An oscilloscope displays several types of waves, which can be classified into sine waves, square and rectangular waves, step and pulse shapes, sawtooth and triangle waves, synchronous and asynchronous signals, periodic and non-periodic signals, and complex waves.
The basic wave shape, sine wave features harmonious mathematical properties similar to the sine shape studied in trigonometry class. Test signals generated by the signal generator’s oscillator circuit are often sine waves. Many AC (alternating current) power sources also generate sine waves.
Another common type of wave shape, the square wave is basically a voltage that goes high and low (or turns on and off) at regular intervals. A standard wave for testing amplifiers, square waves are also used for timing signals in radio, television and computer circuitry.
Although not of equal length, rectangular wave also has high and low intervals comparable to that of square waves. This type of wave is specifically important when analyzing digital circuitry.
Step and pulse-shaped signals occurring non-periodically or rarely are referred to as transient or single-shot signals. A step shows a sudden change in voltage comparable to the change seen when turning on a power switch, while a pulse represents a sudden change in voltage comparable to the change observed when switching on and then off again a power. A group of pulse traveling together comprises a pulse train. Used by a computer’s digital components to communicate with each other, pulses are also featured in radar, x-ray and communications equipment.
Sawtooth and triangle waves are generated by circuits used to control voltages linearly. The transitions between the waves’ voltage levels change at a constant rate. These transitions are also known as ramps.
A synchronous signal exists when there is a timing relationship between two signals. A computer’s data, clock and address signals are some of the examples of synchronous signals. Meanwhile, asynchronous signals represent those signals with no timing relationship.
Repetitive signals are also called periodic signals, while non-periodic signals refer to those that constantly change.
Finally, a complex wave indicates a combination of the characteristics of sine, steps, squares and pulses. The signal information in this type of wave may be embedded in the form of amplitude, frequency variations and/or phase.
Some oscilloscopes can display specific kinds of complex waveforms in special ways. Telecommunications, for instance, can be displayed as a constellation diagram or as an eye pattern.
An oscilloscope can also display the signals of telecommunications digital data as a special type of waveform known as an eye pattern, attributed to its similarity to a series of eyes. Eye patterns is created when the receiver’s digital data is applied and sampled to the vertical input, while the data rate is utilized to trigger the horizontal sweep. The eye pattern displays a unit interval of data with all potential edge transitions and states superimposed in a single comprehensive view.
A constellation diagram represents a signal adjusted by a digital modulation scheme such as phase-shift keying or quadrature amplitude modulation.
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