Thermal Cameras are now considered to be an essential tool utilized in many industries for evaluating operating conditions, machinery safety and personal safety. They are used to measure surface temperature and to define a differential temperature. The primary purpose is always safety. Whether it be a safe temperature range for instrumentation, bearings, electrical connections, an HVAC system, heat during a first responder visit or searching for an unknown personnel at night in the woods, safety is always the primary concern. Some of the primary industries where Thermal cameras are widely used include: Process Control, Predictive Maintenance and Building Diagnostics, Commercial, Industrial, General and First Responder Use. There are many variables to considered when discussing and choosing a Thermal Camera. Each application warrants its own individual consideration on what specifications and options are important to the user. Below are some important areas to consider when determining features and benefits for any Camera and its application.

Typical applications where Thermal Cameras assist in providing a solution to a possible existing or developing problem:

• Utilities - Transformers, Insulators, Hipots, Transmission Towers
• Electrical - Unbalanced Loads, Overloads, Wiring, Circuit Breakers, Motor Windings,
• Mechanical - Steam Traps, Couplings, Bearings, Valves,
• HVAC - Ducts, Furnaces, Seals, Roofing,
• Rotating or Machinery Equipment Maintenance
• Energy Audits
• Moisture & Water Damage Restoration
• Refractory Insulation
• Tank and Vessel Levels
• Preventative Maintenance
• Predictive Maintenance
• Energy Transportation

Many cameras have important built-in unique characteristics. Below are top features that you may want to consider when searching for a Thermal Camera that best fits your application.

• IR Resolution or Pixel Array
• Thermal Sensitivity NETD
• Temperature Range
• Temperature Accuracy
• Field Of View ( FOV )
• Refresh Rate ( measured in Hz )
• Focus Capability - Manual / Automatic
• Digital Display with Thermal Display
• Memory and Data Logging Capability
• Wi-Fi or Bluetooth Capability
• Lens Capability and Interchangeability
• Alarm Capability
• Emissivity Capability
• Voice Annotation
• Output Capability
• Flashlight or Laser Capability
• Enclosure IP and CAT Location Ratings
• Drop Test Capability

IR Resolution (Pixel Array)

Every Thermal Camera has a specification stating the pixel array. It is usually defined as a matrix….60X60, 120X120, 160X120, etc. Detector resolution is based on the pixel array that each camera contains. Using larger pixel arrays, i.e., 640X480, (as well as the lens “Field of View” selected and any special electronics added to the optical circuit), cameras can measure smaller targets at longer distances. The image would be sharper and in greater detail. All cameras display temperature gradient. As the pixel array increase in size, the average temperature measured in a given area becomes smaller. This increases the information gathered by the camera. Pixel size directly corresponds to the application being considered as well as information being gathered. The detector resolution is most important when choosing a Camera. Increased Resolution provides more accurate quantitative results and is very important when presenting and reviewing results. Please note that the lens you choose as well as the matrix of the array are important for temperature detail.

Thermal Sensitivity NETD

The standard measurement used in Thermal Imaging for sensitivity is called “Noise Equivalent Temperature Difference” or NETD. NETD is accepted as a standard industry acronym. This measurement is basically the measure of the smallest temperature range that the camera can detect and display. When considering Cameras to use, a lower NETD may offer increased visibility of temperature differentials which in turn emphasizes smaller temperature changes in viewed objects.

Sensitivity is commonly shown as deg C and mK (millikelvins). When shown in the product specifications,  the camera sensitivity is usually indicated at a calibrated temperature, i.e. the sensitivity may read: .10deg C @ 30 deg C target temperature (or ambient temperature). It should be noted that with lower sensitivity, there usually is an increase in accuracy of readings as well as an increase in the details in captured images. Whether there are increases in detail, product color variations, minor modifications on wall intersections or product detail specifics, a lower sensitivity is certainly an important factor you may want to consider. Below are two panel-board circuit-breaker images. These are not identical images, but are used to demonstrate the variety of results when using two different sensitivities.

Figure 3 - Image from camera with 4800 pixels and a sensitivity of .15 deg C (150 mK). The general temperature differential is shown, but the detail is not as complete.

Figure 4 - is an image from a camera with 307, 200 pixels and sensitivity of .04 (40 mK).

Please note that although the pixel difference gives an increase in sharpness and clarity, the sensitivity allows us to see all the specific temperature details including wiring. The choice of cameras and sensitivity is also only one of many other specifications to consider. Temperature range, pixel capability, application, pricing and many others may also heavily influence your buying decision.

Temperature Range

This is application specific and is dictated by where/how the thermal image camera is used. In other words, the temperature range will be dictated by the application chosen. The primary temperature range may vary since cameras may be used for a variety of applications. Your primary area of concern usually dictates the temperature range you need, but keep in mind that future testing and evaluation may require other temperature ranges. Your needs will dictate the preferred temperature range of the camera, but keep in mind a larger temperature range means greater versatility from one camera, rather than several cameras with varying ranges.

FOV - Field Of View

The FOV or “Field of View” is the area of the image that is measured and viewed on the imager screen. The lens has the greatest influence on the total view, but a larger pixel array (matrix) may provide greater detail in observed temperature gradients.

Refresh (Frame) Rate (Hz)

In industrial and commercial applications, refresh rate or frame rate tells you the number of times per second the image on your thermal camera's screen updates or refreshes itself. Rates are commonly listed as 9Hz. 30Hz or 60Hz. Cameras with these frame rates will automatically refresh the displayed image 9, 30, and 60 times per second, respectively. Higher frame rates are usually found on cameras with better resolution as well as cameras used for First Responder” applications involving motion. Capturing motion on thermal video and using video output are the two main reasons to consider a higher refresh rate. The choice is based on application.

The following images are representative of observations using a Thermal Camera.

Figure 5 - Liquid level in a tank

Figure 6 - Condition of fuses in a circuit

Figure 7 - Image from a camera with 60x60 pixel array, 3600 pixels.

Figure 8 - Same image from a camera with 640x480 pixel array, 307,200 pixels.

Figure 9 - 640X480 pixel array, 307,200 pixels.

Figure 10 - 640X480 pixel array, 307,200 pixels.

Digital Display w/ Thermal Display

There are many cameras that contain a digital display, (much like a digital camera), as well as a thermal display. This allows more information on site and problem areas to be captured. These cameras usually allow the operator to snap a digital picture as well as thermal one. Below are two examples of capturing both a Digital and Thermal image in one picture.

Figure 11 - demonstrates a possible problem with a plug that is being used.

Figure 12 - Heat distribution in the circuit breakers panel

Wi-Fi or Bluetooth Capability

If the results you desire include the dissemination of information to other instruments, such as a PC or a tablet device, there are cameras that incorporate the software and capability to transmit this information via Bluetooth or Wireless. This information will allow you to provide increased detail in your reports extremely easily.

Emissivity

Thermal Cameras do not use visible light, but measure the infrared energy, or thermal energy, radiated from a surface. Since surfaces do not behave in a standard manner by which energy is radiated, we use emissivity to adjust for surface and radiated energy. Emissivity is the ratio of energy radiated (invisible heat) by a material to the energy radiated by a black body at the same temperature. It is the only type of heat that can be used to measure the surface temperature of an object. Most Thermal cameras contain a circuit that allows adjustment to emissivity after images have been saved. Emissivity numbers range from 0.0 and 1.0. A surface with a value of 0.10, (typical for shiny copper), radiates a much smaller amount of energy than that of the human skin, with an emissivity of 0.98. A “Black Body” would have an emissivity of 1.0. When measuring temperature and not differential, emissivity is extremely important in order to measure as accurately as possible.

If reading specific temperature values is desired, choose a camera with an adjustable emissivity. If differential temperatures are desired, emissivity, although always important, is not as critical. This will offer the user an opportunity for accurate results. There are many tables available that define the emissivity for most materials that can be measured. Many products have internal emissivity tables and many camera images contain a variety of materials with different emissivity. The camera image below shows a photo of wiring connections with the relative temperature differentials. This allows the inspector or professional to understand the heat produced in various locations of the panel.

Other factors to consider when buying a thermal camera:

• Focus Capability - Manual / Automatic
• Digital/Thermal Display image blending (FLIR MSX & Fluke IR-Fusion)
• Memory and Data Logging Capability
• Lens Capability and Interchangeability
• Alarm Capability
• Voice Annotation
• Output Capability
• Flashlight or Laser Capability
• Enclosure IP and CAT Location Ratings
• Drop Test Capability

Thermal Imaging provides information on your system and application that otherwise would not be known and available until a problem becomes evident. A thermal camera is an important tool to use in evaluating conditions that are important in day to day operation. For complete product information and details on what product will provide the very best results based on your needs and application, please call and speak to one of our Certified Level I/II Thermographic Experts.