Question

1. Describe and discuss the concept of oscilloscope “triggering” and how it is implemented in modern oscilloscopes (i.e. how the oscilloscope WORKS internally, and not simply how to use the scope). Develop your description around a block diagram of the oscilloscope. Include “typical” internal oscilloscope signal waveforms. Work a description of the function of the oscilloscope “trigger” controls into your discussion. The use of one or more references, either those cited above or some found on your own, should be useful here. Be sure to properly cite sources of your information, figures, etc. Do not plagiarize!

2. Using precise engineering terminology and possibly with the aid of schematic diagrams and charts, describe, discuss, and explain the effect that the vertical amplifier COUPLING has on the performance of the oscilloscope. When is it appropriate to use AC coupling or DC coupling? Under what conditions might AC coupling introduce errors into a measurement? Under what conditions might DC coupling introduce errors into a measurement?

3. Contrast and compare the AUTO with the NORM triggering mode.

4. a. Define, discuss, and explain the differences between precision, accuracy, resolution, sensitivity, and range as they pertain to measurements or measuring instruments. Consult reference 2 or another suitable source. b. Give numerical examples of each, i.e. for each one give a hypothetical set of data and/or measurements taken by (or given for) a hypothetical instrument and show what analysis/interpretation must be done on the data/measurements to obtain the particular parameter. Then, give the resulting numerical value for that parameter.

Answer 1

1.

The trigger section controls the start event of the sweep. The trigger can be set to automatically restart after each sweep or it can be configured to respond to an internal or external event. The principal controls of this section will be the source and coupling selector switches. An external trigger input (EXT Input) and level adjustment will also be included.

Advanced Trigger

As waveforms, particularly the digital signals in both parallel and serial buses, have gotten more complex, the venerable edge trigger has become too limited to suffice as the sole means of acquisition. Continuing the photography analogy mentioned earlier, edge triggering simply doesn’t give the oscilloscope enough information about “where to stop” for the best pictures. Advanced triggers respond to more rigorously specified conditions in the incoming signal, making it easy to detect, for example, a pulse that is narrower than it should be. Such a condition would be impossible to detect with an edge trigger alone. Advanced trigger controls enable you to isolate specific events of interest. The Pinpoint trigger system gives you highly selectable control over the type event you are trying to capture. You can trigger on pulses defined by amplitude (such as runt or window); qualified by time (pulse width, glitch, slew rate, setup-andhold, and time-out); both amplitude and time using window triggering; or delineated by logic state or pattern (logic triggering). The intuitive user interface allows rapid setup of trigger parameters with wide flexibility in the test setup to maximize your productivity. The advanced trigger menu can be displayed by selecting the trigger setup menu item with a mouse or the oscilloscope’s touch screen or by pressing the ADVANCED button in the TRIGGER section of the front panel. Many oscilloscopes offer dual A-B triggering. The A (main) trigger is usually a full-featured system that incorporates advanced triggers, while the secondary B trigger is limited to edge-style detection. The A trigger acts as a qualifier. Its occurrence enables the B trigger to look for a defined voltage threshold.