An oscilloscope is a device used to measure voltage against time in an electronic instrument. Generally used for various applications, oscilloscopes are especially utilized in testing the circuitry of new electronic equipment, the voltage and working condition of an electronic device or the new software of an electronic instrument.
There are several types of oscilloscopes: analog, digital, digital phosphor, digital storage and digital sampling oscilloscope. The simplest and earliest type of oscilloscope comprises of a vertical amplifier, a cathode ray tube (CRT), a timebase, a power supply and a horizontal amplifier. These are commonly known as the “analog” oscilloscopes.
An analog oscilloscope is simpler in concept compared to a digital oscilloscope, which became popular between 1990s and 2000s. It directly applies measured signal voltage to the vertical axis which is also represented in the electron beam that passes on the display screen of the oscilloscope.
Compared to other oscilloscopes, analog oscilloscopes have several advantages. One of them is the scope’s focus and intensity controls, which can be conveniently adjusted to reveal a more legible and sharper display. An analog oscilloscope also features phosphor-based display to provide brighter trace during occurrence of signal features. Also known as intensity grading, this capability helps users distinguish details of signals easily.
Connecting the analog oscilloscope’s probe to a circuit enables the voltage signal to travel to the scope’s vertical system, or to the cathode ray tube’s vertical deflection plates near the screen.
Depending on how the vertical scale (volts/div control) has been set up, an amplifier helps increase the signal voltage. To reduce the signal voltage, users should use the attenuator.
The signal then directly travels to the vertical deflection plate of the CRT. The applied voltage to the deflection plates produces a glowing dot, which is an electron beam hitting the phosphor within the CRT. A negative voltage causes the downward movement of the dot, while a positive voltage moves the dot upward.
The signal travels to the trigger system of the oscilloscope to trigger a “horizontal sweep” or to start. A horizontal sweep is the action of the horizontal system which moves the glowing dot across the screen. Thus, the horizontal time base moves the glowing dot across the screen within a specific time interval only when the horizontal system has been triggered. Many sweeps in fast sequence cause the glowing dot’s movement to blend into a solid line. The glowing dot can also sweep up to 500,000 times each second across the screen.
The vertical deflection and the horizontal sweeping action draw a graph of the signal on the display. To produce a clear picture, the trigger stabilizes repeating signals and ensures that the sweep starts at a similar point of a repeating signal.
In fine, to use an analog oscilloscope, the three basic settings that users should adjust to accommodate an incoming signal are the time base, the amplification or attenuation of the signal and the triggering.
Hendrix Musonda says
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