chapter  9
9 Pages

Other waveforms

A wave with a large mark-to-space ratio will thus have an average value nearly equal to its positive peak value, while a wave with a small markto-space ratio will have an average value nearly equal to its negative peak value (in the example shown in Figure 9.1, almost zero). Varying the markto-space ratio of a rectangular wave of voltage is often used as a method of d.c. motor speed control because, using electronic methods, this is simpler than varying the amplitude and much less likely to allow the motor to stall.

Figure 9.1 Rectangular waveforms or pulses showing mark and space and average values