistors

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This image shows four surface-mount resistors (the component at the upper left is a capacitor) including two zero-ohm resistors. Zero-ohm links are often used instead of wire links, so that they can be inserted by a resistor-inserting machine. Of course, their resistance is finite, although quite low. Zero is simply a brief description of their function.

Surface mounted resistors are printed with numerical values in a code related to that used on axial resistors. Standard-tolerance surface-mount technology (SMT) resistors are marked with a three-digit code, in which the first two digits are the first two significant digits of the value and the third digit is the power of ten (the number of zeroes). For example:

334	= 33 × 10,000 ohms = 330 kilohms
222	= 22 × 100 ohms = 2.2 kilohms
473	= 47 × 1,000 ohms = 47 kilohms
105	= 10 × 100,000 ohms = 1.0 megohm

Resistances less than 100 ohms are written: 100, 220, 470. The final zero represents ten to the power zero, which is 1. For example:

100	= 10 × 1 ohm = 10 ohms
220	= 22 × 1 ohm = 22 ohms

Sometimes these values are marked as 10 or 22 to prevent a mistake.

Resistances less than 10 ohms have 'R' to indicate the position of the decimal point (radix point). For example:

4R7	= 4.7 ohms
0R22	= 0.22 ohms
0R01	= 0.01 ohms

Precision resistors are marked with a four-digit code, in which the first three digits are the significant figures and the fourth is the power of ten. For example:

1001	= 100 × 10 ohms = 1.00 kilohm
4992	= 499 × 100 ohms = 49.9 kilohm
1000	= 100 × 1 ohm = 100 ohms

000 and 0000 sometimes appear as values on surface-mount zero-ohm links, since these have (approximately) zero resistance.

More recent surface-mount resistors are too small, physically, to permit practical markings to be applied.

Industrial type designation

Format: [two letters]<space>[resistance value (three digit)]<nospace>[tolerance code(numerical - one digit)] <ref>Electronics and Communications Simplified by A. K. Maini, 9^thEd., Khanna Publications (India)</ref>

Power Rating at 70 °C

Type No.	Power rating (watts)	MIL-R-11 Style	MIL-R-39008 Style
BB	⅛	RC05	RCR05
CB	¼	RC07	RCR07
EB	½	RC20	RCR20
GB	1	RC32	RCR32
HB	2	RC42	RCR42
GM	3	-	-
HM	4	-	-

Tolerance Code

Industrial type designation	Tolerance	MIL Designation
5	±5%	J
2	±20%	M
1	±10%	K
-	±2%	G
-	±1%	F
-	±0.5%	D
-	±0.25%	C
-	±0.1%	B

The operational temperature range distinguishes commercial grade, industrial grade and military grade components.

• Commercial grade: 0 °C to 70 °C
• Industrial grade: −40 °C to 85 °C (sometimes −25 °C to 85 °C)
• Military grade: −55 °C to 125 °C (sometimes -65 °C to 275 °C)
• Standard Grade -5 °C to 60 °C

Inductor

Wikia article GFDL [2]

Inductors can be labeled with a number of different ways. The most common are text codes and color codes.

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Text Marking

• Values are in micro Henries (μH)
• First two digits are the value
• Third digit is the multiplier
• If there is an R, its acts as a decimal point, and there is no multiplier
• Examples:
  • 101 = 10*10¹μH = 100μH
  • 4R7 = 4.7μH

• Suffix
  • Sometimes the precision of the inductor will be marked, using a final letter F, G, J, K, or M
    • F = +/-1%
    • G = +/-2%
    • J = +/-5%
    • K = +/-10%
    • M = +/-20%

Color Code Markings

Inductors can be marked by colored bands or colored dots. Each color represents a value.

bands may be spaced evenly of have a gap between bands C and D

Band A	Band B	Band C	Band D
1st Digit	2nd Digit	Multiplier	Tolerance
		Silver 10-2 (0.01uH)	Gold 5%
		Gold 10-1 (0.1uH)	Silver 10%
	Black 0	Black 100 (1uH)	Black 20%
Brown 1	Brown 1	Brown 101 (10uH)
Red 2	Red 2	Red 102 (100uH)
Orange 3	Orange 3	Orange 103 (1000uH)
Yellow 4	Yellow 4	Yellow 104 (10000uH)
Green 5	Green 5
Blue 6	Blue 6
Violet 7	Violet 7
Gray 8	Gray 8
White 9	White 9

note: brown and violet can look very similar on some components. Violet and white can also look similar sometimes

Example

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• Band colors:
  • 1st band: yellow=4
  • 2nd band: violet=7
  • 3rd band: black=10^0=1
• Inductor value = 47x10^0uH = 47uH
  • 3rd band: silver = 10% tolerance

Zener Diodes

Markings on a circuit board

• Zener diode symbol.svg
• Zener diode symbol-2.svg

Any diode	Specificly zener diode
D	ZD
CR

Images

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Labeling on the diode

Part number labeled	Value Labeled
Label Full part number 52 33 A 1N5233A 1N 47 51 1N4751	Label Voltage 6.2 6.2V 6•2 6.2V 47 47V

References

Inductor:

• Inductor color codes
• Transformer color codes
• Component codes
• Inductor history: includes color codes dot and striped

Zener: