Cathode Ray Oscilloscope CRO

2. TOPICS COVERED
 Introduction to CRO
 Block diagram of CRO
 Detailed description of CRT
 Multi –Input Oscilloscope
 Lissajous Patterns
 Types of Oscilloscope and it’s application

3. HOW A CRO LOOKS LIKE

4. INTRODUCTION TO CRO
 Versatile electronic instrument giving visual display
of signals
 Used for measurement of frequency , amplitude,
phase etc.
 Also used in determining the nature and
characteristics of various components.
 Has a high bandwidth range thus making it a
sensitive and accurate device.
 Easier to use as the internal routine act as a guide to
the user.

5. BASIC DIAGRAM

6. ANOTHER SCOOP….

7. WORKING OF A CRO

8. The main parts of Cathode
Ray Tube are:
 Electron Gun Assembly
 Focusing Anodes
 Deflection Plates
Assembly
 Screen for CRT

14. Multi-Input Oscilloscope
Oscilloscope can have multiple input and display
facilities.

15. The most common one is of - TWO INPUTS
.
Although FOUR and EIGHT inputs are available
for special applications

16. There are primary two types of multi-
input oscilloscope :-
Single Beam Oscilloscope
Dual Beam Oscilloscope
Both of them can be converted into a
further
Number of traces.

17. Dual Trace Oscilloscopes

18. In this oscilloscope two separate
vertical input channels are used.
There are two common operating
modes for the Electronic Switch, called
Alternate and Chop which can be
selected from the instrument’s front
panel.
Dual Trace Oscilloscopes

19. BLOCK DIAGRAM

20. Dual Beam Oscilloscope
The Dual Beam Oscilloscope has two
separate electron beams , and therefore
two completely separate vertical
channels.

21. There are two methods used for
generating the two electron beams
within the CRT.
The first method is :-
Double gun tube
Split Beam

22. Multiple input CRO works in
following two modes
• alternate mode
• chopped mode

23. Alternate mode
In alternate mode the an electronic
switch alternates between sig A & B.

24. Waveform in alternate mode

25. Chopped mode
In the chopped mode the switch
free runs at very high frequency.

26. Waveform of Chopped Mode

27. Pattern
When two sinusoidal voltage signals of
equal frequency having some phase
difference are applied to the deflection
plates of CRO, a straight line or an
ellipse appears on the screen these
figures are called Lissajous figures or
Lissajous curves or pattern.

28. Some examples of lissajous figures……..

29. With the help of lissajous figures
we can measure…….
Frequency
Phase

30. Frequency
Measurement
Fx/Fy = Hp/Vp
Fx = Unknown frequency
Fy = Known frequency
Hp = Points on horizontal tangencies
Vp = Points on vertical tangencies

31. Phase
Measurement
sin Ф = c/b

32. Digital Storage
Oscilloscope

33. BLOCK DIAGRAM OF DSO

34. Advantage Of DSO
Stores waveform for infinite time
Digitize waveform can be processed in any way
Writing speed is more
Processing of signal is easy

35. Analog Storage Oscilloscope

36. Trace storage is an extra feature
They used direct-view storage CRTs
The storage is accomplished using the
principle of secondary emission
Briefings

37. Data can be stored
to infinite time
Image quality is
good
Writing speed is
high
Processing of
signal is easy
Data can be stored
for finite time
Image quality is not
poor
Writing speed is
poor
Processing of signal
is difficult
Difference between ASO & DSO
DSO ASO

38. THANK
u