Getting The Most Out Of Your Oscilloscope: Cursors and Parameters
Oscilloscopes give us a wealth of tools with which to view, measure, and analyze the performance of a circuit. Broadly speaking, two classes of such tools are cursors and parameter measurements. Taken on their own, both classes afford the user a great deal of capability. Put them together, though, and you can really start to gain deep insights into what's going on with a waveform.
Figure 1: Cursors (top) and parameter measurements (bottom) are both powerful tools in their own right
Once you've acquired a waveform, you can quickly apply some cursors (Figure 1, top) to help with measurements. There are three basic types:
- Voltage (Vertical) cursors are dashed lines that you move vertically on the grid to measure the voltage levels of a signal. When used on a FFT waveform, dBV values are measured.
- Time (Horizontal) cursors are dashed lines that you move horizontally on the grid to measure the time values of a signal. When used on a FFT waveform, frequency values are measured.
- Track (Horizontal) cursors are cross-hairs that you move horizontally along any channel waveform. Place them at desired locations along the time axis to read the signal’s voltage levels at the selected times.
There's quite a large selection of parameter measurements, depending on the options installed in your Teledyne LeCroy oscilloscope (Figure 3). You can view the entire list by selecting All Measure when you're choosing a parameter, or you can view them by various categories. If you don't want or need to see the parameter descriptions, there's a button to the bottom left of the dialogue box that lets you view them as icons. This lets you see more of them at a given time.
Let's take a closer look at parameter statistics for a moment. In the measurement control dialogue box, you can find options for turning on statistics and histicons. The parameter statistics, which are compiled for all instances of a measurement, include the last measured value, the mean of all measurements, minimum and maximum values, standard deviation, and the number of measurements.
In the example statistics table of Figure 4, we can see that 13 amplitude measurements were taken, which says that we acquired 13 waveforms. Note that there are 767 frequency and duty-cycle measurements, but 780 rise- and fall-time measurements, which might be an interesting detail. At the bottom of each parameter, the measurement list is the corresponding histicon, which gives you a thumbnail graphical representation of how the statistical data is changing over time.
What histicons are actually showing you is the distribution of the measurements. They show you graphically whether the measurements are grouped around a mean value and whether there are any outliers among them. If so, then you probably want to move into troubleshooting mode.
We'll continue looking at ways to get more out of your oscilloscope in upcoming posts.
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Hey Tony, I wonder if we'll ever get to know the full capabilities of our scopes, but thanks for sharing these tips. Great insight. One tip to keep in mind when using cursors to manually measure the parameters of a waveform is to display the waveform as large as possible on the screen. This will allow you to more accurately place the cursors, thereby giving you a more accurate measurements. You can use the markers to identify areas of interest you want to zoom into, and quickly move through the data. The R&S RTC1000 Digital Oscilloscope lets you set up to 8 time markers. Best regards, and keep the tips coming,