Five Things to Look for in an Oscilloscope

A digital storage oscilloscope is absolutely necessary for anyone designing, building, or repairing electronic equipment because it enables you to see single-shot or high-speed repetitive signals across several channels and identify glitches and other transient events. Furthermore, an oscilloscope is useful for qualifying elements of a new design as well as isolating components with issues in systems needing repair.

When choosing an oscilloscope, most people focus solely on bandwidth, because they assume a faster oscilloscope is a better oscilloscope but, although bandwidth is undeniably important, you should also consider rise time, sample rate, triggering, waveform navigation/analysis, and the probes.

Accurate rise-time measurements are central to making accurate time-domain measurements. Rise times are especially important for viewing square waves and pulses; square waves are used for testing amplifier distortion and timing signals for various devices, and pulses represent discrete bits of information or glitches.

The next thing you should look for is a fast sample rate, which determines how much waveform detail your oscilloscope can capture. Speed is of utmost importance when capturing glitches. High sample rates improve resolution and allow you to view intermittent events. You should look for an oscilloscope with a sample rate of at least five times the highest frequency component in the circuit.

You should also look for versatile triggering. Every oscilloscope has edge triggering, and most have pulse width triggering as well. Advanced triggering capabilities can really save time and speed up the time to answer when you’re dealing with more complex signals. A wider range of trigger options — including A & B sequence, video, logic, and communications triggers — makes for a more versatile oscilloscope.

Another thing to look for when you’re choosing an oscilloscope is powerful waveform navigation and analysis. Searching for specific waveform errors can be challenging, but capabilities like mark speed and search drastically speed up the process of searching waveform errors. Other capabilities to keep an eye out for are pan and zoom, pause and play, and advanced search tools.

The last thing to look for in an oscilloscope is matching probes, because precision starts at the tip of the probe. The probe’s bandwidth needs to match the bandwidth of the oscilloscope and must not overload the device under test. Your probes are actually a part of the oscilloscope circuit and add resistive, capacitive, and inductive loading which alters the measurement. You should also invest in a range of probes — passive probes with high bandwidth and low loading are a great place to start. Current probes let the oscilloscope calculate apparent power, instantaneous power, true power, and phase. Logic, optical, and environmental are types of specialty probes.

George

George Leger has a Masters in Electrical Engineering from Stanford University, worked in private industry pioneering surface-mount technology and in government research labs for twenty years, published several papers on surface-mount technology, co-authored papers published in national symposiums on accelerator technology, was past president of SMTA and an adjunct professor at the community college level, holds a patent, and is a certified microchip design partner, serving as a consultant to many companies developing electronic circuits.

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