REFERENCE DATA
Much reference data has been given in the diagrams, tables, charts and text of preceding chapters. That given here is confined to information which is common to more than one section of the book.
RESISTORS
The colour coding system for resistors includes information on value, tolerance and grade. These characteristics are indicated by three or more coloured rings or dots which are read from the end of the resistor body towards its centre – Fig. 24.1. The first colour indicates the first digit of the value (refer to Table 24.1); the second colour gives the second digit of the value; and the third colour gives the number by which the first two figures should be multiplied to obtain the value of the resistor in ohms. The fourth colour, if present, indicates the manufacturing tolerance: typical tolerance figures encountered are ±1%, ±2%, ±5%, ±10% and ±20%. Where no tolerance is indicated it may be assumed that the tolerance is ±20%.
Grade 1 high-stability resistors are distinguished by a fifth band of salmon pink, or a body of that colour. For example, a resistor with four colour bands, the end one of yellow, the next violet, followed by orange and gold, would have a value of 47 kΩ with a tolerance of ±5%. Here the body colour would have no significance unless it were salmon pink to indicate a high stability type.
For surface-mounting colour codes, see under ‘capacitors’ below.