Appendix A.

Standard Values for Electronic Components.

Resistors, capacitors, some lines of RF chokes, and zener diodes come in standard values. The numbers may seem rather strange but they are based on a geometric series which will be explained later.

There are sets of values for tolerances of plus or minus 5%, 10% and 20%. The table below gives the standard values for the decade between 10 and 91. A value an any other decade can be obtained simply by multiplying a number from the table by the appropriate power of 10.

5%	10%	20%
10	10	10
11	NV	NV
12	12	NV
13	NV	NV
15	15	15
16	NV	NV
18	18	NV
20	NV	NV
22	22	22
24	NV	NV
27	27	NV
30	NV	NV
33	33	33
36	NV	NV
39	39	NV
43	NV	NV
47	47	47
51	NV	NV
56	56	NV
62	NV	NV
68	68	68
75	NV	NV
82	82	NV
91	NV	NV

Note, NV = No Value for this tolerance.

Why these strange values?

Let's take a 10 ohm 10% resistor as an example. That resistor could have any value between 9 and 11 ohms. It wouldn't make any sense to have an 11 ohm 10% resistor. That resistor could be anything between 9.9 and 12.1 ohms. The next higher 10% value is 12 ohms which may be anything between 10.8 and 13.2 ohms. True, there is a slight overlap but resistor values only have 2 significant digits and the next step up, 13 ohms would leave a substantial gap. The values are stepped so the tolerances just touch or overlap

1/4 watt 5% resistors are manufactured in values from 1 ohm to 10 Meg ohms

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