4.7 Using an oscilloscope

Question 1

What does an oscilloscope consist of?

Answer 1

A specially made electron tube and associated control circuits
An electron gun at one end of the glass tube emits electrons in a beam towards a fluorescent screen at the other end of the tube
Light is emitted from the spot on the screen where the beam hits the screen

Question 2

Oscilloscope: What is the position of the spot of light on the screen affected by?

Answer 2

The pd across either pair of deflecting plates

With no pd across either, the spot on the screen stays in the same position

If a pd is applied across the X plates, the spot deflects horizontally

A pd applied across the Y plates makes it deflect vertically

THE DISPLACEMENT OF THE SPOT IS PROPORTIONAL TO THE APPLIED PD

Question 3

How to display a waveform on an oscilloscope

Answer 3

X plates connected to time base circuit which makes the spot move at constant speed left to right across the screen then back again much faster
X scale can be calibrated usually in milliseconds per cm
Pd to be displayed is connected to the Y plates via the Y input so the spot moves up and down as it moves left to right across the screen while tracing out the waveform
Y input is calibrated in colts per centimetre
Calibration value name -> Y sensitivity or Y gain

Question 4

What can the time base circuit of an oscilloscope be used for

Answer 4

To trigger an ultrasonic transmitter so it sends out a short pulse of ultrasonic waves