ELECTRIC SIGNALS
Electric Quantities used to represent, manipulate, transmit and store information.
DC Signal
DC stands for Direct Current.
The most basic signal type is a signal whose value is designed to remain constant with time.
xS = XS
Where XS represents the constant value of signal which may be positive, negative or zero.
Representation: VS
Upper case quantity with upper case subscript.
Graphical Representation
Frequency
Frequency for DC current is ZERO.
As
f=1/T
for DC current T= Infinite.
Any number divided by infinity is ZERO.
AC Signal
Also known as analog signalS
Alternating current (AC) is an electric current which periodically reverses direction, in contrast to direct current (DC) which flows only in one direction.
Representation:
Lower case letter with upper case subscripts.
e.g: vS , iS
Graphical Representation:
The usual waveform of alternating current in most electric power circuits is a sine wave , whose positive half-period corresponds with positive direction of the current and vice versa but AC signals can be also in the following forms.
The signal alternates sinusoidolly between extremes +Xm ans –Xm . The quantity Xm is called amplitude or peak value.
Xpk = Xm
Peak To Peak:
The difference between extremes is called peak to peak value.
Xpk-pk = 2Xpk = 2Xm
Root Mean Square Value:
The energetic value of signal is represented in the form of root mean square value and denoted as Xrms .
Frequency:
f=1/T
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