In our first two oscilloscope projects, we examined the way to display a waveform on our oscilloscope so that we can visualize the “shape” of a voltage with respect to time. We can measure parameters that we may be interested in—amplitudes, frequencies, phase differences, and so on—directly from this display, since vertical and horizontal scales are provided on the display; however, most oscilloscopes provide tools which assist in the measurement process. This project will familiarize us with some of the most basic and common tools used to simplify the measurement process.
Please be aware that these tools are not a substitute for scrutinizing the waveform display itself! Measurement tools are intended to be used in conjunction with engineering insight into the circuit's behavior. When an oscilloscope displays a “measurement”, the tool may be making assumptions about the waveform which are not valid! Always perform at least a rough double-check of any displayed measurements against the waveform itself.
The tools introduced in this project are the measurements tool and the cursors. The measurements tool provides automated measurement of a number of common parameters. The cursors are generally used if a specific voltage or time measurement is desired, which needs to be customized by the user.
If you have completed the Oscilloscope Triggering project, and your circuit is still intact, you will be ready to begin this exercise. If you no longer have the circuit set up, check out and construct the circuit displayed to the right.
The measured value should appear in the list in the Measurements window. Check the value against the waveform shown in the display screen, to see if it makes sense. You can add additional measurements using the Add Measurement dialog box now. When you are done, close the Add Measurement dialog box.
Use the Measurement window to measure the maximum channel 2 voltage that you used cursors to measure in part B. Does the value in the Measurement window agree with the results you obtained with the cursor?