Cathode Ray Oscilloscope (CRO)
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Transcript of Cathode Ray Oscilloscope (CRO)
Oscilloscope
Tushar Swami 13/0194Prafful Arora 13/0499Anurag Aggarwal 13/1189
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
We would like to express our special thanks of gratitude to our teacher 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
What is an Oscilloscope?
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
Professions using OscilloscopesPhysicists and Researchers
Engineers and Students
Electronic Technicians
Health Care Workers
Sources : http://www.circuitspecialists.com/blog/professions-which-use-oscilloscopes
How an Oscilloscope works?
Click icon to add picture
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.
Electron Gun
Cathode
Control Grid
Aperture
= electron
Control Grid
First Anode
= electron
First Anode
Second Anode
= electron
Second Anode
Screen
= electron
Cathode
Second Anode
Control Grid
First Anode
Screen
= electron
DEFLECTION PLATES
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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
Phosphor
Screen
Electron Gun
Horizontal Plates
Vertical Plates
Sources : http://www.schoolphysics.co.uk/Electrostatics/text/Cathode_ray_oscilloscope/index.html
Electrostatic Focusing
Sources : http://www.circuitstoday.com/crt-cathode-ray-tube
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
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
=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
Sources : http://www.circuitstoday.com/crt-cathode-ray-tube
Electrostatic Deflection
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.
+ +++ +
-- - - - -
++
𝑒−
y
x 𝑣 𝑥
𝑣 𝑥
𝑣❑
Sources : ELECTRONIC DEVICES AND APPLICATIONS :-somnath nair
D – Deflection on screen
d - Distance between deflection plates (meters)
L – Distance from the plates to the screen
l :-Length of the deflection plates (meters)
VD – Deflection voltage (volts)
VA – Accelerating voltage (volts)
D
+ +++ +
-- - - - -
++
𝑒−
y
x
𝑣 𝑦
𝑣 𝑥
𝑣 𝑥
𝑣❑
𝜃
D
D = L + l VD 2 2d VA
SE = D = L VD 2d VA
l l
D is the deflection produced on the screen by DEFLECTING VOLTGE VD.
ELECTROSTATIC DEFLECTING SENSITIVITY (SE ) is the amount of DEFLECTION produced per unit applied voltage.
Sources : ELECTRONIC DEVICES AND APPLICATIONS :-somnath nair
Magnetic deflection
Deflection for short period
Employed in low frequency
region.
Consumes more power.
ELECTROSTATIC
deflectionDeflection for long period.
Employed in high frequency region
Consumes less power.
Screens for CRTScreen 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
What are graticules?
a graticule is part of the visual display, to facilitate measurements.
Sources : Electronic Instrumentation and Measurements - William D.Cooper
Types of graticules External Graticule Internal Graticule
Scale Marked from outside Scale marked from inside It has parallax error It removes the parallax error
parallaxSources : Electronic Instrumentation and Measurements - William D.Cooper
Click icon to add picture
OSCILLOSCOPE PROBES
- in most widespread use- only includes passive elements and may provide 1:1
- expensive and normally reserved for more specialist requirements- has active components
Pass
ive
Active
Sources : Electronic Instrumentation and Measurements - DAVID A.BELL
Types of Oscilloscopes
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
Analog Digital
Different types of Digital Oscilloscopes
Digital Storage Oscilloscopes (DSO)
Digital Phosphor Oscilloscope
Digital Sampling Oscilloscope
Mixed Domain Oscilloscope (MDO)
Mixed Signal Oscilloscope (MSO)
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
OTHER REFERENCES WILLIAM D.COOPER - Electronic Instrumentation and Measurements DAVID A.BELL - Electronic Instrumentation and Measurements H.S. KALSI - Electronic Instrumentation