How to Measure Voltage with an Oscilloscope

Oscilloscopes help you visualize your electrical signal. At their core, oscilloscopes display a plot of voltage vs. time for one or more signals. This voltage vs. time graph is often called a “waveform.” This waveform is displayed by connecting a particular signal on the device under test (DUT) to the oscilloscope using a probe. The probe tip is connected to the signal and the grounding clip is connected to a reliable grounding point. Measuring the voltage with your oscilloscope provides basic information about the signal, however oscilloscopes often offer many more advanced tools to further analyze your signal. Understanding how to measure voltage with an oscilloscope is the first step to uncovering the powerful measurement capability your oscilloscope offers.

Getting Started: Oscilloscope Voltage Measurement

Step 1: Turn on your oscilloscope and push the “Default Setup” front panel key.

Step 2: Plug in a probe to Channel 1. Don’t worry too much about the type of probe at this point, but if you have one with a clip or other mechanism that prevents you from having to hold it to a wire, it’ll make your life easier. Below is a basic passive probe that’s great for getting started!

Step 3: Find a reliable grounding point and connect the ground clip to it.
Step 4: Connect the probe tip to the signal that you’d like to measure.
Step 5: The oscilloscope is now sampling your signal’s voltage and displaying it as it changes over time. If you don’t see the complete signal on screen, press the “Auto Scale” front panel key to center and scale your waveform.
Step 6: Use the vertical and horizontal knobs to further adjust how the signal is displayed. These knobs will help you zoom in and out as well as shift the signal right, left, up, and down. To get the best measurement, make sure your signal is spanning most of the vertical scale.

Step 7: The most basic way to calculate voltage is to count the number of divisions from top to bottom of the signal and multiply this by the vertical scale (volts/division). Note that the divisions are also labeled in volts on the Y-axis so you can easily calculate the voltage of your signal using these labels.

Many oscilloscopes have features that eliminate the need for counting division marks. Try one of these methods to more quickly measure voltage with an oscilloscope.
• Use on screen cursors to take a voltage measurement between two points (top and bottom of the waveform)
• Use voltage peak-to-peak measurement
• Use a built-in DVM

Learn more about oscilloscopes
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