4.7- USING AN OSCILLOSCOPE

Question 1

What does an oscilloscope consist of?

Answer 1

specially made electron tube and associated control circuits

Question 2

What does an electron gun at one end of the glass tube emit and towards where? (oscilloscope)

Answer 2

emits electrons in beam towards fluorescent screen at other end of tube

Question 3

What is emitted where the beam hits the screen? (oscilloscope)

Answer 3

light emitted from spot on screen where beam hits screen

Question 4

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

Answer 4

pd across either pair of deflecting plates

Question 5

What happens to the spot on the screen with no pd across either set of deflecting plates?

Answer 5

spot on the screen stays in the same position

Question 6

What happens to the spot if a pd is applied across the X-plates?

Answer 6

spot deflects horizontally

Question 7

What happens to the spot if a pd is applied across the Y-plates?

Answer 7

spot deflects vertically

Question 8

What is the displacement of the spot proportional to?

Answer 8

displacement of spot proportional to applied pd

Question 9

What are the X-plates connected to?

Answer 9

oscilloscope’s time base circuit

Question 10

What does the X-plates being connected to the oscilloscope’s time base circuit do the spot?

Answer 10

spot moves at constant speed left to right across the screen, then back again much faster

Question 11

What can be done as the spot moves at constant speed across the screen?

Answer 11

x-scale can be calibrated

Question 12

What is the x-scale usually calibrated in? (2) (hint- unit)

Answer 12

milliseconds or microseconds per centimetre

Question 13

What is the pd to be displayed connected to?

Answer 13

Y-plates via Y-input

Question 14

What happens to the spot as the pd to be displayed is connected to the Y-plates via Y-input?

Answer 14

spot moves up and down as it moves left to right across the screen

Question 15

What does the spot trace out as it moves up and down as it moves left to right across the screen?

Answer 15

traces out the wavefront on the screen

Question 16

What is the vertical displacement of the spot proportional to?

Answer 16

vertical displacement of spot proportional to pd applied to Y-plates

Question 17

What is the Y-plate calibrated in?

Answer 17

volts per centimetre (or per division if the grid on the oscilloscope screen is not a cm grid)

Question 18

What is the calibration value of the Y-plate usually referred to as?

Answer 18

Y-sensitivity or Y-gain of the oscilloscope

Question 19

How do you measure the peak pd?

Answer 19

observe waveform height from bottom to top
half this to get the amplitude
multiply Y-gain and amplitude to get peak pd

Question 20

How do you measure frequency of alternating pd?

Answer 20

measure time period:
see what distance one full cycle corresponds to
multiply time base by this distance to get time period
f = 1 / T

Question 21

What can the time base circuit of an oscilloscope be used to trigger? (measuring the speed of ultrasound)

Answer 21

ultrasonic transmitter so it sends out a short pulse of ultrasonic waves

Question 22

What can be used to detect the transmitted pulse? (measuring the speed of ultrasound)

Answer 22

ultrasonic transmitter

Question 23

How can the waveform of the receives pulse be seen on the oscilloscope screen? (measuring the speed of ultrasound)

Answer 23

if receiver signal applied to Y-input of oscilloscope

Question 24

What happens as the pulse takes time to travel from the transmitter to the receiver? (measuring the speed of ultrasound)

Answer 24

it’s displayed on the screen at the point reached by the spot as it sweeps across the left to right

Question 25

How can the travel time of the pulse from the transmitter to the receiver be determines? (measuring the speed of ultrasound)

Answer 25

by measuring the horizontal distance of the screen from the leading edge of the pulse to the start of the spot’s sweep

Question 26

How to calculate the travel time? (measuring the speed of ultrasound)

Answer 26

pulse multiplied by time base control

Question 27

What can be calculated if the distance from the transmitter to the receiver is known?

Answer 27

speed of ultrasound (from distance / travel time)