Analog Oscilloscopes

Written by Patty Yu
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Just like any other electronic equipment, oscilloscopes may be categorized as either analog or digital. Either kind of oscilloscope is usually sufficient for many applications, but specific applications may require the individual characters either an analog or digital oscilloscope has to offer. Digital oscilloscopes are further classified into storage, phosphor, and sampling oscilloscopes.

Characteristics of Analog Oscilloscopes

Analog oscilloscopes apply the measured signal voltage directly to its screen using an electron beam (usually a cathode-ray tube) that moves from left to right across the screen. The signal voltage moves the beam up and down while it travels from left to right, tracing the waveform and displaying it on-screen. Luminous phosphor on the back side of the screen glows where the beam hits it, displaying the waveform.

The cathode-ray tube(CRT) limits an analog oscilloscopes usage because at low frequencies, the signal is difficult to distinguish as an actual waveform. The Electron beam appears as a slow-moving dot on the screen. The CRT is also limited when the signal frequency exceeds its writing speed. If the oscilloscope can display a maximum frequency of 1 GHz, and the signal speed is 1.3 GHz, the display will be too dim to read.

Many analog oscilloscopes have controls that adjust the focus and intensity, creating clear, legible displays. Compared to digital oscilloscopes, analog oscilloscopes are preferred for displaying rapidly varying signals as they occur in real time. Since the phosphor display glows brighter wherever there are more frequent signal features, designers also easily distinguish details by observing the brightness intensity levels.

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