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OSCILLOSCOPE & OSCILLOSCOPE &
SIGNAL GENERATORSIGNAL GENERATOR
OSCILLOSCOPE & OSCILLOSCOPE &
SIGNAL GENERATORSIGNAL GENERATOR
LECTURER: NURHANUM BINTI OMARLECTURER: NURHANUM BINTI OMAR
CHAPTER 3
3.1.1 Define of Oscilloscopes
Oscilloscope is a device that allows the amplitude of electrical
signals, whether they be voltage, current, power, etc., to be
displayed primarily as a function of time ( the basic instrument for
the study all types of waveforms).
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3.1.2 Explain the functions of
Oscilloscope
The main functions of oscilloscope are:
i. Measure the voltage (AC or DC)
ii. Measure the time and frequency
iii. Measure the phase differential between two
waveforms
3.1.3 Classify types of Oscilloscope
(analogue and digital)
Oscilloscopes can be classified into two categories:
i. Analogue
→ Works with con&nuously variable voltages.
→ Works by directly applying a voltage being measured to an
electron beam moving across the oscilloscope screen.
→ The voltage deflects the beam up and down propor&onally,
tracing the waveform on the screen.
→ This gives an immediate picture of the waveform.
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3.1.3 Classify types of Oscilloscope
(analogue and digital) (cont…)
ii. Digital
→ Works with discrete binary numbers that represent voltage
samples.
→ Samples the waveform and uses an analog-to digital
converter (or ADC) to convert the voltage being measured
into digital information.
→ It then uses this digital informa&on to reconstruct the
waveform on the screen.
3.1.4 Block diagram of an analogue
oscilloscope.
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3.1.5 Block diagram of an digital
oscilloscope.
3.1.6 Basic functional block diagram
of an analogue oscilloscope
• When you connect an oscilloscope probe to a circuit, the voltage
signal travels through the probe to the vertical system of the
oscilloscope.
• Depending on how you set the vertical scale (volts/div control), an
attenuator reduces the signal voltage or an amplifier increases the
signal voltage.
• Next, the signal travels directly to the vertical deflection plates of
the cathode ray tube (CRT).
• Voltage applied to these deflection plates causes a glowing dot to
move. (An electron beam hitting phosphor inside the CRT creates
the glowing dot.) A positive voltage causes the dot to
move up while a negative voltage causes the dot to
move down.
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3.1.6 Basic functional block diagram
of an analogue oscilloscope (cont…)
• The signal also travels to the trigger system to start or trigger a
‘horizontal sweep’. Horizontal sweep is a term referring to the action of
the horizontal system causing the glowing dot to move across the screen.
• Triggering the horizontal system causes the horizontal time base to move
the glowing dot across the screen from left to right within a specific time
interval.
• Many sweeps in rapid sequence cause the movement of the glowing dot
to blend into a solid line. At higher speeds, the dot may sweep across the
screen up to 500,000 times each second.
• Together, the horizontal sweeping action and the vertical deflection
action trace a graph of the signal on the screen. The trigger is necessary
to stabilize a repeating signal. It ensures that the sweep
begins at the same point of a repeating signal.
3.1.7 Basic functional block diagram
of an digital oscilloscope
• Some of the systems that make up digital oscilloscopes are the same as
those in analogue oscilloscopes. However, digital oscilloscopes contain
additional data processing systems.
• With the added systems, the digital oscilloscope collects data for the
entire waveform and then displays it.
• When you attach a digital oscilloscope probe to a circuit, the vertical
system adjusts the amplitude of the signal, just as in the analogue
oscilloscope.
• Next, the analogue-to-digital converter (ADC) in the acquisition system
samples the signal at discrete points in time and converts the signals
voltage at these points to digital values called sample points.
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3.1.7 Basic functional block diagram
of an digital oscilloscope (cont…)
• The horizontal systems sample clock determines how often the ADC takes
a sample.
• The rate at which the clock "ticks" is called the sample rate and is
measured in samples per second.
• The sample points from the ADC are stored in memory as waveform
points. More than one sample point may make up one waveform point.
• Together, the waveform points make up one waveform record. The
number of waveform points used to make a waveform record is called
the record length.
• The trigger system determines the start and stop points of the record.
The display receives these record points after being stored in memory.
3.1.8 Advantages and disadvantages
digital oscilloscope
Advantages Disadvantages
High-accuracy measurements Can be more costly
Display storage Can be less intuitive to operate because
they typically have more features)
Bright, well-focused display at virtually
sweep speed
Pre-trigger viewing capability
Peak/glitch detection
Automatic measurements
Computer, printer/plotter connectivity
Waveform processing capability including
waveform math functions
Display modes like averaging and infinite
persistence
Self calibration
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3.1.9 Advantages and disadvantages
analogue oscilloscope
Advantages Disadvantages
Familiar controls Low accuracy
Instantaneous display updating for real-
adjustments
Display flicker and/or dim display
Direct, dedicated controls for No pre-trigger viewing capability
Adjustments like vertical sensitivity,
time base speed, trace position and
trigger level low cost.
Limited bandwidth
Higher cost of ownership
Limited measurement capability
3.2 Front Panel of an Analog
Oscilloscope
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• POWER SWITCH ON/OFF
Main power switches of the instrument. When this switch is turned
on, the LED above the switch is also turned ON
• POWER LAMP
This LED lamp lights when power is turned ON
• INTENSITY KNOB
It can control the brightness of the spot or trace.
• FOCUS KNOB
After obtaining appropriate brightness with intensity, adjust focus
for clearest line
3.2.1 Explain function of Display
Controls
• TRACE ROTATION KNOB
This knob is used to correct the horizontal trace when it becomes
slanted with respect to the horizontal scale, due to the effect of
magnetic fields
• SCALEILLUM KNOB
This is used to adjust scale brightness. If this knob is turned
clockwise, brightness is increased. This feature is useful for
operation in dark places, or when taking pictures
• CAL 0.5V TERMINAL
Outputs a 0.5V p-p 1 KHz rectangular wave for calibrating probes
GND TERMINAL
This is a grounding terminal
3.2.1 Explain function of Display
Controls (cont…)
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• CH1 INPUT CONNECTOR
This is a BNC connector used for vertical input CH1. The signal applied to
this connector when in the X-Y mode becomes the X-axis signal.
• CH2 INPUT CONNECTOR
This is a BNC connector used or vertical input CH2. The signal applied to
this connector when in the X-Y me ie becomes the Y-axis signal.
• AC-GND-DC SWITCH
Select following input coupling options for CH1 and CH2
AC: blocks dc signal component allowing only AC signal to pass into
attenuator
GND: input signal is switch off and attenuator is grounded
DC: dc coupling, all signal are directly connected to attenuator
3.2.2 Explain function of Vertical
Controls
• VOLTS/DIV SELECTOR SWITCH
This is a step attenuator switch adjusting the vertical deflection sensitivity.
Set to the position which displays the input signal at the most convenient
height on the CRT.
• VARIABLE KNOB
The fine adjustment is used for varying the vertical-axis deflection
sensitivity continuously. If this knob is completely counter clockwise the
vertical sensitivity is reduced to less than 1/2.5 of VOLTS/DIV switch
setting. This knob is used for comparing two waveform and rise time
measurement. However this knob is normally in the locking position.
• PULL X5 MAG
When the pull x5 Mag is pulled out, the vertical axis gain is magnified 5
times, the maximum sensitivity becomes 1mV/div
3.2.2 Explain function of Vertical
Controls (cont…)
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• 20MHz BANDWIDTH
The frequency bandwidth of vertical axis is limited to 20MHz. This knob
can be used when you cannot synchronize the signal by high frequency
noise or expanded trace.
• ALT/CHOP
When the vertical mode is in dual, this button can display ALT and CHOP
mode. ALT mode is a sequential display mode with one cycle of signal
between CH1 and CH2. CHOP mode is a sequential display mode with a
frequency step of approximately 220MHz between CH1 and CH2.
• POSITION
Used to move the CHI or CH2 trace up or down on the CRT screen
3.2.2 Explain function of Vertical
Controls (cont…)
• INVERT SWITCH
When the invert push button is pressed, the polarity of the input signal
applied to CH2 is inverted. This function is convenient when 2 waveforms
of difference are compared, or for displaying the CHI and CH2 difference
waveform using ADD.
• MODE SELECTOR SWITCH
Selects vertical axis operating mode
CHI: only the signal applied to CH1 is displayed on the screen
CH2: only the signal applied to CH2 is displayed on the screen
DUAL: when both CH1 and CH2 buttons are pushed in the signals applied
to CH1 and CH2 input are displayed on the screen
ADD: display the algebraic sum of the CHI and CH2 input voltage
3.2.2 Explain function of Vertical
Controls (cont…)
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• A TIME/DIV
Selects sweep speed from 0.05μs/div to 0.2μs/div in 21 calibrated steps.
• HORIZONTAL POSITION
The trace can be moved in a horizontal direction. Tuning this knob
clockwise moves the trace towards the right, turning the knob is counter
clockwise moves the trace towards the left.
• PULL X10 MAG
When pulled out, the trace will be magnified by a factor of 10 times. The
sweep time becomes 1/10 of the indicated on-the time/div switch, (e.g.
100μs/div becomes 10μs/div for X10 MAG). To magnify a portion of a
waveform: Move the waveform of interest to the centre gratitude on the
horizontal scale.
3.2.3 Explain function of Horizontal
Controls
• A, B, ALT (H DISPLAY)
This switch selects the sweep method of A, B. When both A and B buttons
are pushed in, it was display B sweep which was duplicated by A sweep
and 2 trace of B sweep simultaneously.
• X-Y
Displays the CH1 and CH2 input signal as an X, Y graph. The vertical
deflection signal is applied to the CH1 input and the horizontal deflection
signal is applied to the CH2 input. The CH2 Vertical position control is used
for the positioning the X, Y display on the vertical axis the horizontal
position control positions the X, Y display on horizontal axis of CRT.
• TRACE SEPERATION
This trace separation controls the vertical position interval of A sweep and
B sweep at the sweep mode is A ALT B.
3.2.3 Explain function of Horizontal
Controls (cont…)
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• DLY POS
Adjusts to starting with B sweep during the A sweep periods.
• VARIABLE
When this knob is turned all the way clockwise (cal) the sweep is indicated
by the A time/diy switch, if the knob is turned all the way counter
clockwise the sweep is less than ½ of the A time/div setting. During normal
operation, this knob is turned to the CAL position.
3.2.3 Explain function of Horizontal
Controls (cont…)
• B TRIS'D
This knob selects between continuous delay and triggered delay. For
continuous delay (normal state), the B sweep starts immediately after the
sweep delay time determined by A time/div switch (19) and delay pos (25).
For triggered delay (the knob is pushed), the sweep starts with B trigger
signal after the continuous delay time.
• TRIGGER SOURCE SELECTOR SWITCH
Selects sweep trigger signal source.
INT: The input signal applied to CH1 or CH2 becomes the trigger signal
CH2: The input signal applied to CH2 becomes the trigger signal
LINE: The power line frequency becomes the trigger signal source
EXT: The external signal applied to EXT input becomes the trigger signal.
This is used when the trigger signal is external the vertical
input signal
3.2.4 Explain function of Trigger
Controls
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• TRIG LEVEL KNOB
This control sets the amplitude point on the trigger waveform that will
start the sweep.
Pull Slope knob
Selects the polarity of the slope the trigger source waveform will start the
sweep.
(+) Slope is selected when the pull slope knob is in normal position
(-) Slope is selected when the pull slope knob is pulled out.
• HOLD OFF
By the operation of Hold Off, complicated repetitive signals can be
captured.
3.2.4 Explain function of Trigger
Controls (cont…)
• TRIG-MODE SWITCH
Auto: Sweep continuously runs in the auto sweep mode. A trace will be
displayed even when there is no input signal or when the input waveform
is not triggered. A stationary waveform will be displayed when the input
waveform is properly triggered.
Norm: A trace will be displayed only when the input waveform is present
and is properly triggered. There will be no trace displayed on the CRT if
there is no input signal or if the input signal is not synchronized. Normal
sweep is used when the input signal's frequency is less than 2LHz.
TV-H: Effective when trig mode is set to TV, and is used when the
horizontal of the TV signal is to be synchronized.
TV-V: Effective only when trig mode is set to TV, and is used when the
vertical of the TV signal is to be synchronized.
*Both TV-V and TV-H are synchronized only when the trigger
signal is (-).
3.2.4 Explain function of Trigger
Controls (cont…)
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• Probe is more than a cable with a clip-on tip.
• It is a high-quality connector, carefully designed not to pick up stray
radio and power line noise.
• Probes are designed not to influence the behaviour of the circuit
you are testing.
• However, no measurement device can act as a perfectly invisible
observer.
3.3.1 Define of Oscilloscope Probes.
3.3.2 Classify types of Oscilloscope
Probes.
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3.4.1 Prepare procedure for calibrate
Oscilloscope.
• Turn on oscilloscope. Allow it to warm up for approximately 10
minutes. Letting the oscilloscope warm up prevents damage to its
cathode ray tube.
• A green light is show on the CRT screen when the oscilloscope is
ready. The green light should run across the screen horizontally and
should be in the centre of the screen.
• Adjust the position knob on the oscilloscope by and turn it
clockwise or counter clockwise until this line is at the centre of
the screen. If the line shows up as a green dot moving across the
screen, adjust the time/div knob until the dot appear as a line and
then centre it.
3.4.1 Prepare procedure for calibrate
Oscilloscope.
• Usually an oscilloscope has two channels CH1 and CH2. Connect
your oscilloscope probe to CH1.
• Find the voltage selector switch and set it to AC volts.
• Find CAL connector. It looks like a small enclosed hook, similar to
the eye of a needle.
• Attach the oscilloscope probe to CAL connector. Ground the
ground wire. A peak to peak square wave one volt above the centre
division and one volt below the centre division. This means the
oscilloscope is correctly calibrated at 2 Vpp.
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3.4.2 Connection between Signal Generator
and Oscilloscope for signal
measurement.
3.4.3 Using Oscilloscope To Measure
Voltage, Frequency, Time And Phase Angle
• Voltage (V) :
= No. vertical division x volt/div
x probe { x1 or x10 }
• Period, T (s) :
= No. Horizontal division x
time/div
• Frequency measurement,
f(Hz):
= 1 / period
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3.4.3 Using Oscilloscope To Measure
Voltage, Frequency, Time And Phase Angle
• Using oscilloscope to measure voltage
If the setting VOLT/DIV = 1V.
Voltage peak-to-peak = Volt/Div X Div
Example :
Voltage peak–to-peak = Volt / Div X Div
= 1 Volt / Div X 10 Div
= 10 Vp-p
3.4.3 Using Oscilloscope To Measure
Voltage, Frequency, Time And Phase Angle
• Using oscilloscope to measure frequency
If the setting TIME/DIV = 0.2ms.
Frequency= 1 / T
Where T = Time / div x Div
So, Frequency = 1
[Time / div] x div
Example :
Frequency = 1
[Time / div] x div
Frequency = 1
0.2ms x 10 div
Frequency = 500 Hz
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3.4.3 Using Oscilloscope To Measure
Voltage, Frequency, Time And Phase Angle
a) Voltage measurement (V)
(i) V = 4 x 2 x 1 = 8 Vpp (ii) V = 2 x 2 x 1 = 4 Vp
b) Period (s) = 4 x 1 ms/div = 4 ms
c) Frequency measurement (Hz) = 1/T = 1/4ms = 1 kHz
3.4.3 Using Oscilloscope To Measure
Voltage, Frequency, Time And Phase Angle
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3.4.4 Evaluate the specification of
analogue Oscilloscope
To use an analogue oscilloscope, three basic setting accommodate an
incoming signal:
a. The attenuation or amplification of the signal
Use the volt/div control to adjust the amplitude of the signal before it
is applied to the vertical deflection plates.
b. The time base
The time/div control to set amount of time per division represented
horizontally across the screen.
c. The trigger of the oscilloscope
Use the trigger level to stabilize a repeating signal, as well as
triggering on a single event. Also adjust the focus and
intensity controls to create a sharp and visible display.
3.5 Introduction to signal generator
• A signal generator is a test device which generates an alternating
voltage signal suitable for test purposes.
• The signal generator is used primarily in the alignment of tuned
circuits.
• A signal generator is classified according to its frequency and is one
of two types: audio frequency or radio frequency.
a. Audio frequency generators produce signals with a frequency
range from 20 Hz to 20 kHz.
b. Radio-frequency generators produce signals covering a range of
frequencies from 10 kHz to 10 GHz.
• Many radio-frequency generators have audio outputs separately
available through front panel jacks. These outputs are
normally 100 Hz and 400 Hz.
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3.5.1 Audio signal generators.
• Audio signal generators produce stable audio-frequency signals
used for testing audio equipment.
• Video signal generators produce signals which include the audio
range and extend considerably further into the RF range.
• These generators are used in testing video amplifiers and other
wideband circuits.
3.5.2 Classify types of signal generator.
• Audio signal generators produce stable audio-frequency signals
used for testing audio equipment.
• Video signal generators produce signals which include the audio
range and extend considerably further into the RF range.
• These generators are used in testing video amplifiers and other
wideband circuits.
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3.5.2 Classify types of signal generator.
• Video signal generator :
A device which outputs predetermined video and/or television
waveform and other signals used to stimulate faults in, or aid in
parametric measurements of television and video systems.
• Pitch generator:
- A types of signal generator optimized for use in audio and
acoustics applications.
- Sophisticated pitch generators will also include sweep generators
a function which varies the output frequency over a range.
- Pitch generators are typically used in conjunction with sound
level meters, when measuring the acoustics of a room or a sound
reproduction system, and/or with oscilloscopes or
specialized audio analyzers.
3.5.2 Classify types of signal generator.
• Arbitrary waveform generators (AWG):
- Sophisticated signal generators which allow the user to generate
arbitrary waveforms, within published limits of frequency range,
accuracy and output level.
- Unlike function generators, which are limited to a simple set of
waveforms; an AWG allows the user to specify a source
waveform in a variety of different ways.
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3.5.3 Explain Standard Signal Generators.
• Produces known and controllable voltages
• Used as power source for measurement of gain, signal to noise ratio,
bandwidth, standing wave ratio, and other properties.
• Extensively used in testing of radio receiver and transmitter.
• The output signal can be Amplitude Modulated (AM) or Frequency
Modulated (FM).
3.5.4 Explain Function Generators.
• Produce different waveforms of adjustable frequency
• Common output waveform are sine, square, triangular and saw tooth
• The frequency may be adjusted, from a fraction of a hertz to several
hundred kHz
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3.5.5 Front Panel of a Signal Generators.
3.5.5 Front Panel of a Signal Generators.
Frequency Selection Group
� Range switch: Provide seven fixed decades of frequency
� Multiplier: Variable potentiometer allowing frequency setting
between fixed range.
Sweep Group
� The sweep group can frequency sweep any of its function outputs.
� It could be swept up or down in frequency using linear or log sweeps.
� Unlike function generators, there are no annoying discontinuities or
band-switching artifacts when sweeping through certain frequencies.
� Two sweep marker frequencies can be specified.
� When the sweep crosses either of the marker frequencies, a TTL
transition is generated at the rear-panel output to allow
synchronization of external devices.
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3.5.5 Front Panel of a Signal Generators.
Amplitude Modulation Group
� To provide 20dB of attenuation of the output waveform selected by
function switch.
DC offset Group
� To allow the DC level of the output waveform to be set as desire.
Output Group
� Used to adjust the amplitude of the generator’s out signal.
� The group consists of the amplitude control knob, the three
attenuation buttons and the fused 50Ω BNC connector.
Function or Waveform group
� To provide selection of desired output waveform.
(Square, triangle and sine waveforms are provided)
3.5.5 Front Panel of a Signal Generators.
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3.5.6 Connection Between Signal Generator
& Oscilloscope For Signal Measurement
� Connect the oscilloscope probe and signal generator.
� Switch on the signal generator and adjust the output level to produce
a visible signal on the oscilloscope screen.
� Adjust TIME/DIV and VOLTS/DIV to obtain a clear display and
investigate the effects of pressing the waveform shape buttons.
� The rotating FREQUENCY control and the RANGE switch are used
together to determine the frequency of the output signal.
3.5.6 Connection Between Signal Generator
& Oscilloscope For Signal Measurement
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THANK YOU
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