WHAT IS INFRARED THERMOGRAPHY
Infrared Thermography is the technique for producing an image of invisible infrared light emitted by objects.
As the relationship between infrared radiation and temperature is proportional, this result is displayed on an infra red camera using the visible spectrum of light to determine the differences in temperature.



Thermal image of a house


HOW DO INFRARED CAMERAS WORK?
All objects emit infrared radiation as a function of their temperature.  Infrared energy is generated by the movement of particles within the material.  The higher the temperature of an object, the more the movement and hence the more infrared energy is emitted. This is the energy detected by infrared cameras. The cameras do not see temperatures, they detect thermal radiation.
Most typical types of thermography cameras resemble a typical camcorder and produce a live picture of heat radiation.
 An image produced by an infrared camera is called a thermogram or sometimes a thermograph.

WHAT AM I SEEING ON AN INFRARED IMAGE?
The infrared camera captures the radiosity of the surface or target it is viewing. Radiosity is the infrared energy coming from a target affected by the atmosphere. It consists of emitted, reflected and sometimes transmitted infrared energy. The colours on an infrared image vary due to variations in radiosity. The radiosity can vary due to the temperature, emissivity and reflected energy variations.



Moisture leak inside a house


WHAT ARE THE BENEFITS OF USING AN INFRARED CAMERA?
Infrared thermography is a valuable and versatile tool suited to many applications. New and innovative ways of using the technology are being developed every day.
For Building and Heat loss inspection, infrared cameras are a versatile tool.
Even though they DO NOT measure moisture, there is however a close relationship between surface temperature and the detection of moisture. Colder areas can often indicate the presence of moisture or leaks.
Their prime use is to scan large and difficult to access areas quickly, highlighting possible areas for further checking.
Thermal Imaging is particularly useful in determining dew point problems, as well as air leakage and insulation issues
Cameras can detect problems quickly and non invasively.
For Electrical, Manufacturing and Industrial work, thermal imaging can provide vital cost effective maintenance solutions by indicating if electrical systems are overheating, mechanical parts are not operating efficiently and ventilation and air conditioning systems are performing poorly.



Hot fuse in a fuse box


INFRARED DETECTORS, PIXELS AND THERMAL SENSITIVITY
Most infrared thermal cameras available in the low to medium bracket ($5000 to $50,000) use FPA uncooled microbolometer detectors. These detectors collect long wave infrared radiation, usually between 7.5 and 13 μm. These type of detectors are low in cost, compact in size and economical on batteries when compared to other varieties of detectors.
The most common cameras have a pixel detector count of 160 x 120, however higher resolution models are available with
320 x 240 or 384 x 288 pixels.
The more pixels a detector has, the smaller the individual spot measuring size. When combined with a low thermal sensitivity (typically 0.1°C to 0.08°C), this increases the image quality and resolution.

REAL TIME REFRESH RATE & VIDEO
Frame rate, or refresh rate, is the measurement of the frequency (rate) at which an imaging device produces unique consecutive images called frames. This is most often expressed in progressive-scan monitors as hertz (Hz).
Many infrared cameras available on the market have a inadequate refresh rate which can range from anything as low as
6 to 14 Hz.  In some cases, the refresh rate specification is not listed on brochures or websites, or it is written in the accompanying small print.
Due to laws and regulations, some models are restricted to a slow refresh rate of only 7/9 Hz.
Commonly, infrared cameras with a “REAL TIME” refresh rate of 50/60 Hz are being used as they can provide sharp and smooth images at all times even with fast scanning movement and operation.
Some of the latest models on the market can record video in PAL or NTSC formats in real time.

FUSION TECHNOLOGY
Fusion is a function that allows the user to display a part of digital photo as an infrared image.
For example, you can set the camera to display all areas of the image that has a certain temperature in infrared, while all other areas will be displayed as a digital photo.
Fusion helps thermographers isolate problems, better identify and report suspect components and enable the repair to be done right the first time.

EMISSIVITY
Emissivity is the ratio of energy radiated by a particular material compared to the energy radiated by a black body at the same temperature. It is a measure of a material's ability to radiate absorbed energy.
For example, a high polished mirror has a low emissivity while a duller and blacker surface has a high emissivity. If you point an infrared camera at a mirror or glass window, you will see a reflection of yourself. This is the reflected energy being displayed.



Underfloor heating in a bathroom


COMMON INFRARED THERMOGRAPHY APPLICATIONS

ENERGY AND HEAT LOSS
Locate missing or damaged insulation
Thermal heat, air and energy loss inspections for buildings, apartments, offices, plants and facilities
Heated floor inspections for leaks and temperature distribution
Locate missing or damaged insulation
Evaluate the thermal performance of retrofitted properties and remedial repairs

BUILDING INSPECTION
Pre Purchase house inspections
Leaky Homes and Buildings
Internal and external leak detection and evaluation of walls, flat roof profiles
Multi story apartment inspection
Locate and identify mould growth areas in building structures
Locate moisture and delaminations in marine construction

ELECTRICAL & UTILITIES
Fuse box, wire loom and circuit board inspection and maintenance
Thermal mapping of pipes and semiconductor devices
Heat ventilation air conditioning equipment evaluation
Electrical motor inspections
Small scale power generation inspections
Substation Electrical inspections including switchgear, breakers, transformers and capacitor banks.

MANUFACTURING AND INDUSTRIAL
Boiler operation and maintenance
Inspect burners for flame impingement and burner management
Power Plant boiler flue gas leak detection
Mechanical bearing inspections
Cold Storage cooling losses.
Detect insulation leaks in refrigeration and cooling equipment
Steam Turbine and Hydroelectric Generators
Locate non uniform densities in hot mix asphalt paving

OTHER COMMON APPLICATIONS
Veterinary for Equine (horse) injury examination, stress fractures, lameness
Medical sports injuries evaluation, and therapy progress
Motor racing suspension, brake and engine systems evaluation for performance and cooling efficiencies
Food processing



Segments of this text are taken from the Flir IR Thermography Primer, by Flir Systems Co.Ltd 2008.