Technocrats institute of technology (Excellence)

PRESENTED BY :

VIPUL POPHALERATNESH SAHURAGHURAJ SINGH DODIYASANDEEP KUMAR GUPTA

Guided By :

Mohd. Aslam Sir

OSCILLOSCOPE

CATHODE

RAY

INTRODUCTION:• Oscilloscope is an very important test instrument in electrical and electronics field.• It is used to look at the 'shape' of electrical signals by

displaying a graph of voltage against time on its screen.• It is like a voltmeter with the valuable extra function of showing how the voltage varies with time.

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CATHODE RAY OSCILLOSCOPE Popular instrument to show

time, voltage both DC and AC. Shows Volts / Time.

Display waveforms. Spectrum scope shows volts to Frequency

Cathode (-ve ) is heated, emits electrons,

accelerated toward a (+ve) fluorescent screen. Intensity grid, Focus grid, Accelerating anode. (Electron gun)

WHAT IS AN OSCILLOSCOPE ?

An oscilloscope a device that displays a graph of an electrical signal. the vertical (Y) axis represents voltage and the horizontal (X) axis represents time. The intensity or brightness of the display is sometimes called the Z axis.

 History of CRO >>

The earliest mode of creating an image of waveform was through a labourious and painstaking process. This was known as Hand-drawn Oscilloscope..

In the late 19 century , CRT were developed, then with the help of crt “Karl Ferdinand Braun” invented the first crt oscilloscope by applying an osc!llating signal to electrically charged deflecing plates…

Main Units Of CRO

Power Supply UnitCathode Ray TubeVertical AmplifierHorizontal AmplifierTime Base Generator(Sweep Generator)Trigger CircuitDelay Line

BASIC CATHODE RAY TUBE :

The CRT uses an evacuated glass envelope which is large, deep, heavy, and relatively fragile.

Electron gun

Deflection system

Fluorescent screen

VERTICAL AMPLIFIER >>

HORIZONTAL AMPLIFIER >>

TIME BASE GENERATOR >>

TRIGGER CIRCUIT >>

<< DELAY LINE:

ElectroStatic Focussing

From figure V1T = V1 sin θ1, V2T = V2 sin θ2

But V1T = V2T

V1 sin θ1 = V2 sin θ2

Or   V2/V1 = sin θ1 / sin θ2

This the reason why focussing system in CRT is termed as “ ELECTRON LENS ”

The pre-accelerating and accelerating anodes are connected to the same potential while focussing anode is connected to lower potential.

On account of potential difference between focussing and 2 accelerating anodes ,a non-uniform field exists on each of 2 ends of focussin g anode . The surfaces thus form, “ DOUBLE CONCAVE LENS ”.

Electrostatic Deflection

D= SldEd

2dEa S=Distance between screen and centre Of deflecting plates Ed=Potential between deflecting plates ld=Length of deflecting plates d=Distance between deflecting plates Ea=Voltage of pre-accelerating anode

Control The Brightness By Controlling Electron Flow :

To focus the electron into narrow beams on the screen.

Accelerates the electron

Electron beam:

Working Principle:It basically works on the amplifier and triggering networks.

O/PScreen

Power

Intensity

Focus

Volt/Div Channel

Time/Div

Oscilloscope

Panel Function

VOLTS/DIV Select the vertical deflection factor of the CRT display

TIME/DIV Select the horizontal deflection factor of the CRT display

INTEN (Intensity) Control

The INTEN (intensity) control (sometimes called BRIGHTNESS) adjusts the brightness of the beam on the CRT. The control is rotated in a clockwise direction to increase the intensity of the beam and should be adjusted to a minimum brightness level that is comfortable for viewing.

FOCUS and ASTIG (Astigmatism) Controls

The FOCUS control adjusts the beam size. The ASTIG (astigmatism) control adjusts the beam shape. The FOCUS and ASTIG controls are adjusted together to produce a small, clearly defined circular dot

TRACE ROTATION Control

The TRACE ROTATION control allows for minor adjustments of the horizontal portion of the trace so that you can align it with the horizontal lines on the graticule.

BEAM FINDER Control When pushed, the BEAM FINDER pulls the beam onto the screen so that you can use the horizontal and vertical POSITION controls to center the spot.

Horizontal and Vertical POSITION Controls

The horizontal and vertical POSITION controls are used to position the trace. Because the graticule is often drawn to represent a graph, some oscilloscopes have the positioning controls labeled to correspond to the X and Y axes of the graph. The X axis represents horizontal movement; the Y axis represents the vertical movement.

AC-GDN-DC AC- Ac SignalGDN - grounding the signalDC- Dc Signal

APPLICATIONS OF OSCILLOSCOPES:• 1. Ac & Dc voltage measurement.• 2. Measurement of the voltage between two points on the waveform• 3. Elimination of undesired signal components• 4. Time measurements• 5. Time difference measurements• 6. Pulse width measurements• 7. Pulse risetime and falltime measurements• 8. Phase difference measurements• 9. Frequency measurements• 10. Relative measurements• 11. Sweep multiplication (magnification)• 12. Application of x-y operation