Use a multimeter for stable electrical values
A multimeter is the first choice for resistance, diode-mode readings and stable DC voltage. It can confirm whether a rail exists, but it cannot show the shape or timing of a changing signal.
Use a DSO for waveforms
A digital storage oscilloscope shows clocks, PWM, reset pulses and data activity over time. Correct probe grounding, voltage range, time base and triggering are essential.
Use a DC supply with control
A bench supply can show current behavior and can help localise a short through controlled injection. The voltage and current limit must be appropriate for the rail.
Let the diagnostic question choose the tool
Ask what you need to know: a static level, a waveform, or current behavior. Selecting the tool from the question prevents misleading readings.
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This article provides an educational overview. Measurements and board work should be performed with appropriate safety, schematic context and supervised practice where needed.
