4.7 Using an oscilloscope Flashcards
What does an oscilloscope contain?
» Electron tube and assoicated control circuits
How does an oscilloscope work?
» Electron gun at one end of the glass tube emits electrons in a beam
» Electrons hit fluorescent screen at the other end of the tube
» Light is emitted from the spot on the screen where the beam hits the screen
What is the position of the spot of light on the screen is affected by?
» The pd across either pair of deflecting plates
What happens to the spot with no pd across either set of deflecting plates?
» The spot on the screen stays in the same position
What happens to the spot if pd is applied across the X plates?
» Spot will move horizontally
What happens to the spot if a pd is applied across the X-plates?
» Spot deflects vertically
What is the displacement of the spot proportional to?
» The applied pd
What is the X-plates connected to?
» The time base circuit
What does the time base circuit do?
» Makes the spot move at a constant speed left to right across the screen, then back again much faster
What is so important about the spot being moved at constant speed?
» The x-scale can be calibriated - usually in milliseconds or microseconds per centimetre
What is the Y-plates connected to?
» The Pd to be displayed - known as the Y sensitivity
What does the y-sensitivity do?
» The spot moves up and down as it moves elft to right across the screen
» Traces out the waveform on the screen
Why is the y-input calibrated in volts per centimetre?
» As the vertical displacement of the spot is proporitonal to the pd applied to the Y-plates
How can you find the amplitude of the wave?
» Measure from the trough to the peak then divide by 2
How can you find the peak pd?
» Times the y-sensistivity by the amplitude
