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Recommended Resolutions
The following recommendations serve as a general guide only. Please speak to one of our qualified thermographers (hyperlinked to Contact Us page) before deciding what is appropriate for your application.
In general…
The smaller your target the more resolution you will need.
The greater the distance from your target, the more resolution you will need.
Accurate temperature measurement requires the correct spot size for the target and for measurement accuracy, the spot size must be smaller than target area.
It should be noted that it is impossible to compensate for incorrect spot size. Spot size must be appropriate at the time of measurement and/or at the time of image capture. When spot size is larger than the target, the imager will measure the target and the area beyond averaging the temperatures of both together. In some cases, this can produce temperature values that may be inaccurate by hundreds of degrees.
Low Voltage Distribution presents us with target sizes as small as 2.5mm (think about the smallest target you will need to measure). As such we need to plan our measurement capabilities on the lowest common denominator, and our spot size needs to be less than 2.5mm.
A common and acceptable resolution for this application is 160×120, which generally provides adequate measurement at 1 meter distance from a target this size. It may be possible to use a 120×120 resolution camera with an appropriate lens, although this resolution is quite low and not ideal for this application.
A professional thermographer would seek 320×240 resolution or higher for both measurement and aesthetic consistency. Typically a camera of professional resolution will allow us to measure the same target from a much greater distance, and the image quality overall is much higher allowing thermal patterns to be more easily observed.
High Voltage, Overhead Networks, Substations
With power transmission and distribution our greatest challenge is the safe working distance from our target. Usually these applications will require us to be several meters from our target 5, 10, 15, 20 meters, and in some cases our target size can be as small as 40mm (think about the smallest target you will need to measure). We generally would not consider resolutions less than 320×240 for this application and in some cases telephoto lenses will be required.
Building Sciences, Energy Loss, Moisture, Pest Management
This is a broad industry sector and the applications can range from quite simple to very demanding in terms of your equipment requirements. For most domestic applications 160×120 resolutions are sufficient. Where this resolution becomes a limitation is with larger objects or buildings (ie commercial buildings, roofing, car parks, multilevel construction), where greater areas and distances are involved and more resolution will be required.
From this thermographer’s perspective, a more important consideration is the Thermal Sensitivity, (hyperlinked to below) which is supported by the fact that most camera manufacturers will develop these models with the lowest sensitivity possible.
Mechanical and Rotating Equipment
Mechanical and Rotating Equipment such as pumps, motors, bearings, conveyor systems, hydraulics, etc are the least demanding in terms of resolution requirements. They are generally large in size, and we can get quite close in proximity (usually within a meter or two). As such most of these targets can be imaged with the lower resolution cameras, such as 120×120. In some cases, equipment may be placed in hard to reach locations (elevated) or protected by safety barriers and we may be forced to work at much greater distances. This will require higher resolutions and you will need to anticipate your access to equipment before selecting a camera.
Energy Loss, Refractory Integrity
The inspection of large vessels for energy loss or refractory/insulation integrity usually requires the use of high resolution cameras (ie greater than 320×240). This would include targets such as lagged pipelines, ductwork, steam pipes and traps, furnaces, ovens, boilers, chimney stacks / flues etc. In most cases we have to work at considerable distances from the target, and despite the object being quite large, often the target (area of interest) may be quite small. For example consider a large chimney stack. While the stack may be several meters in diameter, we may be trying to identify a missing insulation brick only centimeters in size. Cracks in vessels may only create very small localized temperature patterns which will require very high resolution.