Measurement of very small signals can be challenging as the ability to view small signals is impacted not only by the noise of the scope, but also by scope settings and probing. Part I of this two-part series presented three techniques that can help your scope see smaller signals than you've previously seen with it. In Part 2, Agilent Technologies discusses four other methods that are applicable.
4. Use math functions such as magnify to vertically zoom
Once you’ve mastered using as much of the scope’s ADC bits as possible, the next challenge is to zoom in on the event of interest. In the case of signals with high dynamic range, a helpful technique is to create a function to show magnification of the portion of the waveform that is of interest.
Nearly all of today’s scopes come equipped with one or more math functions, or allow zoom windows where the zoom window includes both vertical and horizontal scaling independent of the main window.
For example, to zoom using a function, assign a function to magnify channel 1 of the scope. The user can change the position and scaling of the magnify function as shown in figure 4. This allows the main window to show the entire waveform, and the magnify function to zoom in on the area of interest. The math function (zoom) won’t have any better resolution than what the scope produced with the channel waveform, but you can see detail by zooming that would have been impossible to see when the full waveform was displayed.
Figure 4: In this example with an Infinium DSO9104A, the user has zoomed on a small portion of the channel waveform to allow viewing of a detail impossible to see on the original waveform. Infiniium scopes have 16 available functions enabling zooming of up to 16 areas of interestClick on image to enlarge