An oscilloscope is an instrument used to measure voltage in an electronic device. It measures voltage against time. Oscilloscopes are used for several applications, especially to test the working condition and voltage of an electronic device; to test the circuitry of new electronic equipment; or to test the electronics of new software.

An analog oscilloscope applies the measured signal voltage directly to the vertical axis which is represented in the electron beam that passes from left to right on the oscilloscope's display screen. There are many kinds of oscilloscopes: analog oscilloscope, digital oscilloscope, digital storage oscilloscope, digital phosphor oscilloscope and digital sampling oscilloscope.

There are several advantages of analog oscilloscopes as compared to other oscilloscopes. Their focus and intensity controls can be adjusted for a sharper and more legible display. Analog oscilloscopes are preferred for displaying real-time rapidly varying signals. Analog oscilloscopes also have a phosphor-based display screen that brightens the trace whenever the signal features occur. This is known as intensity grading. Intensity grading makes the distinguishing of signal details easier.

When the analog oscilloscope's probe is connected to a circuit, it allows the voltage signal to travel to the vertical system of the oscilloscope, or to be more specific, the vertical deflection plates of the cathode ray tube near the screen. These deflection plates create a glowing dot that moves across the oscillator's screen. The dot moves up when there is positive voltage and moves down when there is negative voltage. The dot moves from left to right of the screen because of triggering, a control mechanism for maintaining a steady line or trace on the screen, for stabilizing a repeating signal. The horizontal and vertical deflections cause the dot to be shown in the form of line, which represents voltage.

There are also analog storage oscilloscopes. This indicates an additional feature that makes the trace pattern to stay on the screen for a longer time. This is possible by secondary emission.

Agilent, B+K Precision, EZ Digital, Extech Instruments Corp., Fluke, Instek, International Tools & Technologies, Inc., Iwatsu, Kenwood TMI Corp., LeCroy, Morrow Wave, Tektronix and Yokogawa are some of the popular analog oscilloscope manufacturers. Information about analog oscilloscopes, along with their prices and product facts can be sourced from the internet. There are hundreds of sites that give information about analog oscilloscopes.