The Importance of Spatial Resolution in IR Thermography Temperature Measurement - Three Brief Case Studies

Many modern IR cameras have built-in cross-hairs that show the user the size of the spot being measured. One would think this would solve the problem of measurement error due to a target at too great a distance for its size and IR camera resolution. But in our haste as thermographers under pressure to get results, we often don't take the time to ensure sufficient target size, or we use a function such as the maximum temperature in a box that does not show whether the target is adequate for measurement. Or, we don't have adequate optics or IR camera resolution to get a good measurement of a distant target that just isn't quite large enough. Whether the measurement errors resulting from inadequate spatial resolution really matter depend on the magnitude of the error and the criticality of the target. In our study we found a critical problem on a substation transformer at 40% load that could certainly devolve into a major failure as the load increased to 100% with increasing demand.