When a Hot Spot Isn’t a Fault: 5 Thermal Imaging Mistakes to Avoid
Thermal imaging has transformed the way maintenance teams, engineers and inspectors identify developing problems.
Within seconds, a thermal camera can reveal abnormal temperature patterns across electrical equipment, machinery, buildings and infrastructure, often long before a fault becomes visible to the naked eye.
But there is an important distinction between capturing a thermal image and correctly interpreting one.
A bright area on a thermogram does not automatically indicate a dangerous fault. Likewise, an apparently normal temperature reading does not necessarily mean that an asset is healthy.
Focus, emissivity, reflected energy, surface characteristics, camera resolution and inspection technique can all influence what the operator sees and, more importantly, the temperature values being reported.
Understanding these variables is what turns thermal imaging into professional thermography.
Here are five common mistakes that can significantly change the outcome of a thermal inspection.
1. Poor Focus Can Affect More Than Image Quality
Focus might seem like a basic camera setting, but in thermography it forms part of the measurement process.
A poorly focused thermal image can blur the boundaries of small components and spread thermal information across neighbouring pixels. This can make the hottest point appear cooler than it actually is and can make smaller anomalies difficult to identify.
For maintenance inspections, this matters.
An electrical connection, bearing, terminal or other small target may occupy only a limited number of detector pixels. If the target is out of focus, the camera may not capture the temperature information accurately enough for reliable analysis.
And unlike an ordinary photograph, sharpening the image afterwards cannot recreate thermal measurement information that was never properly captured.
GoThermal Tip
Always confirm focus before recording or saving a thermogram.
Inspect the thermal image at the required working distance and ensure the component being measured is clearly resolved before relying on the reported temperature.
2. Incorrect Emissivity Can Produce a Very Convincing Wrong Answer
One of the most important concepts in infrared thermography is emissivity.
Different materials emit infrared radiation differently. Painted surfaces, plastics, insulation and oxidised metals generally behave very differently from polished aluminium, stainless steel or copper.
The thermal camera therefore needs the correct information about the target and surrounding conditions to calculate an accurate temperature.
If emissivity is incorrectly configured, the camera can display a temperature that appears highly precise while being significantly different from the true surface temperature.
This becomes especially important when inspecting:
- Electrical busbars
- Copper connections
- Stainless steel components
- Aluminium equipment
- Reflective machinery
- Polished metal surfaces
Professional thermography therefore requires more than simply placing a measurement cursor over the hottest-looking point.
The thermographer needs to understand the material being inspected, its surface condition and the environmental influences affecting the measurement.
GoThermal Tip
Never assume the default emissivity setting is correct for every target.
Reliable temperature measurement starts with understanding the surface being inspected.
3. The “Hot Spot” Could Actually Be a Reflection
One of the easiest thermal anomalies to misinterpret is reflected infrared energy.
Thermal cameras detect infrared radiation reaching their detectors. They do not automatically know whether that radiation originated from the target or was reflected from another source.
This becomes particularly important when examining smooth, shiny or low-emissivity materials.
A warm person standing nearby, hot machinery, sunlight, lighting, electrical equipment or another heat source can potentially create a reflected thermal pattern on the surface being inspected.
On the thermogram, that reflection may look surprisingly similar to a genuine hot spot.
This means that the hottest-looking area in an image does not automatically represent overheating equipment.
A trained thermographer will consider the wider environment and ask:
- Does the thermal pattern make sense for this component?
- Does the apparent anomaly move when the camera position changes?
- Could another heat source be reflected in the surface?
- Is the target highly reflective?
- Does the suspected fault correspond with how the equipment operates?
Changing the viewing angle can often provide valuable information when investigating a possible reflection.
GoThermal Tip
Do not diagnose a fault based purely on colour.
A thermal anomaly should make sense physically as well as visually.
4. Shiny Metal Can Hide a Serious Temperature Difference
Electrical inspections frequently involve copper, aluminium and other metallic surfaces, and these can be particularly challenging to measure accurately.
Bare polished metal generally has low emissivity and high reflectivity.
As a result, measuring directly from the metal surface may produce a temperature difference that appears relatively insignificant even when a more serious thermal condition exists.
This can have major consequences when maintenance decisions are based on temperature severity.
A connection that appears only slightly warmer than neighbouring components may be classified as low priority when the actual temperature difference is substantially greater.
Professional thermographers may therefore use appropriate measurement techniques or known high-emissivity reference surfaces where suitable and safe to obtain more representative temperature information.
The important point is that a small apparent temperature difference does not always indicate a small problem.
Sometimes the limitation lies in how the temperature is being measured.
GoThermal Tip
When dealing with low-emissivity surfaces, treat the displayed temperature with caution and consider whether the measurement technique is appropriate for the material.
5. Using the Wrong Thermal Camera or Lens Can Hide the Fault
Even excellent inspection technique cannot recover detail that the thermal camera never captured.
Thermal cameras vary significantly in:
- Infrared detector resolution
- Thermal sensitivity
- Measurement accuracy
- Lens options
- Field of view
- Focusing capability
- Temperature measurement range
The appropriate camera therefore depends on what needs to be inspected.
A wide-angle lens may be ideal for examining a large electrical panel or building area from a relatively short distance.
A telephoto lens may be more appropriate when the target is small or must be inspected from further away.
Similarly, a higher-resolution detector can provide substantially more thermal detail when examining smaller components, distant infrastructure or complex industrial systems.
One of the most important questions before starting an inspection is therefore:
Can the camera resolve the target accurately from the distance at which the inspection will be performed?
Simply seeing the component on screen does not necessarily mean there are enough detector pixels covering the target for dependable temperature measurement.
GoThermal Tip
Choose the thermal camera, lens and inspection distance according to the smallest target you need to measure, rather than simply the overall size of the scene.
Thermal Imaging Shows the Evidence. Thermography Provides the Diagnosis.
Modern thermal cameras are remarkably powerful inspection tools.
They can help maintenance teams identify abnormal heat patterns, electrical problems, mechanical deterioration, insulation deficiencies and other conditions before they develop into expensive failures.
But the camera itself cannot determine the cause of every thermal anomaly.
That requires understanding:
- Infrared radiation
- Heat transfer
- Emissivity and reflectivity
- Environmental conditions
- Equipment operation
- Measurement limitations
- Inspection methodology
- Thermal image interpretation
The real value of thermography therefore comes from combining professional thermal imaging equipment with correctly trained operators.
A thermal camera makes temperature patterns visible.
A thermographer determines what those patterns actually mean.
Build Better Thermography Skills with GoThermal
GoThermal provides professional thermography training in partnership with the Infrared Training Center (ITC), covering both introductory and advanced thermographic inspection principles.
Training options include:
- Introduction to Thermography
- ITC Category I Thermography Certification
- ITC Category II Thermography Certification
- ITC Category III Thermography Certification
- Classroom training
- Online training
- On-site company training
Participants learn how to operate thermal cameras correctly, understand temperature measurement, identify potential measurement errors, interpret thermal anomalies and produce reliable inspection findings.
Professional Thermographic Inspection Services
For companies that require professional condition monitoring, electrical inspection, preventive maintenance or risk assessment, GoThermal also provides thermographic inspection services conducted under the supervision of certified thermography professionals.
Using professional FLIR thermal imaging technology, GoThermal helps organisations identify developing faults, improve asset reliability and reduce the risk of unexpected equipment failure.
Need Help with Thermal Imaging?
Whether you need a FLIR thermal imaging camera, professional thermography training or a thermographic inspection, the GoThermal team can help you select the right solution for your application.
Contact GoThermal to discuss your thermal imaging requirements.