The following PDF document shows how to use a multimeter to measure current or voltage in a KidWind setup. Two multimeters are needed to measure current and voltage at the same time.
A multimeter is an inexpensive way to measure voltage and current. Note that it will only give you a live readout, and does not record changes over time. An easier way to make the same measurements is to use the Go Direct® Energy Sensor (GDX-NRG).