 Oscilloscope Frequency Measurements The oscilloscope displays waveforms on a graph that shows the shape, voltage, and frequency of an electrical signal. When it displays a sine wave, the scope is capable of measuring its frequency by using the graph on the screen and the seconds per division control located in the horizontal section of the oscilloscope face. The display screen below consists of a grid with vertical and horizontal lines. When reading frequencies, the horizontal space between the vertical lines is used. The space between each line is called a division. The seconds per division control shown below is a rotary knob that adjusts the time that each horizontal division represents. The time is in seconds, milliseconds, or microseconds. Before making a frequency measurement, it is necessary to obtain a waveform of the sine wave on the display screen. To achieve the most accurate reading, it is recommended that one sine wave is spread across as much of the screen as possible. Step 1a. Adjust the horizontal position knob to place the waveform at the center of the screen. Step 1b. Now adjust the vertical position knob. Step 2. Adjust the volts per division knob to the appropriate setting. If the knob is at a setting that is too small, the following waveform may appear. By turning the volts per division knob clockwise, the waveform will get bigger. If the knob is at a setting that is too large, the following waveform may appear. By turning the volts per division knob counter-clockwise, the waveform will get smaller. Turn the seconds per division knob to obtain one sine wave on the screen. If the knob is at a setting that is too large, the following waveform may appear. Too many waves are displayed. By turning the seconds per division knob clockwise, the waveform will spread out. Setting too small. If the knob is at a setting that is too low, the following waveform may appear. Only a small portion of the waveform is being displayed. By turning the seconds per division knob counterclockwise, the waveform will converge. Frequency measurement. To make a frequency measurement, the following steps are required. Step 1. Count the number of horizontal divisions of one period, which is one complete sine wave. In this example, one cycle equals nine divisions. Step 2. Observe the setting at which the seconds per division knob is positioned. Here the knob is at the 0.2 millisecond position. Step 3. Multiply the seconds per division setting by the number of divisions over which one period is displayed on the screen. 0.2 milliseconds times nine equals 0.0018. Obtain the frequency using the following formula. Frequency equals 1 over 0.0018, which equals 555 Hertz. You have completed this activity, oscilloscope frequency measurements.