Power your measuring instrument with the signal you're measuring! Simply make two connections (the "positive" and "negative" leads of your input signal) and your new C&D "self-powered" meter is fully operational – with absolutely no external components or auxiliary power supplies required.
Perform dozens of everyday measurements easier than you ever thought possible. Measure the voltage at a standard USA-style wall outlet simply by "plugging in" an ac line monitor. Monitor the 400Hz frequency of an aircraft power generator without worrying about "proper" grounding.