 Oscilloscope phase shift measurements. When an AC voltage is applied to a series RC circuit, the voltage drops across the resistor and capacitor are not in phase. The number of degrees there out of phase is determined by the relative values of the components. To display the voltage waveforms across the resistor and capacitor below, two oscilloscope probes must be used. One channel of the scope is connected across the resistor. The second probe from the other scope channel is connected across the capacitor. A ground connection must be made at the bottom plate of the capacitor. Two waveforms that are out of phase, such as the ones below, will be displayed on the oscilloscope screen. To determine the phase difference in degrees of these two waveforms, follow these steps. Step one, move the coupling switches of both channels to the ground position. The scan line will appear. The scan line for channel one is in the reference position. Adjust the vertical position of the channel two scan line to the same position as the channel one scan line. Step two, place the coupling switches for channel one and channel two in the AC position. Step three, adjust the calibration knob to make the largest waveform the same size as the smaller one. Step four, count the number of spaces between the marks on the screen for one cycle. Here there are 41 spaces between the marks. Step five, to determine the number of degrees each space between the small marks equals, divide the following values. 360 degrees divided by 41 equals 8.78 degrees. So each space is rounded to 8.8 degrees. Step six, to determine how many degrees waveform one leads waveform two, count the number of small spaces between where the first sine wave crosses the horizontal reference line in the positive direction and where the second sine wave crosses the line in that direction. The number is four. Multiply the number of spaces by the degrees per space between the small marks. Four spaces times 8.8 degrees equals 35.2 degrees. The farthest waveform to the left that crosses the horizontal reference line in the upward direction leads the other waveform. You have completed this activity, oscilloscope phase shift measurements.