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All SM resistors conform to a 3-digit or 4-digit code. But
there are a number of codes, according to the tolerance of the resistor. It's
getting very complicated.
Here is a basic 3-digit SM resistor:
A 330k SM resistor
The first two digits represent the two digits in the answer. The third digit
represents the number of zero's you must place after the two digits. The answer
will be OHMS. For example: 334 is written 33 0 000. This is written 330,000
ohms. The
comma can be replaced by the letter "k". The final answer is: 330k.
222 = 22 00 = 2,200 = 2k2
473 = 47 000 = 47,000 = 47k
105 = 10 00000 = 1,000,000 = 1M = one million ohms
There is one trick you have to remember. Resistances less than 100 ohms are
written: 100, 220, 470. These are 10 and NO zero's = 10 ohms = 10R
or 22 and no zero's = 22R or 47 and no zero's = 47R. Sometimes the
resistor is marked: 10, 22 and 47 to prevent a mistake.
Remember:
R = ohms
k = kilo ohms = 1,000 ohms
M = Meg = 1,000,000 ohms
The 3 letters (R, k and M) are put in place of the decimal point. This way you
cannot make a mistake when reading a value of resistance.
THE COMPLETE RANGE OF SM
RESISTOR
MARKINGS
Click to see the complete range of SM resistor markings for 3-digit code:
Click to see the complete range of SM resistor markings for 4-digit code:
0000 is a value on a surface-mount
resistor. It is a zero-ohm LINK!
Resistances less than 10 ohms have 'R' to indicate the
position of the decimal point.
Here are some examples:
|
Three Digit
Examples
|
Four Digit
Examples
|
|
330
is 33 ohms - not
330 ohms |
1000
is 100 ohms
- not 1000 ohms
|
|
221 is
220 ohms |
4992
is 49 900 ohms, or 49k9
|
|
683 is
68 000 ohms, or 68k |
1623
is 162 000 ohms, or 162k
|
|
105 is
1 000 000 ohms, or 1M |
0R56
or R56 is
0.56 ohms
|
|
8R2
is 8.2 ohms |
|
A new coding system has appeared on 1% types.
This is known as the EIA-96 marking method. It consists of a
three-character code. The first two digits signify the 3
significant digits of the resistor value, using the lookup
table below. The third character - a letter - signifies the
multiplier.
|
code
|
value
|
|
code
|
value
|
|
code
|
value
|
|
code
|
value
|
|
code
|
value
|
|
code
|
value
|
|
01
|
100
|
17
|
147
|
33
|
215
|
49
|
316
|
65
|
464
|
81
|
681
|
|
02
|
102
|
18
|
150
|
34
|
221
|
50
|
324
|
66
|
475
|
82
|
698
|
|
03
|
105
|
19
|
154
|
35
|
226
|
51
|
332
|
67
|
487
|
83
|
715
|
|
04
|
107
|
20
|
158
|
36
|
232
|
52
|
340
|
68
|
499
|
84
|
732
|
|
05
|
110
|
21
|
162
|
37
|
237
|
53
|
348
|
69
|
511
|
85
|
750
|
|
06
|
113
|
22
|
165
|
38
|
243
|
54
|
357
|
70
|
523
|
86
|
768
|
|
07
|
115
|
23
|
169
|
39
|
249
|
55
|
365
|
71
|
536
|
87
|
787
|
|
08
|
118
|
24
|
174
|
40
|
255
|
56
|
374
|
72
|
549
|
88
|
806
|
|
09
|
121
|
25
|
178
|
41
|
261
|
57
|
383
|
73
|
562
|
89
|
825
|
|
10
|
124
|
26
|
182
|
42
|
267
|
58
|
392
|
74
|
576
|
90
|
845
|
|
11
|
127
|
27
|
187
|
43
|
274
|
59
|
402
|
75
|
590
|
91
|
866
|
|
12
|
130
|
28
|
191
|
44
|
280
|
60
|
412
|
76
|
604
|
92
|
887
|
|
13
|
133
|
29
|
196
|
45
|
287
|
61
|
422
|
77
|
619
|
93
|
909
|
|
14
|
137
|
30
|
200
|
46
|
294
|
62
|
432
|
78
|
634
|
94
|
931
|
|
15
|
140
|
31
|
205
|
47
|
301
|
63
|
442
|
79
|
649
|
95
|
953
|
|
16
|
143
|
32
|
210
|
48
|
309
|
64
|
453
|
80
|
665
|
96
|
976
|
The multiplier letters
are as follows:
|
letter
|
mult
|
|
letter
|
mult
|
|
F
|
100000
|
B
|
10
|
|
E
|
10000
|
A
|
1
|
|
D
|
1000
|
X or S
|
0.1
|
|
C
|
100
|
Y or R
|
0.01
|
22A is a 165 ohm resistor, 68C
is a 49900 ohm (49k9) and 43E a 2740000 (2M74). This
marking scheme applies to 1% resistors only.
A similar arrangement can be used for 2%
and 5% tolerance types. The multiplier letters are
identical to 1% ones, but occur before the number
code and the following code is used:
|
2% |
|
5% |
|
code |
value
|
|
code |
value |
code
|
value
|
|
code |
value |
|
01 |
100
|
13 |
330
|
25
|
100
|
37
|
330
|
|
02 |
110
|
14 |
360
|
26
|
110
|
38
|
360
|
|
03 |
120
|
15 |
390
|
27
|
120
|
39
|
390
|
|
04 |
130
|
16 |
430
|
28
|
130
|
40
|
430
|
|
05 |
150
|
17 |
470
|
29
|
150
|
41
|
470
|
|
06 |
160
|
18 |
510
|
30
|
160
|
42
|
510
|
|
07 |
180
|
19 |
560
|
31
|
180
|
43
|
560
|
|
08 |
200
|
20 |
620
|
32
|
200
|
44
|
620
|
|
09 |
220
|
21 |
680
|
33
|
220
|
45
|
680
|
|
10 |
240
|
22 |
750
|
34
|
240
|
46
|
750
|
|
11 |
270
|
23 |
820
|
35
|
270
|
47
|
820
|
|
12 |
300
|
24 |
910
|
36
|
300
|
48
|
910
|
With this arrangement, C31
is 5%, 18000 ohm (18k), and D18 is 510000 ohms (510k) 2%
tolerance.
Always check with an ohm-meter (a multimeter) to make sure.
Chip resistors come in the
following styles and ratings:
Style:
0402, 0603, 0805, 1206, 1210, 2010, 2512, 3616, 4022
Power Rating:
0402(1/16W), 0603(1/10W), 0805(1/8W), 1206(1/4W), 1210(1/3W),
2010(3/4W), 2512(1W), 3616(2W), 4022(3W)
Tolerance: 0.1%,
0.5%, 1%, 5%
Temperature Coefficient:
25ppm 50ppm 100ppm
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