An oscilloscope is basically a graph-displaying device - it draws a graph of an electrical signal. In all automotive applications, the graph shows how signals change over time: the vertical (Y) axis represents voltage, and the horizontal (X) axis represents time.


But don't be fooled - this simple graph can tell you many things about a signal, such as:

* The time and voltage values of a signal (how many volts and when it changes)
* The frequency of an oscillating signal (how fast the voltage is rising and falling)
* The frequency with which a particular portion of the signal is occurring relative to other portions (is there a part of the signal that varies more rapidly up and down than other parts?)
* Whether or not a malfunctioning component is distorting the signal (do the sine waves look more like square waves?)
* How much of the signal is noise and whether the noise is changing with time ('noise' is normally seen as a superimposed signal - jagged edges on a sine wave, for example)