The History of Oscilloscopes

Oscilloscopes are a modern tool used to measure the voltage, the amplitude, and the frequency of a variable electric charge. It produces what is called a 'waveform,' which is typically voltage over time, a graph that looks like a wave. Before the advent of the technology that makes this possible, a waveform graph had to be produced by hand, a long and extremely arduous process that involved taking copious electrical measurements separated by very little distance. Each of these measurements then had to be recorded by hand, eventually producing a graph. This process was first slightly automated by the French engineer Jules Francois Joubert, producing the first underpinning of a modern oscilloscope. He assembled a very precise machine that consisted of a galvanometer (a fairly simple tool used to measure electric current) with a probe, or contact point, that could be moved by a technician. Unfortunately, this still necessitated the recording of data by hand.

From here it was a simple jump to attaching the output of the galvanometer to a pen that moved across a drum of paper, drawing the measured waveform. At this point in the process the type of accuracy and precision seen by modern oscilloscopes was a long way off - the mechanical parts used in the early paper-drawn galvanometers were too slow to actually keep up with a changing electrical charge, and so the waveform had to be assembled piecemeal.

The next major step was the invention of cathode ray tubes, the precursor to digital display. By using a source of electrons and an electron-sensitive screen, cathode ray tubes could assemble and display a picture nearly instantaneously. By eliminating the need for slow moving mechanical parts, waveforms could be measured and displayed almost as quickly as the electrical charge itself changed.

This led, in 1946, to the invention of what can truly be called the first oscilloscope as we know them. The addition of the ability to easily change and moderate the time period over which voltages were collected allowed for the display of any part of a wave, including a level of detail heretofore unseen.

Of course, oscilloscopes have come a long way in the past 60 years, and modern machines have a number of incredible features, including the ability to carefully dictate when horizontal sweeping triggers occur, and the ability to very carefully fine-tune the number of horizontal sweeps that occur each second (easily in excess of 500,000!). These digital scopes also allow for the capture and storage of images or data right on the machine, making comparisons between two different waveforms possible and easy. Furthermore, by isolating specific parts of a waveform, circuitry components can be debugged and easily repaired. As the technology behind digital displays becomes more advanced and the displays themselves become cheaper to produce, oscilloscopes are quickly becoming a feature that no laboratory in the country is without, from introductory physics classes to any advanced electrical engineering laboratory to anyone that needs to test other electrical equipment.



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