Angular measurement that specifies the position of a sine wave relative to a reference. To show that a sine wave is shifted to the left or right of this reference.

Example

Power relationships developed for dc circuits apply to ac circuits except you must use rms values in ac circuits when calculating power.

Power formulas

A sinusoidal waveform is the fundamental alternating current (ac) and alternating voltage waveform.

A sinusoidal waveform is the fundamental alternating current (ac) and alternating voltage waveform.

Effective value: The dc current that delivers the same average power to a resistor as the periodic current.

"Root Mean Square (RMS): DC current which when flowing through a circuit for a given time period produces the same heat as produced by the AC current flowing through the same circuit for the same time period"

The average value of a sine wave when taken over one complete cycle is always 0.

A pulse can be described as a very rapid transition (leading edge) from one voltage or current level (baseline) to another level; after an interval of time, a very rapid transition (trailing edge) back to the original baseline level. The transitions in level are called steps. An ideal pulse consists of two opposite-going steps of equal amplitude.

Rise time (tr) is the time required for the pulse to go from 10% of its amplitude to 90% of its amplitude.

Fall time (tf) is the time required for the pulse to go from 90% of its amplitude to 10% of its amplitude.

Pulse width is the time between the point on the leading edge where the value is 50% of the amplitude and the point on the trailing edge where the value is 50% of the amplitude.

Repetitive Pulses Any waveform that repeats itself at fixed intervals is periodic, The rate at which the pulses repeat is the pulse repetition frequency,

The duty cycle is the ratio of the pulse width (tW) to the period (T) and is usually expressed as a percentage.

Average Value of a Pulse Waveform

Subtopic

Negative going ramps

Positive going ramps

Triangular Waveforms: composed of positive-going and negative-going ramps having equal slopes. The period of this waveform can be measured from one peak to the next corresponding peak.

Sawtooth Waveforms: Consist of two ramps, one of much longer (positive-going ramp) duration than the other (negative-going ramp). A sawtooth waveform is used in automatic test equipment, control systems, and certain types of displays, including analog oscilloscopes.

Odd harmonics are frequencies that are odd multiples of the fundamental frequency. For example, a 3 kHz frequency in this case is the third harmonic.

Even harmonics are frequencies that are even multiples of the fundamental frequency. For example, the fourth harmonic is 800 Hz.

Composite Waveform: A non-sinusoidal wave is a composite of the fundamental and the harmonics. Some types of waveforms have only odd harmonics, some have only even harmonics, and some contain both.