CHAPTER 5 ■ NUMBERS AND UNITSTolerance refers to how far away the part may be from the specified value. A 5% (gold) tolerance on a
1000 value part means it could be as low as 950 and as high as 1050. A particular piece could be exactly 1000,
but the manufacturer simply doesn’t guarantee it.
There can be five or even six bands on some fancier parts. The additional bands can represent
reliability, additional significant digits, or the amount of change with temperature. Most hobbyists are
unlikely to encounter or need such parts.
Determining Component Values with a Multimeter
If a marking or color band doesn’t immediately describe a value to you, there’s no reason to waste time
guessing or looking it up in a table. Simply connect the part to your multimeter! (Instructions on testing
specific parts appear throughout coming chapters.)
Another reason for checking a part with a multimeter is that few parts match the printed value. In fact,
a 10 mF capacitor could legitimately be 8 mF or even 18 mF (see Figure 5-9). Fortunately, most circuits tolerate
a wide range.
Figure 5-8. Turn the cardboard wheels to calculate color codes
Table 5-5. Color Tolerance Bands
Color Tolerance
(none) 20%
Silver 10%
Gold 5%
Red 2%
Brown 1%
Although the calculator will remain useful for odd values, it turns out there are only a few popular
values that you’ll use on a regular basis. You’ll quickly memorize these patterns: brown-black
(10 something), red-red (22 something), and yellow-violet (47 something).
If the part has four color bands, the last indicates the tolerance (see Table 5-5).