oscilloscope

As nouns the difference between voltmeter and oscilloscope

is that voltmeter is an instrument for measuring electric potential in volts while oscilloscope is an electronic measuring instrument that creates a visible two-dimensional graph, on a screen, of one or more continuously varying voltages or currents.

As nouns the difference between oscilloscope and vectorscope

is that oscilloscope is an electronic measuring instrument that creates a visible two-dimensional graph, on a screen, of one or more continuously varying voltages or currents while vectorscope is a special oscilloscope that displays an X-Y plot of two signals so as to indicate their relationship.