Cathode Ray Oscilloscope (CRO)

A detailed presentation about what is a CRO, its every component and how it works. Also enlisting, some of its major applications.

1. Oscilloscope Tushar Swami 13/0194 Prafful Arora 13/0499 Anurag Aggarwal 13/1189

2. OUTLINE What is an Oscilloscope? Professions using Oscilloscope How an Oscilloscope works? Its basic parts and operation Electrostatic Focusing and Deflection Cathode Ray Oscilloscope Types of Oscilloscopes Applications of Oscilloscopes

3. We would like to express our special thanks of gratitude to our t eacher Dr. Amit Pundir and Mr. Raj Shekhar who gave us the golden opportunity to present this wonderful presentation on the topic(OSCILLOSCOPES ), which also helped us in doing a lot of Research and we came to know about so many new things. We are really thankful to them. ACKNOWLEDGEMENT

4. What is an Oscilloscope?

5. We all have seen and drawn graphs in school time. Graph – shows change in a particular quantity or trait with time ( in most cases). But in electronics, it may take ages to plot unless (quantities like voltage). So… in such cases “OSCILLOSCOPE” comes into play. An oscilloscope is a laboratory instrument commonly used to display and analyze the waveform  of electronic signals. In effect, the device draws a graph of the instantaneous signal voltage as a function of time. Sources : http:// www.explainthatstuff.com/howoscilloscopeswork.html http :// whatis.techtarget.com/definition/oscilloscope

6. Professions using Oscilloscopes Sources : http://www.circuitspecialists.com/blog/professions-which-use-oscilloscopes

7. How an Oscilloscope works?

8. Phosphor Screen Electron Gun Horizontal Plates Vertical Plates Generates the beam Electron Beam Deflects Beam instrument employs a Cathode Ray Tube. CRT - Heart of Oscilloscope.

9. Electron Gun

10. Cathode Control Grid Aperture = electron

11. Control Grid First Anode = electron

12. First Anode Second Anode = electron

13. Second Anode Screen = electron

14. Cathode Second Anode Control Grid First Anode Screen = electron

15. DEFLECTION PLATES

16. Electrons are negatively charged particles. Attracted by positive charge or field. So, to deflect the electron beam positive field is used to attract the beam in particular direction. Horizontal Plates Vertical Plates - - - - - + + + + + - ve Field + ve Field = electron Sources : http:// www.schoolphysics.co.uk/Electrostatics/text/Cathode_ray_oscilloscope/index.html

17. Phosphor Screen Electron Gun Horizontal Plates Vertical Plates

18. Sources : http:// www.schoolphysics.co.uk/Electrostatics/text/Cathode_ray_oscilloscope/index.html

19. Electrostatic Focusing

20. Sources : http://www.circuitstoday.com/crt-cathode-ray-tube

21. The electron beam is focused on the screen by an electrostatic lens consisting of two cylindrical anodes called the focusing anode and accelerating anode . The plate A is at potential +E while the plate B is at potential – E. The direction of electric field is From A plate to plate B at right angle to the surfaces  and The equipotential surfaces are perpendicular to the direction of electric field. Sources : http:// electrical4u.com/cathode-ray-oscilloscope-cro

22. When two concentric cylinders with some Potential difference is placed such that an electric field is generated between them. Electrons move in a direction opposite to that of electric field lines and equipotential surfaces are perpendicular to the electric field lines. Force on the electron is exerted in the direction normal to the equipotential surface. Sources : Electronic Engineering Fundamentals

23. =initial velocity of electrons initial velocity of electrons =velocity of electrons after leaving surface V =angel of incidence =angle of refraction sin = sin   Sources : http:// www.circuitstoday.com/crt-cathode-ray-tube

24. Sources : http:// www.circuitstoday.com/crt-cathode-ray-tube

25. Electrostatic Deflection

26. Electron reaches between the deflection plates and are deflected in the attractive force of electric field. Electron enter with velocity and is deflected along the positive –y axis, follows a curved path. It moves in the x direction with velocity and in y - direction with velocity . Acceleration take place in vertical direction.   + + + + + - - - - - - + +   y x       Sources : ELECTRONIC DEVICES AND APPLICATIONS :- somnath nair

27. D – Deflection on screen d - Distance between deflection plates (meters) L – D istance from the plates to the screen l :-Length of the deflection plates (meters) V D – Deflection voltage (volts ) V A – A ccelerating voltage (volts) D + + + + + - - - - - - + +   y x           D

28. D = L + l V D 2 2d V A S E = D = L V D 2d V A l l D is the deflection produced on the screen by DEFLECTING VOLTGE V D. ELECTROSTATIC DEFLECTING SENSITIVITY ( S E ) is the amount of DEFLECTION produced per unit applied voltage. Sources : ELECTRONIC DEVICES AND APPLICATIONS :- somnath nair

29. Screens for CRT Screen of CRT is made up of Phosphor The property of few material (like phosphor) to emit light when stimulated by radiation is called fluorescence . Why phosphor is used ? Fluorescent material have property to continue emitting light even after the source of excitation is over, called phosphorescence . Sources : Electronic Instrumentation and Measurements - DAVID A.BELL

30. What are graticules ?

31. a  graticule   is part of the visual display, to facilitate measurements. Sources : Electronic Instrumentation and Measurements - William D.Cooper

32. Types of graticules External Graticule Internal Graticule Scale Marked from outside Scale marked from inside It has parallax error It removes the parallax error parallax Sources : Electronic Instrumentation and Measurements - William D.Cooper

33. OSCILLOSCOPE PROBES

34. Sources : Electronic Instrumentation and Measurements - DAVID A.BELL

35. Types of Oscilloscopes

36. ANALOGOSCILLOSCOPES implies “ ANALOG ” techniques to create the pattern on the display. DIGITAL OSCILLOSCOPES first coverts the signal into digital format and then processes it. Sources : http:// www.radio-electronics.com/info/t_and_m/oscilloscope/analogue-scopes.php http ://www.saelig.com/miva/graphics/00000001/ds1062ca725.jpg

37. Different types of Digital Oscilloscopes

38. APPLICATIONS OF OSCILLOSCOPES DC/AC Voltage measurement Time/frequency measurements of a particular signal Pulse width measurements Pulse rise time and fall time measurements Phase difference measurements Sources : www.slideshare.net

39. OTHER REFERENCES WILLIAM D.COOPER - Electronic Instrumentation and Measurements DAVID A.BELL - Electronic Instrumentation and Measurements H.S. KALSI - Electronic Instrumentation