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CHAPTER 6
THE OSCILLOSCOPE AND SPECTRUM ANALYZER
LEARNING OBJECTIVES
Upon completing this chapter, you should be able to:
1. Describe the purpose of the CRT used in the oscilloscope.
2. Explain the operation of an oscilloscope.
3. Describe the purpose of the controls and indicators found on an oscilloscope.
4. Describe the proper procedure for using a dual-trace oscilloscope.
5. Describe the accessory probes available for use with a dual-trace oscilloscope.
6. Explain the operation of the spectrum analyzer.
7. Describe the purpose of the controls and indicators found on the spectrum analyzer.
INTRODUCTION
One of the most widely used pieces of electronic test equipment is the OSCILLOSCOPE. An
oscilloscope is used to show the shape of a video pulse appearing at a selected equipment test point.
Although some oscilloscopes are better than others in accurately showing video pulses, all function in
fundamentally the same way. If you learn how one oscilloscope operates, you will be able to learn others.
As you will learn in this chapter, there are many different types of oscilloscopes—varying in
complexity from the simple to the complex. Before we get into our discussion of the dual-trace
oscilloscope, we will first present a general overview of basic single-trace oscilloscope operation. Shortly,
we will see how oscilloscopes use a CATHODE-RAY TUBE (CRT) in which controlled electron beams
are used to present a visible pattern of graphical data on a fluorescent screen.
Another piece of test equipment used is the SPECTRUM ANALYZER. This test equipment is used
to sweep over a band of frequencies to determine what frequencies are being produced by a specific
circuit under test, and then the amplitude of each frequency component. An accurate interpretation of the
display will allow you to determine the efficiency of the equipment being tested.
CATHODE-RAY TUBES
A detailed discussion of CATHODE-RAY TUBES (CRTs) is presented in NEETS, Module 6,
Electronic Emission, Tubes, and Power Supplies. Before continuing with your study of CRTs in this
section, you may want to review chapter 2 of that module.
Cathode-ray tubes used in oscilloscopes consist of an ELECTRON GUN, a DEFLECTION
SYSTEM, and a FLUORESCENT SCREEN. All of these elements are enclosed in the evacuated space
