Putting Probes in Perspective

Figure 1: Probe, cable, and oscilloscope form a system
that makes or breaks the accuracy of signal acquisitions

Few aspects of using an oscilloscope are as important as the probe: after all, the probe forms both the mechanical and electrical interfaces between the device under test (DUT) and the oscilloscope itself. To feed a signal into an oscilloscope, we're limited to a coaxial connection. Thus, we need a geometry transformer that picks up the signal of interest from the DUT and transfers it to the oscilloscope's coaxial connection.

Testing Techniques For Switch-Mode Power Supplies

Figure 1: A simplified schematic of
a switch-mode power supply circuit

On its journey from wall socket to the device being powered, power typically passes through a switch-mode power supply, where the AC signal is rectified into DC before it reaches the device. After that, the DC signal (often 5 V) is passed on to DC-DC converters on the device's PC board for feeding various voltages to branches of the device's power-delivery network. Let's look at some of the measurement techniques and considerations relative to testing switch-mode power supplies.