Why your thermal camera cannot quite resolve that PCB hotspot

Separate detection from identification

A camera may show that an area is warm without separating the individual parts within it. Locating a warm cluster, identifying a component and measuring its peak surface temperature are different tasks.

At close range, a fixed-focus lens may leave a board blurred. Moving farther away restores focus but makes each component occupy fewer pixels. A macro accessory or adjustable-focus lens changes that trade-off, rather than simply adding more pixels.

Look at working distance and depth of field

SDG's P2 Pro review describes a much closer working distance with its macro lens than with the bare camera, alongside a shallow depth of field. These are observations from that review, not a promise for every unit or attachment.

Gough's P3 and TS001 articles compare practical focus and field-of-view differences on real targets. Look for a board in focus across the region you need, enough clearance for probes and a position that can be held steadily.

Make the board comparison repeatable

Start with a known, low-voltage board and a controlled power supply. Keep the load, time after power-on and airflow consistent. Match the palette and temperature scale if comparing cameras, and photograph the component locations in visible light.

An overlay can help you navigate, but close-range parallax may shift the visible and thermal images apart. Confirm component positions from the board itself rather than trusting the blended outline.

• Record supply voltage, current limit, load and elapsed time.
• Keep camera distance, focus and viewing angle consistent.
• Use a stable stand for close-focus work.
• Keep the original file and a labelled visible photograph.
• Confirm the suspected fault with electrical measurements.

A hotspot is a clue, not the verdict

A regulator or power transistor may be warm because it is doing its intended job. A thermal pattern alone does not prove a short, a damaged component or an unsafe condition.

Compare with expected operation and, where available, a known-good board. Recheck with appropriate electrical measurements. Mains-powered equipment introduces hazards beyond the camera: this low-voltage workflow is not an instruction to work on exposed live circuits.