PC Diagnostic Tools That Stop the Guesswork

Every item here replaces a guess with a measurement, and every one costs a fraction of the component someone would otherwise replace speculatively. The organising principle: it must answer one specific question, cost far less than the part it stops you buying, and require no interpretation to read.

This mirrors an approach the garage side of this site already takes — the cheapest useful thing you can own is frequently the one that tells you what is actually wrong.

A note on this collection: chosen on what each instrument settles, not on a set used here. See how we test.

An outlet tester

Three lights in a plug that report whether a socket is live, correctly wired and properly grounded.

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An ATX PSU tester

A device that loads the supply's connectors and reports each rail's voltage and the power-good signal.

The limits are covered honestly in testing a PSU before you replace anything else.

A USB power meter

An inline display showing voltage, current and the negotiated charging protocol.

A plug-in energy meter

A meter between the socket and the machine, recording consumption and peak draw.

A temperature sensor at the intake

A small thermometer reading the air the case is actually drawing.

What was deliberately left out

PC sensor panels. They display values free monitoring software already reads, via a background service, on a second screen. That is a display product rather than a diagnostic one, and it is described that way in PC temperature displays.

A multimeter. Capable of most of these jobs and requiring knowledge to use correctly around mains and live connectors. It is the right tool for someone already comfortable with it, and this list is for instruments that need no interpretation. The automotive side covers choosing one in the multimeter drain test.

HDMI signal testers. Genuinely useful for installed cable runs and overkill for one cable at a desk that can simply be swapped for a known-good one.

Software benchmarks. Free, useful and not instruments — they measure the machine's output rather than the conditions it is working in, which is the gap this list exists to close.