Oscilloscope Basics Revisited

An Oscilloscope? What is it? For a basic starting point, it shows the heartbeat of electronic devices. Oscilloscopes give insights into electronic devices and whether or not they are operating correctly, providing a user the ability to check signal health.

The signals of devices could be voltage or current. And the goal is to make sure those voltages or currents are oscillating at the right pace or frequency. We all know electronic signal glitches are bad, and an oscilloscope can help us find them. Being able to view the signals of an electronic devices allows a user to validate it is operating as expected. If a device is not operating properly, an oscilloscope can help diagnose the problem and correct it. Most electrical engineers, either need or already use an oscilloscope. This also applies to test engineers, students, or users who work in manufacturing, repair, research, or development.

The Basics of Oscilloscopes

In its most elementary understanding, an oscilloscope displays voltage versus time, with voltage on the vertical axis and time on the horizontal axis. This allows a user to review that a device’s signal is as expected, both in magnitude and frequency. A feature oscilloscopes provide is a visual representation of the signal, so a user can view any anomalies or distortion which may be occurring. But before a user can just jump in and test, there are some things to consider.

Just like cars, there a multitude of choices when looking for an oscilloscope. A user needs to boil it down to the right bandwidth, signal integrity, sample rate, and channel inputs. Also, an oscilloscope choice needs to be compatible with any applications and accessories that may be tested. The following is a basic list of features to consider when deciding on an oscilloscope:

Bandwidth – The range of frequencies an oscilloscope can measure accurately. Oscilloscope bandwidths can range from 20 MHz to 200 GHz.

Sample Rate – The number of reading samples an oscilloscope can take per second. The more samples per second, the more clearly and accurately defined is the display of a waveform.

Signal Integrity – In a nutshell, the oscilloscope’s accuracy of showing a waveform correctly. With a device under test, a user wants an accurate reading to save from wasting time troubleshooting for a root cause problem in a device when there isn’t actually a problem.

Channels – The number of inputs to the oscilloscope. Inputs can be analog or digital. Typically oscilloscopes have either 2 to 4 channels.

Probe Compatibility – A probe is a tool used to connect an oscilloscope to the device under test. Probe types include passive and active probes, each designed for specific uses. Oscilloscope and probes need to be compatible with specific tests.

Multiple Applications – Signal analysis, protocol decode, and compliance test software can reduce the time it takes to identify and capture errors in designs. Analysis software can help a user find and evaluate jitter, create eye diagrams, perform Fourier transforms, and even diagnose crosstalk. Protocol decoding software identifies digital packets of information, trigger on different packet occurrences, and identify possible protocol errors. No one oscilloscope is compatible with all applications.

Portability – Is a portable or bench-top unit more suited for a user’s applications? Both options work the same, but if a user needs to move an oscilloscope around to many locations or from bench to bench in a lab, then a portable handheld oscilloscope would be ideal.

Oscilloscopes Are Used For Multiple Applications

Basic testing usually requires an oscilloscope that has 50 to 200 MHz of bandwidth, a passive probe, and ample sample rate, signal integrity, and 2 to 4 channels.

In using a basic oscilloscope set up, a user can spot-check printed circuit boards (PCBs), power lines for noise, shorts, and I/Os (inputs and outputs) that are not functioning properly. Also different trigger modes can be used to search for runts, glitches, and timing errors. Signals and data will need to be captured to prove the quality of designs and manufacturing. A few basic oscilloscopes can even perform Bode or frequency and phase response analysis.

The multitude of uses for which an oscilloscope can be used shows it is a versatile and widely used instrument. Oscilloscopes are used by automotive technicians to diagnose electrical problems in cars. Schools at all levels take advantage of oscilloscopes to teach students about electronics. Oscilloscopes are used in many other applications: research, cell phone signals, military and aviation testing of radar communication systems, R&D departments to design and confirm new technologies, and compliance testing.

In sum, choosing an oscilloscope is not as difficult as it is made out to be – a user needs to know what applications need to be tested, and then match up an oscilloscope’s capabilities to the application.

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