What Is the Difference Between a Digital Oscilloscope and an Analog Oscilloscope?

The oscilloscope has been a mainstay instrument during the past 50 years for the tv technician all the way to an aerospace engineer. It is probably the most commonly used electronic instrument in the field of electronics circuit design, testing and troubleshooting. Rightfully so, might I add. It has the ability to graphically show the waveform, magnitude and time base of electrical signals on the display screen. Further, it can be calibrated such that the magnitude and frequency can be accurately observed. Further, many if not most of them have more than one input thus allowing for two or more signals to be viewed at the same time.

It is, therefore, a valuable and useful tool for those wanting to observe in real time the function and operation of electronic circuits. Since an electronic circuits operation is usually not visual (Oh, how many electronic students have wished that there was a visual feature to their circuit laying on the lab bench!) the ‘scope becomes a window into its operation. From a simple audio amplifier or oscillator to the video signals inside a television receiver or the output of a broadcast transmitter or heart monitor in the hospital the oscilloscope becomes a universal window for the engineer or lab technician.

The first few decades of oscilloscope designs were based on analog amplifier circuits that brought the amplitude of the signal to be viewed to the level sufficient to drive the deflection plates of the cathode ray tube in the oscilloscope. The oscilloscope had built into its circuit a saw-tooth waveform which moved the beam of the CRT from one side to the other and quickly returned it for another scan. The vertical deflection becomes the analog of the input signal. Via this mechanism the signal under test is now traced onto the CRT screen making it possible to view the symbolic representation of the electronic signal from the device under test.

Then, along came the world of digital electronic circuits. They are called flip-flops, logic gates, accumulators, counters, comparitors, sample and hold, binary counters and so on; you can get the picture. This new world of electronic circuits placed unique requirement on the visual function of the oscilloscope. Now it must be able to trigger at the exact time of a digital event. And, it must be able to show what happens to other parts of the circuit when a digital event happens – which may or may not be repetitive. Therefore, the development of triggering systems which can cause the scope to sweep only at the instruction of the incoming pulse to do so. Further, it may be necessary to synch the horizontal sweep to the clock frequency of the digital system thus showing the digital switching events in relation to the clock since timing is usually of major importance to the engineer, tech or person doing such things and debugging a logic module.

It is no wonder the digital oscilloscope became a big box of electronic circuits itself in order to accomplish all that is necessary for its functionality. The digital oscilloscope quickly became very complicated requiring some of the best digital electronics experts in the field to design them and perfect their performance as digital equipment (especially including the PC) became more sophisticated, faster and exotic. It would be inconceivable, for example, for a computer engineer to do the design work without the use of a digital oscilloscope at hand.

A leading company in the field of digital measuring equipment is Tektronix located in Oregon, USA. They have a very long line of such instruments, related modules and upgrades, software and application programs for testing and measurements for products in the computer, communications, manufacturing, automotive, space, fuel, government and many other fields. These rather complicated instruments can range in price from $200 to $20,000 depending on what must done and how they are to be applied in a given system environment.

There are many other companies manufacturing digital oscilloscopes and related test and measurement products. If you are needing such an instrument in your work you may contact this writer for further advice on how to go about it.

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