Thermal imaging (infrared thermography) detects faults by making heat visible. Most developing failures — a loose electrical connection, an overloaded circuit, a failing bearing, a blocked cooling path — produce abnormal heat before they break. A thermal camera shows that heat as a coloured image, so a technician can find and fix the problem during a planned inspection instead of after an unplanned breakdown. It is the core tool of condition-based and predictive maintenance.
What thermal imaging finds
- Electrical: loose or corroded connections, overloaded phases, unbalanced loads, failing breakers and fuses, hot spots in switchgear.
- Mechanical: overheating motors and bearings, misaligned couplings, belt and pulley friction, gearbox problems.
- Process / building: blocked heat exchangers, insulation gaps, refractory damage, steam-trap faults, moisture and roof leaks.
The specs that matter
| Spec | What it controls |
|---|---|
| Resolution (detector pixels) | How much fine detail you can see — more pixels means clearer images and the ability to inspect from a safe distance. |
| Thermal sensitivity (NETD) | The smallest temperature difference the camera can distinguish. Lower (e.g. ≤ 60 mK) reveals subtle problems. |
| Temperature range | Must cover the equipment you inspect, from cold rooms to hot process equipment. |
| Focus | An out-of-focus thermal image gives a wrong temperature — autofocus or good manual focus matters. |
How to read the results: comparison, not absolute numbers
The most reliable method is comparative thermography — compare a component to an identical one under the same load (for example, the three phases of a circuit). A phase running much hotter than its neighbours is the problem, regardless of the absolute temperature. This avoids the errors that come from emissivity and reflected temperature, which affect absolute readings.
Get the measurement right
- Inspect under normal or near-full load — faults often disappear at low load.
- Set emissivity correctly; shiny metal reflects and reads falsely cool.
- Keep a safe distance from energised equipment and follow your electrical safety procedures.
- Document the hot spot, the load at the time, and a reference image for trending.
Build it into a programme
One-off scans find problems; a routine thermal inspection programme prevents them. Establish baselines, inspect critical assets on a schedule, and trend the results so you can see a connection slowly degrading. Unitest Instruments supplies Fluke thermal cameras for every level — from handheld troubleshooting to high-resolution expert models — and can also carry out the inspection for you as a service.