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


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


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


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