Oscilloscopes: The digital alternative: The digital scope's capability in measurement, transient capture, and data storage is a significant improvement over its analog counterpart

Abstract

As with its analog counterpart, the primary function of a digital oscilloscope is to graphically display the voltage and time characteristics of an analog waveform. The front panel controls are also very similar, including amplifier, triggering, sweep timing, and display. However, the digital oscilloscope not only acquires and displays analog signals, it also stores them in a solid state memory, and thereby offers many advantages to the user. The resolution and accuracy of an analog oscilloscope are restricted by screen size, phosphor characteristics, and the limitations of the human eye to a typical range of 2 or 3 percent. In contrast, many modern digital oscilloscopes offer a voltage resolution of one part in 4096, or the ability to detect a 0.25 mV change on a one-volt signal. Similarly, horizontal timing is significantly improved in a digital oscilloscope since the incoming signal is sampled at a rate determined by a crystal-controlled clock. Each sample is converted to a digital value and stored in memory, producing a digital image of the original waveform. This digital representation of the analog signal is extremely accurate, with the voltage and time coordinates of each point precisely known. Thus, although the image is reconverted to analog form for display, the reliance on CRT characteristics for measurement accuracy is completely avoided.