Measuring cup, graduated cylinder, anything that has volumetric markings to tell you how much liquid you have. Or if the liquid has a known density, you can weigh it and determine its volume from mass/density. (You just have to make sure your units are all the same scale--if you weigh in lbs. and have density in grams/cubic centimeters, you have to convert lbs. to grams before using the density equation.
I know the basics of how to find these values from a graph, but not sure how to prove that average voltage of half-wave rectifier is peak/pi and rms is peak/2. Same for full-wave rectifier where average is 2peak/pi.
The simplest converter is a full-wave diode bridge, which converts the incoming AC to a fixed DC voltage. This isn't useful in a DC drive, but works fine for AC variable frequency drive (VFD). Standard industrial drives - both AC and DC - use six rectifier devices to form a three-phase full-wave bridge. This type of converter is called a six-pulse design, because it draws current in six distinct pulses from the AC line.