Introduction to the Cathode Ray Oscilloscope

Genre: Educational

Year Published: 1970

Creator: Encyclopaedia Britannica Educational Corporation

Format: 16mm

Sound: sound

Description: STUDY GUIDE AVAILABLE HERE (LINK) Just as a microscope might symbolize science in the nineteenth and early twentieth centuries, the cathoderay oscilloscope could well become a symbol of science in our time. This versatile instrument is proving to be an indispensable tool for measurement, display, and analysis in all branches of science and technology.  The film introduces the oscilloscope by demonstrating how early experiments led to the development of the cathode-ray tube, the heart of the oscilloscope. In a cathode-ray tube, electrons are deflected by magnetic and electric fields. In the modern oscilloscope, an electron beam is deflected by electric fields between plates across which a voltage is applied. Vertical beam can show voltage changes, and a precisely timed horizontal sweep permits voltage to be graphed against time. Therefore, the cathode-ray oscilloscope can function as a voltmeter, a clock, and a graph plotter.  Since the oscilloscope responds to voltages, it is used with transducers. Transducers convert physical phenomena such as sound, light, and heat into voltages for analysis on the oscilloscope. The film demonstrates several transducers in use. With a microphone as a transducer, the sounds of speech, music, or a tuning fork may be graphed. The intensity of the flash of light  from a flashbulb or the shutter speed of a movie projector may be graphed by using a photoelectric cell as a transducer. A simple thermocouple made from  twisted wires makes it possible to measure the temperature rise produced by the heat of a candle flame.  Patterns of Lissajous figures can be produced on the cathode-ray oscilloscope screen by applying to the vertical and horizontal deflection plates external signals in the proper ratio of frequencies. These figures are not only useful for testing and analysis, but are of artistic interest as an exciting new form of graphics.