Measuring sleep mode and standby mode currents drawn by low power, portable devices such as consumer products (cellular phones, tablets, laptops), industrial products (wireless transmitters, intrinsically safe instruments), and implantable medical devices (pacemakers, defibrillators, neurological stimulators) is essential to ensure that critical power consumption specifications are met.
These tests require precise low current measurements down to microamp levels, which requires not only good measurement techniques but also sensitive instrumentation with special capabilities for measuring very small load currents. However, specialized, sensitive instrumentation is costly and adds more complexity to the test circuit.
A readback power supply for both sourcing voltage and measuring current is one solution, but most conventional programmable power supplies (read more about DC power supplies) have a measuring resolution of only milliamps at best and, therefore, cannot be used for low current measurements.