Lab2 - Lab 2 The Oscilloscope motion of free electrons in...

Info icon This preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Lab 2: The Oscilloscope - motion of free electrons in an electric field 1 Introduction The oscilloscope is a very versatile instrument that is used almost universally for data acquisition, and as a diagnostic tool. Its principle of operation is relatively easy to understand. However, students usually react with alarm and confusion when confronted with the numerous buttons and switches on the front panel of the device. This laboratory will hopefully assist you in overcoming any hesitation in using this device. An analogue oscilloscope consists of an electron gun encased in an evacuated narrow glass tube. The tube has a wide end face (coated with a phosphor) on which signals are displayed. In many ways, its construction resembles that of a television tube. Electrostatic fo- cusing plates and electron beam deflection plates are enclosed within the narrow tube and connected to the outside via feed-through elements. This lab will al- low students to understand the principles of such an oscilloscope. An electron beam is produced by electrically heating a metal foil (or filament). Electrons in the foil ac- quire sufficient kinetic energy to escape the foil. A large electric potential difference between the foil and a ring electrode accelerates the electrons. The focus- ing plates shape the cross section of the electron beam. The electron beam can be deflected by uniform elec- tric fields between the deflection plates before hitting the phosphor screen. These electric fields are pro- duced by applying a (voltage) signal to the inputs of the oscilloscope. When the electron beam strikes the phosphor screen, excited atoms in the phosphor con- vert the kinetic energy of the electron beam into light, producing a characteristic glow. A digital oscilloscope does not have an electron beam tube. The input waveform is digitized and displayed on the screen. You will first use a stripped down electron tube to learn how electrons are deflected in a uniform electric field. For the rest of this report, we will refer to this oscilloscope as the cathode ray tube or MT69MT108MT101MT99MT116MT114MT111MT110MT32MT103MT117MT110 MT121 MT49 MT121 MT50 MT76 MT49 MT76 MT50 MT100 MT69 MT69MT108MT101MT99MT116MT114MT111MT115MT116MT97MT116MT105MT99MT32MT100MT101MT102MT108MT101MT99MT116MT105MT111MT110MT32MT112MT108MT97MT116MT101 MT69MT108MT101MT99MT116MT114MT111MT110MT32MT98MT101MT97MT109 MT83MT99MT114MT101MT101MT110 MT80MT97MT114MT97MT98MT111MT108MT97 MT83MT116MT114MT97MT105MT103MT104MT116MT32MT108MT105MT110MT101 Figure 1: Electron beam deflection. NOTE: L 2 L 1 . CRT. The CRT is built so that the deflection plates and other electrodes are clearly visible. The exper- iments will allow you to measure the axial speed of the electron beam. Subsequently, you will learn how a simple waveform can be displayed on the screen. Finally, you will work with a standard laboratory os- cilloscope, learn how to trigger the scope, and display waveforms.
Image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern