TABLE OF CONTENTS Introduction ................................................................................................................................ 4 So what exactly is an oscilloscope? ....................................................................................... 4 Signals ....................................................................................................................................... 7 Frequency measurements ..................................................................................................... 7 Amplitude measurements ...................................................................................................... 8 Non-sinusoidal waveforms ................................................................................................... 10 Analog oscilloscopes ................................................................................................................ 11 Analog scope controls ........................................................................................................... 11 Theory of operation .............................................................................................................. 13 Cathode ray tube (CRT) ................................................................................................... 13 Vertical circuits ................................................................................................................. 14 Horizontal and trigger circuits ........................................................................................... 15 Graticule ........................................................................................................................... 16 Delayed sweep ................................................................................................................. 17 Operation of an analog scope .............................................................................................. 18 Vertical coupling ............................................................................................................... 19 Variable adjustments ........................................................................................................ 19 Trigger controls ................................................................................................................. 19 Slow waveforms ............................................................................................................... 20 XY display mode ............................................................................................................... 20 Component test ................................................................................................................ 21 Digital oscilloscopes ................................................................................................................ 23 Digital scope controls ........................................................................................................... 23 Other types of digital oscilloscopes ...................................................................................... 28 Mixed signal oscilloscope (MSO)...................................................................................... 28 USB oscilloscope.............................................................................................................. 28 Handheld oscilloscopes .................................................................................................... 28 Theory of operation .............................................................................................................. 29 Sampling .......................................................................................................................... 30 Dead time ......................................................................................................................... 33 Operation and features ........................................................................................................ 34 The AUTO button .............................................................................................................. 35 Quick help ........................................................................................................................ 35 2 Vertical gain ...................................................................................................................... 36 Vertical coupling ............................................................................................................... 36 Trigger controls ................................................................................................................. 36 Delayed timebase ............................................................................................................. 36 XY display mode ............................................................................................................... 37 Saving waveforms and data ............................................................................................. 37 Network operation ............................................................................................................ 38 Math calculations .............................................................................................................. 39 Recording transient events ............................................................................................... 40 Video triggering ................................................................................................................ 40 Averaging ......................................................................................................................... 40 Peak detection .................................................................................................................. 41 Automatic Measurements ................................................................................................. 42 Reference waveform ........................................................................................................ 43 Recording waveforms ....................................................................................................... 44 Digital filter ........................................................................................................................ 45 Pass/fail testing ................................................................................................................ 46 WaveXpress® ................................................................................................................... 47 Probes ..................................................................................................................................... 48 Probe compensation ............................................................................................................ 50 Probe types .......................................................................................................................... 50 A passive probe and its accessories .................................................................................... 51 Floating a scope ................................................................................................................... 54 Good measurement practices .................................................................................................. 55 Oscilloscope safety .................................................................................................................. 56 Preventing damage to the oscilloscope................................................................................ 56 Glossary .................................................................................................................................. 57 References .............................................................................................................................. 64 3 Introduction This document is a primer on the use and application of analog and digital oscilloscopes (we'll also call them "scopes"). Most of the material is at an introductory level and aimed at helping you understand some of the key features and aspects about oscilloscopes. What we'll cover in this document • Basic characteristics of signals and their terminology • Two predominant types of oscilloscopes available today: analog and digital • Typical oscilloscope controls, features, and theory of operation • Various types of probes available and their use • Oscilloscope guidelines and safety A glossary of terms used in the context of oscilloscopes and the use of oscilloscopes is included at the end of this document. So what exactly is an oscilloscope? An oscilloscope is an electrical measuring device that displays a graph of a voltage as a function of time. This allows a user to make both voltage and time measurements. Many oscilloscopes can display more than one voltage signal on their screen, which gives us the powerful ability to compare the behavior of these signals. Since our brains are good at recognizing patterns, the oscilloscope lets us see patterns in these voltage versus time plots. These patterns and comparisons are the oscilloscope's benefits over a measuring instrument like a voltmeter that just gives us a number. Since many physical properties of interest can be represented by a voltage, the oscilloscope helps us understand how the world changes in time. Many engineers, scientists, and