How to Calculate DC Ripple Voltage

By Thomas James

One of the applications of rectifiers is in welding, where the rectifier is used to provide a polarized voltage.
i welding project image by leemarusa from

In electronics there are two types of current: alternating current and direct current. Rectifiers are used to change from an alternating current to a direct current. Rectifiers are imperfect, and there is usually a residual oscillation, or "ripple," in the signal output from the rectifier. You can calculate this ripple using the printout of an oscilloscope reading of the signal output from the rectifier.

Place the end of one of the voltage probes of your oscilloscope at the output to your rectifier. Place the other voltage probe to a ground. Observe that there is a slight "ripple" visible in the signal displayed on the oscilloscope screen.

Press the print key on your oscilloscope. Retrieve the printout.

Hold the multimeter current probe against the output of the rectifier. Make a note of the recorded value of the current.

Multiply the frequency of the ripple voltage by the capacitance of the rectifier and make a note of this value. The capacitance of the rectifier will be recorded in the rectifier data sheet.

Divide the current value noted in Step 3 by the product of the capacitance and the frequency noted in Step 4. The resultant value will be the peak-to-peak ripple voltage of your circuit.