Many traditional DMMs lack the capabilities to measure dynamic behaviours, especially those found in the class of switch mode power supplies (SMPSs). An oscilloscope can help but many do not offer the resolution needed to correctly characterize the very low level ripple noise.
Many engineers use a Graphical Sampling Multimeter which can sample voltages down to 1µV or current down to 100pA sensitivity at 1µs intervals.
The attached application note illustrates how you can capture, view and characterize the dynamic ripple voltage on a DC-to-DC buck converter using Keithley’s Model 7½-Digit Graphical Sampling Multimeter.
You can digitize a variety of dynamic low level voltage and current waveforms with 18-bit accuracy at a 1Mega-sample per second sampling rate. Combining with the instrument’s multi-touch touchscreen interface technology, you can easily capture, view, and interact with both steady-state and dynamic signals from power supplies.