Oscilloscope Reading Reference Cheat Sheet

Key Facts

• Peak-to-peak voltage is found from $V_{pp} = \left(\text{vertical divisions}\right)\left(\text{volts/div}\right)$.
• For a centered sine wave, peak voltage is $V_p = \frac{V_{pp}}{2}$.
• For a sine wave, root mean square voltage is $V_{rms} = \frac{V_p}{\sqrt{2}} = \frac{V_{pp}}{2\sqrt{2}}$.
• The period of one full cycle is $T = \left(\text{horizontal divisions per cycle}\right)\left(\text{seconds/div}\right)$.
• Frequency is the reciprocal of period, so $f = \frac{1}{T}$.
• A horizontal time shift between matching points on two waves gives phase difference by $\phi = 360^{\circ}\frac{\Delta t}{T}$.
• DC offset is found from $V_{DC} = \left(\text{vertical displacement from center}\right)\left(\text{volts/div}\right)$.
• If the probe setting is $10\times$, the actual signal voltage is $V_{actual} = 10V_{displayed}$ unless the oscilloscope is correctly set for a $10\times$ probe.

Vocabulary

Oscilloscope

An instrument that displays voltage on the vertical axis and time on the horizontal axis.

Volts per division

The vertical scale setting that tells how many volts each large grid square represents.

Time base

The horizontal scale setting that tells how much time each large grid square represents.

Peak-to-peak voltage

The voltage difference from the highest point of a waveform to its lowest point, written as $V_{pp}$.

Trigger

A control that starts each sweep at a chosen voltage level so the waveform appears stable.

Phase difference

The fraction of a cycle by which one repeating signal leads or lags another, often measured in degrees.