1 Oscilloscope 2008

1 Oscilloscope 2008 - O.1 OSCILLOSCOPE PRINCIPLE O F OPERA...

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O.1 Hermann Wellenstein Spring 2008 OSCILLOSCOPE PRINCIPLE OF OPERATION AND BEATS A. INTRODUCTION The purpose of this experiment is to make you familiar with the principle and operation of the oscilloscope . This instrument is found in most science laboratories where time varying signals are recorded and, in Physics 18b, we will need it for several of our experiments. To fully understand the operation of an oscilloscope, you would have to know quite a bit about atomic physics and electronics, both of which are topics of this semester. However, we want to use the oscilloscope right from the beginning. It is possible to understand the principle just from a logical point of view so "The Oscilloscope" will be our first experiment.
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OSCILLOSCOPE O.2 Hermann Wellenstein Spring 2008 B. THE PRINCIPLE OF THE OSCILLOSCOPE Introduction The cathode-ray tube (CRT) is the indicating device for an oscilloscope. It consists of the so-called "electron gun," and the deflection plates combined in a vacuum tube with an enlarged end, as shown in Figure 1. The end of the tube is coated with various phosphors which emit visible phosphorescent radiation at the point of bombardment with electrons. The purpose of the electron gun is to produce a beam of electrons that are focused to a sharp point at this fluorescent screen. The intensity of the emitted visible light depends on the speed and number of electrons per unit time striking a given area of the screen. By partially surrounding the cathode with a metal grid, and applying a voltage so that the grid is negative with respect to the cathode, the rate of electron flow through the grid can be regulated. The intensity control is a front panel adjustment on the oscilloscope. Focus To obtain the point source of electrons on the screen, it is necessary to focus and accelerate the electrons. The electrostatic field that exists between the two hollow cylindrical anodes provides the necessary focusing of the electron beam. The diverging electrons entering the first hollow anode are forced to converge because of the field that
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1 Oscilloscope 2008 - O.1 OSCILLOSCOPE PRINCIPLE O F OPERA...

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