CRO Display

• The CRO display is simply a Cathode Ray Tube within which electrons are deflected to "trace" the input signal(s) in a visible form.

  

• The display is shown above and has nine divisions on both the X and Y axes. These divisions are used to measure the amplitude of the signal ( In volts ) on the Y-axis and the Period of the signal ( In seconds ) on the X-axis.

The Red line on the diagram on the left represent the most useful site to set the zero axis of the horizontal trace ( this applies when the input signal is zero volts ). This is because this site allows a signal to be viewed on the largest scale possible ( This increases measurement accuracy ). The Red line is situated in the middle of the display which is most useful if the measurement being made is of an A.C. signal as we require the signal to be visible on both sides of the zero axis. It is also useful if we are unsure of the type of signal which we are measuring.

The example on the left is an A.C. signal that does not have a zero voltage axis in the center of the display which leaves us with a reduced viewing area. This does not allow us to make the most accurate measurement possible

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Revised: Friday, 17 July 1998