Oscilloscope

An oscilloscope is a measurement and testing instrument thet measures AC waveforms with two-axis on screen :

1. Vertical Axis

Represent the voltage.

2. Horizontal Axis

Represent the time or phase angle.

The quantities can be shown on the screen of an oscilloscope :

1. Amplitude ( Peak value, Vp).

2. Peak-to-peak value (Vpp).

3. Period (T) and frequency (f).

Example :

From figure as shown below, shows a AC sine wave displayed on the screen of an oscilloscope. The voltage knob is set at 5 v/div. Calculate the Peak-to-peak value (Vpp).

Solution :

Givev:

The variable value (v/div) = 5v/div

The number of vertical division = 6.4 division.

Therefore, peak-to peak value (Vpp) :

Vpp

= 5v/div X 6.4div

= 32V

Vp = Vpp/2 

      =16V

Average Value & Root Mean Square

Average Value( mean value )

The mean or average value for a complete AC sine wave is zero because of the symmetrical shape of the sine wave.

Positive value = Negative value

Root Mean Square( rms )

The rms is the effective voltage that can generate the same amount of power as a direct current ( DC) that flows through the resistor.

Vrms = (1/√2)X Vp

         = 0.707 X Vp

Frequency, f & Period, T - AC

Frequency, f & Period, T - AC

Example :

From the waferorm shown above :

a) Frequency, f = 2Hz

b) Period, T = 1/f

                       1/2

                        0.5 s (time for one cycle)

Peak value ( Amplitude) Vp :

The maximum current/voltage that can be achieved by an AC sine waveform from zero at vertical axis.

Peak-to-peak value Vpp :

That is measured from the maximum positive voltage to the maximum negative voltage ( or twice its peak value).

Example :

Peak value, Vp = 3V

Peak-to-peak value, Vpp = 3 - (-3) = 6V @

                                Vpp = 2Vp

                                        = 2 X 3V

                                        = 6V

Alternating Current Circuits - (AC)

The Differences Between (AC) & (DC)

a) Direct Current- DC

1. DC is the flow of current in one direction.

2. To generate DC, cell or battery is used.

b) Alternating Current- AC

1. AC is a type of current thet changes its direction constantly according to time.

2. Sine wave as shown below is normally used in power supply.

3. Other AC Waveforms.