An oscilloscope is a type of electronic test equipment which visually renders the voltage of an electronic signal. Oscilloscopes are also sometimes referred to as (sometimes referred to as scopes or O-scopes. They are used to test and troubleshoot electronic equipment. The scope displays the voltage on a cathode ray tube (CRT) display. A grid is drawn on the screen which is called a graticule and the squares within the graticule are called divisions. This results in a graph where the horizontal axis represents the time and the vertical axis represents the voltage. There are also oscilloscopes which can display multiple waveforms. These are used to compare phase or timing of 2 or more signals.

The oscilloscope repeatedly draws a horizontal line called a trace from left to right across the middle of the screen. If the voltage being measured deviates from zero the trace is deflected up or down on the screen. You can control the speed at which the trace is drawn with the timebase control. This control is calibrated in seconds per division. You can also control the vertical deflection scale with the vertical control. The vertical control is calibrated in volts per division. The trace plots the voltage of the input signal against time.

Modern oscilloscopes generally have a trigger function which has the effect of producing a trace which is more stable. The trigger function causes the oscilloscope to pause when the trace reaches the right edge of the screen. It then waits for the specified event before the next trace is drawn. More often than not the trigger event is the input signal voltage reaching a certain value which can be positive or negative. The result is the resynchronization of the input signal to the timebase. This prevents the horizontal drift of the trace. This has the benefit of allowing the oscilloscope to display periodic signals. Common examples of periodic signals are square waves and sine waves. The triggering function also allows the display of nonperiodic signals such as pulses which do not recur at a fixed rate.

Oscilloscopes are frequently used in troubleshooting electronic equipment which is not working correctly. The ability of an O-Scope to display a signal graphically is a distinct advantage over a voltmeter. Occasionally the pulse's shape is very important from a troubleshooting standpoint. A scope can also let you know if the signal is oscillating. All in all an oscilloscope is an invaluable tool for all electronics technicians and they're a standard on any technician's workbench.