If you did need to probe AC using the reference clip you need an isolation transformer for your scope. There are bigger implications when probing a board powered from mains which [Dave Jones] does ...

In short, [Christer] needed a high-frequency active differential oscilloscope probe, and they’re not cheap. So he built one himself. With some minor tweaking on the input damping resistors ...

When debugging your space electronics using an oscilloscope, many different measurement types are now possible, e.g., voltages, currents, power rails, digital logic, EMC, optical, TDR, and high ...