Two ways to measure voltage with an oscilloscope

Direct measurement method for measuring DC voltage

Set the Y-axis input coupling switch to the "ground" position and the trigger mode switch to the "automatic" position so that the screen displays a horizontal scan line, which is the zero-level line.

Set the Y-axis input coupling switch to the "DC" position and add the voltage to be measured. At this time, the scan line produces a jump displacement H in the Y-axis direction. The measured voltage is the product of the "V/div" switch indication value and H.

The direct measurement method is simple and easy, but the error is large. The factors that cause the error include reading error, parallax and oscilloscope system error (attenuator, deflection system, oscilloscope tube edge effect).

Comparative measurement method

The comparison measurement method is to compare a known standard voltage waveform with the voltage waveform to obtain the measured voltage value.

Input the measured voltage Vx into the Y-axis channel of the oscilloscope, adjust the Y-axis sensitivity selection switch "V/div" and its fine-tuning knob so that the fluorescent screen displays a height Hx that is easy to measure and make a record, and keep the position of the "V/div" switch and fine-tuning knob unchanged.

Remove the voltage to be measured, input a known adjustable standard voltage Vs into the Y-axis, and adjust the output amplitude of the standard voltage so that it displays the same amplitude as the voltage to be measured.

At this time, the output amplitude of the standard voltage is equal to the amplitude of the voltage being measured. The comparison method for measuring voltage can avoid errors caused by the vertical system, thereby improving the measurement accuracy.

The above is an introduction to the two methods of measuring voltage using an oscilloscope. I hope you can compare and understand these two measurement methods.