Periodic signals are more commonly identified by their frequency (usually abbreviated as f ), rather than their period. The frequency of a signal is the inverse of the period. Mathematically, this means that:
The frequency of a signal tells us how many times the signal repeats itself during one second. Units of frequency are in cycles per second, or Hertz (abbreviated as Hz). Therefore, a signal with a frequency of 100Hz goes through 100 cycles (periods) in one second—the period of the signal is 0.01 seconds. Higher frequency signals change more rapidly, and have shorter periods than lower frequency signals.
Although any repetitious signal is periodic, there are a few specific signals which are very commonly used in the analysis and testing of electrical circuits. Three examples of common voltage signals are shown in Fig. 2. Periodic voltages are typically classified according to:
The voltage signals in Fig. 2 all have zero average values—they are vertically “centered” around zero volts. We can shift all of these signals vertically by adding a constant value to the time-varying signal—this constant value is called an offset. Most waveform generators provide the ability to add an offset to a basic time-varying signal.