A High precision power supply, like the Keithley 2280S and 2281S, is exactly like it sounds like. A power supply that can deliver voltage and current with less noise as well as superior resolution and step size. For instance, the 2280S and 2281S have less than 1 mV RMS noise. They can also measure low uA and tenths of uA currents with 10nA resolution. They can also capture narrow load current bursts as narrow as 140us and offer up to 6 ½ digit resolution.