CRT TV:
• 3 seperate electron guns, one for each of the colours (Red, Green, Blue)
• TV's use electromagnetic deflection rather than electrostatic deflection as it is safer (does not require high voltage) and it has the ability to cover larger surface area
• Screen has three different types of coloured phosphors, each electron gun stimulates its corresponding phosphor (ie "Red" electron gun stimulates Red phosphors)
• Image is formed from two passes of an electron beam. Odd numbered lines first, followed by even lines.
Make sure you know what the electrodes in electron gun, deflection coils and fluorescent screen do.
CRO's
• Uses a cathode ray tube to display an input signal voltage as a waveform
o Voltmeters cannot measure small changing potential differences
o Many physical and biological phenomena can be converted to a voltage signal
o Useful in measuring how a quantity varies with time
• Oscilloscopes usually use electrostatic deflection
• In a CRO, a saw-tooth voltage is applied across the horizontal deflection plates.
o Causes spot to move across the screen at a constant speed
o Moves left to right
o Spot switches off when it reaches the right side of the screen
o Allows the creation of a constant time base
• Vertical deflection is provided by the input voltage, allowing voltage to be plotted as a function of time
o If input voltage varies from zero, the cathode ray is deflected upwards for positive polarity or downwards for negative polarity
o Vertical position changes in response to the input signal