Oscilloscope Controls & Measurements

Trigger controls: A triggering on your signal can help produce both a stable and usable display as well as enable you to synchronize the oscilloscope’s acquisition of the portion of the waveform you would like to view. The trigger controls let you implement the vertical trigger level, such as the voltage you would like the oscilloscope to trigger, in addition to choosing between various triggering capabilities. Let’s take a look at some common triggering types.

Edge triggering: The most popular triggering mode, edge triggering occurs as soon as the voltage exceeds a set threshold point. You have the choice of triggering on a falling or rising edge.

Glitch triggering: Glitch triggering lets you trigger on an event or pulse with a width greater than or less than a specific length of time, and this capability is quite useful for discovering random errors and glitches. Although these types of glitches can be difficult to spot when they don’t happen often, glitch triggering will help you catch such errors with ease.

Pulse-width triggering: Pulse-width triggering is remarkably similar to glitch triggering when you need to inspect certain pulse widths. Pulse-width triggering is, however, more generalized in that you can trigger on pulses of any specified width and choose the polarity — negative or positive — of the triggered pulses. Furthermore, you can set the horizontal position of the trigger, which allows you to see what happened before or after the trigger; for example, you can carry out a glitch trigger, discover the error, and analyze the what happened before the trigger to cause the glitch.

Your trigger event will appear in the screen’s middle if you have the horizontal delay set to zero; events occurring before the trigger event will appear on the left of the screen and events occurring after will show up on the right side. You can set the trigger’s coupling and set the input source on which to trigger as well. You won’t have to trigger on your signal all the time — you can trigger on a related signal instead.

Input controls: Most digital storage oscilloscopes have two or four analog channels each of which are numbered and have a dedicated on/off button. There is also sometimes a selection for specifying AC or DC coupling: the entire signal will be input when DC coupling is selected; AC coupling will block the DC component and center the waveform around zero volts (ground). What’s more, you can designate the probe impedance of each channel with a selection button. Oscilloscope input controls allow you to choose the type of sampling: real-time or equivalent-time sampling.
Nick Jakubowski

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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