Introduction1st semester 1434-1435

King Saud University College of Applied studies and Community Service1301CTBy: Nour Alhariqi

Outline

•Concepts and Definitions.•Laboratory Equipments.

Waves (Signals)

• Wave is a disturbance or oscillation that travels through space and matter, – sound waves, voltage waves, ..

•A waveform is a graphic representation of a wave. ▫A voltage waveform shows time on the horizontal axis

and voltage on the vertical axis•Some common waveforms:

▫Sine waves and damped sine waves. ▫Square and rectangular waves.▫Triangle and saw-tooth waves.

Sine Waves and Damped Sine Waves

•The sine wave  is a wave that has a smooth repetitive oscillation. 

•The damped sine wave is a special case that oscillates, but winds down over time

Square and Rectangular Waves

•A square wave is a wave that turns on and off (or goes high and low) at regular intervals.

•The rectangular wave is like the square wave except that the high and low time intervals are not of equal length.

Sawtooth and Triangle Waves

• In sawtooth and triangle waves the transitions between voltage levels change at a constant rate. These transitions are called ramps.

•a sawtooth wave ramps upward and then sharply drops.

•A triangle wave has symmetrical rising and falling ramps.

Analog and Digital SignalsAnalog signal Digital signal

•The analog signal is a signal that takes continuous range of values to represent information (e.g. sine waves).

•The digital signal is a signal takes discrete values to represent information (e.g. square waves).

Periodic and Aperiodic Signalperiodic signal aperiodic signal

•The periodic signal is a signal that repeats itself after a specific interval of time.

•One completion of the repeating pattern is called a cycle.

•The aperiodic signal is a signal that does not repeat itself after a specific interval of time.

Some Measurements

•Frequency is a measurement of how many cycles occurs in a one second.

•  Period is the time taken to complete one cycle. 

•The amplitude (peak amplitude, Vp ) of a signal is the largest value it takes (is measured from the X-axis, 0 V, to the top of a peak)

•The peak-to-peak amplitude, Vpp , is measured between the maximum positive and negative values

Laboratory Equipments

Base unit

Lab circuit boardOscilloscope

Function generator

Function Generator

•  Function generator  is a device that is used to generate different types of electrical waveforms over a wide range of frequencies.

• A function generator is also known as “signal generator” or “waveform generator”

•  Common waveforms produced by the function generator are the sine, square, triangular and sawtooth shapes.

Function Generator

• Function generators have a few common features:

▫A way to select a waveform type: sine, square, and triangle

▫A way to select the waveform frequency. (the frequency range from 20 Hz to 200 kHz in four ranges).

▫A way to select the waveform amplitude.(the V p-p is from 0 to 20 volt)

▫At least two outputs: The “main" output, which is where you find the desired

waveform.

The second output is used for synchronizing another device to the possibly variable main output signal.

Function Generator

 To select the type of  waveform

Power switchMain output

To adjust the amplitude

To select the frequency

Oscilloscope

•The oscilloscope is basically a graph-displaying device – it draws a graph of an electrical waveform.

•The oscilloscope is typically divided into four sections:

▫The display section.

▫ The vertical controls section.

▫ The horizontal controls section.

▫The trigger controls section.

Oscilloscope

A screen power switch focus knobintensity knob

Volts/Div selector

Y-pos knobs

input channelsSec/Div selector

X-position knob

Display Section

• The display section consists of a screen, a focus knob, and an intensity knob.

• The screen display the signals in a voltage (Y-axis) versus time (X-axis) graph. It is divided into horizontal and vertical lines to create the graticule.

• The graticule is usually laid out in an 8-by-10 division pattern (about 1 cm for a square).

• An intensity control to adjust the brightness of the waveform.

• A focus control to adjust the sharpness of the waveform.

The Vertical Controls Section

• The vertical section controls the amplitude and the position of the waveform vertically.

• This section contains a Volts-per-Division (Volts/Div) selector knob, Y-axis position (Y-pos) knob, the two input channels, and other controllers.

• The Y-pos used to move the waveform up and down.

• The volts/div knob varies the size of the waveform on the screen. It is a scale factor.

• For example if the volts/div is setting to 5 volts, then each of the eight vertical divisions represents 5 volts and the entire screen can display 40 volts from bottom to top.

The Vertical Controls Section

• If the setting is 0.5 volts/div, the screen can display 4 volts from bottom to top, and so on.

•The maximum voltage you can display on the screen is the volts/div setting multiplied by the number of vertical divisions.

•The signal to be viewed on the oscilloscope screen is fed to the input channels (input channel I and input channel II) of the oscilloscope.

The Horizontal Section • The horizontal section controls the position and the scale

of the waveform horizontally.

•  The primary controls in this section are: the Seconds-per-Division (Sec/Div) selector switch and the position knob.

• Use the sec/div control to set the amount of time per division represented horizontally across the screen.

• If the setting is 1 ms, each horizontal division represents 1 ms and the total screen width represents 10 ms,

• The position knob is used to move the waveform left and right

Analog Communications circuit board

•The Analog Communications circuit board is used configure, operate, and troubleshoot the following seven circuit blocks : ▫Amplitude Modulation (AM) Transmitter and

Receiver.▫ Single-Sideband (SSB) Transmitter and

Receiver.▫ Frequency Modulator (FM).▫ Phase Modulator (PM).▫ Quadrature Detector (FM Demodulation).▫Phase-Locked Loop (PLL).▫PLL FM Detector.

Base Units

•The base units provide a means of operating, analyzing, and troubleshooting the lab circuit board.