Digital Oscilloscopes
(364)It’s hard to imagine an electronic engineer who hasn’t come across an oscilloscope. Oscilloscopes are multifunctional and precise measuring instruments, which are now almost exclusively offered in a digital version. In the last few decades, many affordable models appeared on the market (these are most often dedicated to hobbyists, amateurs and apprentices). Having in mind that the TME offer is directed not only to experienced professionals, below we present an overview of digital oscilloscopes, focusing on their most important functions and applications.
Who uses oscilloscopes?
Oscilloscopes are among the most important measuring instruments, so the answer to this question would be: everyone who works with electronics. An oscilloscope allows you to observe voltage variations over time, which in turn makes it possible to analyse the operation of electrical and electronic circuits (such as power supplies and converters), check the operation of prototypes, conduct research, as well as teach the elementary laws of physics. In the field of RF engineering, which has more and more applications as wireless communication methods develop, it is practically impossible to work without an oscilloscope, as it helps to obtain the correct operating parameters of transmitters and receivers. In the case of digital electronics, oscilloscopes have fewer applications, as they are mainly used for interference detection, the checking of PWM signals and the operation of A/D and D/A converters. However, it should also be noted that the range of basic functionalities of oscilloscopes is constantly expanding, making them useful also in the field of analysis of communication protocols, etc
The difference between analogue and digital oscilloscopes
There are not many electronic engineers who still use analogue oscilloscopes (usually they do so because of their habits and costs), but we should remember that for decades they were the only available option. In short, their operation was based on processing and amplifying electrical signals, so that with the use of electromagnets they could curve a beam of electrons aimed at the screen. Current changes in the electromagnet coils (cyclical for the horizontal axis and dependent on the input voltage for the vertical axis) caused movement of the point where the electrons fell on the surface of the CRT. By adjusting the frequency with which the horizontal coordinate of the point changed to the frequency of the signal, a clear graph of voltage changes over a given period of time could be observed on the screen. In the case of digital oscilloscopes, as the name implies, measurements are made using analogue-to-digital converters, and the acquired data are stored in memory and presented on the screen, not directly but through software.
Advantages and functions of digital oscilloscopes
Since digital oscilloscopes store the measured results in the form of data, we can process them through software and by means of logic circuits. This allows to manufacture devices with a wide measuring range and perform a detailed analysis of the acquired values. Such studies are conducted by means of certain functionalities:
Saving and viewing the voltage graph
In contrast to analogue devices, digital oscilloscopes can produce the graph of even a single pulse, as the measured signal doesn’t have to be stretched over time. Still, voltage values can also be observed in real time, while the software automatically provides extremes and adjusts the sampling period. It is also possible to zoom in on selected portions of the graph and adjust its scale separately for each channel.
Measurement and analysis functions
The basic functions of digital oscilloscopes allow them to measure voltages and frequencies, as well as perform mathematical operations on selected values and curves, which enables you to verify phases and clock or PWM signals . It is also common for these devices to have the FFT (Fast Fourier Transform) function, thanks to which the oscilloscope can act as a spectrum analyser (so it can, among other things, identify interference, noise and other signals over a wide frequency spectrum).
Trigger function options
Digital oscilloscopes give the user a wide range of options in terms of trigger settings, i.e. determining the conditions under which measuring will be started. The choices in this function include: exceeding the current level, pulse, detection of a falling or rising edge, and even the curvature. The devices are also equipped with a “delay” or “dead” period/time control, a feature called Holdoff control. Owing to such design, the oscilloscope can be used to observe specific waveform fragments, anomalies, and even to monitor serial communication lines.
Connectivity and data transmission
In order to aggregate and analyse large amounts of data, special computer software is often used. To facilitate the import of data from the oscilloscope, such devices are equipped with standard communication interfaces (USB, Ethernet and sometimes even Wi-Fi) . Thanks to this, you can download information as well as observe measurements in real time or even control the oscilloscope remotely. Such improvements are especially useful in laboratory research and at the stage of prototyping – particularly if they are carried out by teams of engineers, where sharing the work results is one of the most important aspects.
Probes and accessories
Specialist probes, which can be used to examine different values and operation of energy sources and signals, extend the range of applications of an oscilloscope. They include: passive (typical) probes, with a damping factor switch (i.e., with a voltage divider that limits sensitivity to noise), current probes (for recording changes in current), differential probes (used primarily for measuring high voltage values in power lines), and active probes (which can provide additional functionalities or extend the range of tested frequencies).
Software-based interface
The detailed interface of digital oscilloscopes, which not only broadens the range of their applications but also makes using them easier, is definitely a huge advantage. First, the relatively high-resolution screen makes it possible to display detailed information, as well as ‘hints’ and explanations of individual functions. Secondly, the use of touchscreens makes operating the oscilloscope almost intuitive. Thirdly, the user can adapt the operation of the device to their needs, for example, by saving the settings for frequently repeated measurements. Finally, it should also be noted that manufacturers often offer software patches for their oscilloscopes, improving their functionality and accuracy ‒ separate firmware packages are sometimes available for an additional fee and offer a significant expansion of the devices' capabilities.
Additional functions
New models of oscilloscopes are in fact laboratory instruments, whose capabilities far exceed simple testing. They often have built-in function generators with different waveforms, can decode signals of communication protocols, and can even serve as logic analysers (by recording the state of several lines over a relatively long period of time). These functions are especially useful when it comes to working with digital electronics.
Applications of digital oscilloscopes
Thanks to the functions described above, oscilloscopes can be used in many fields ‒ they have also become more affordable devices. What is more, even the most basic models are characterised by high operating frequency, good resolution and precision. As a result, both the extent of applications of oscilloscopes and the target group of their users have expanded.
Testing and maintenance of electronic circuits
Oscilloscopes are a part of an essential equipment when it comes to design and repair of electronic devices. There, it is crucial to obtain the correct values of voltage, current and frequency, provided in the project. Using an oscilloscope, you can detect deviations from correct operating parameters, identify faults or inaccurate assumptions made at the design stage.
Analysis of telecommunication signals
The communication and telecommunication standards strictly determine the acceptable specifications for the operation of equipment and components. In the case of interference or even errors, an oscilloscope enables you to detect the cause of such occurrences – by locating the source of interference, measuring the times with which signals are transmitted, the proper values of voltages between lines , etc.
Quality of power supply
Another important field of application for digital oscilloscopes is power supply and power quality testing. These are typical operations, performed as part of maintenance and inspection of industrial plants, especially machinery parks, where automated systems are implemented. In this field, oscilloscopes are used to check voltages in power supply lines or inverter outputs, as well as currents supplied to individual components ‒ to ensure optimal system operation and the safety of machine operators.
Development and research
Since digital oscilloscopes are not only multifunctional but also offer high sensitivity, they are commonly used in laboratory research – in development centres and universities alike. Naturally, they are used in fields such as physics, electrical engineering, RF engineering, but also chemistry, astronomy and medicine – virtually any discipline in which electronic equipment starts to play a bigger role.
Education
Lastly, it is important to note that oscilloscopes are excellent educational tools. With their use, students can experimentally examine and ‘see’ the course of an electric current, which is difficult to illustrate otherwise and is often taught through pure theory, which does not always translate into satisfactory results.
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