The oscilloscope is one of the most important and ubiquitous measuring instrument used in the science industry today. With its wide application range it is a useful tool in medicine, engineering, telecommunications and other sciences. Before the digital revolution, the oscilloscope was composed of a cathode ray tube, amplifiers, time controllers and other electronics that measured voltages and showed them on a screen. Oscilloscopes are used to detect the change of an electrical signal over time and display as continuous graph showing amplitude, frequency, rise time, time interval and others in a repeated pattern continuous shape on the screen. This measuring instrument displays an electric signal measured in a circuit or any other physical quantities (sound for example) that have been converted to an electrical signal. The more recent and modern oscilloscope is entirely digital and is using a combination of a voltage measuring hardware, analog-to-digital converter and software to display measured voltage into digital information.
The analog oscilloscope uses a CRT monitor that is basically an electron "canon", in a vacuum glass tube, that accelerates electrons and projects them into a point at the end of the tube, through an electric field. The end of the tube has a phosphorous coating that glows when is hit by the electron beam. Each of electrons would experience a force induced by the electric field and, as a result the stream is deflected by an amount directly proportional with the strength of the field. The oscilloscope is using separate electric fields for both x and y directions that allow the electron beam to be moved, creating a point at the end of the tube. The electric fields, caused by voltages, are applied to magnetic deflecting plates positioned to redirect the electron beam. The voltage is controlled by amplifiers for both directions x and y. The displacement of the beam is directly proportional to these voltages, generating a simple system to plot a graph.
