Rongge

Circuit symbol for an oscilloscope   Cathode Ray Oscilloscope (CRO) Photograph © Rapid Electronics An oscilloscope is a test instrument which allows you to look at the 'shape' of electrical signals by displaying a graph of voltage against time on its screen. It is like a voltmeter with the valuable extra function of showing how the voltage varies with time. A graticule with a 1cm grid enables you to take measurements of voltage and time from the screen. The graph, usually called the  trace , is drawn by a beam of electrons striking the phosphor coating of the screen making it emit light, usually green or blue. This is similar to the way a television picture is produced. Oscilloscopes contain a vacuum tube with a  cathode  (negative electrode) at one end to emit electrons and an  anode  (positive electrode) to accelerate them so they move rapidly down the tube to the screen. This arrangement is called an electron gun. The tube also contains electrodes t...