Things to consider before buying a thermal camera
What do you intend doing with your camera? Is your work going to be limited to electrical, or building, or are you looking for a camera that can be used in many different applications? Are you going to be working on high level projects? These are important questions to ask before buying. There are cameras that are made specifically for the building industry, but these usually have a limited temperature range, and may limit your future options.
If you are going to be working exclusively in building thermography, then a limited range may be enough. It will be unlikely that you will need a camera that is capable of measuring above 60 degrees C. If your application is going to be primarily electrical, then you will need the ability to measure higher temperatures, perhaps up to about 250 degrees. You must remember that you may come across components that are above this level, but will you really need to know how much above this level that they are? Some people may decide that for electrical, they will need a temperature measurement range up to about 500 degrees C, above this level is probably unnecessary. Refractory insulation and some mechanical applications may require higher temperature measurement capabilities, you need to consider if you require this or not. It is possible with some cameras to have extended ranges retro fitted to a camera. If you think that there is any possibility that you may need very high temperatures at some time in the future, then you should make sure you order a camera that can have this upgrade fitted afterwards.
Thermal sensitivity or NETD is a very important issue for some applications. The lower the number in a specification the better this value is. A very sensitive camera will allow you to see smaller temperature differences, this is particularly important for building thermography. Be careful with specifications, some camera manufactures will quote a value that is averaged over a number of frames. You should compare a value that is not averaged and make sure all the values are quoted for a scene of 30 degrees C, as some manufacturers measure this at 50 degrees C in order to get a fake result.
The current industry maximum for a portable camera is a 1024×768 detector, while at the lower end there are many cameras with resolutions below 60×80. Make sure you look at the detector resolution; some manufacturers make this confusing by adding the screen resolution in a way that can be a little misleading. Other camera manufacturers will use an image interpolation method that adds pixels through software. While this will improve the images, it will not help with temperature measurement, so ignore the interpolated resolution and only pay attention to the detector resolution.
You do not want to buy a camera and then find out that it is difficult to use. Try the camera, if possible hire one from a distributor, and then bring it into an environment like the one you intend using it in. You should be able to use the basic functions very quickly, and the menu itself should be intuitive. Or electrical inspections, there are times when your distance is restricted due to safety considerations and a telephoto lens can be used, there are also times when you are very close to the target object and a wide-angle lens helps. Building inspections can also benefit greatly with the addition of wide-angle lenses. Ideally the camera should automatically recognise the lens and select the correct calibration file, as this prevents errors on the part of the operator.
You may need a camera that has an option to add additional lenses. Not all cameras have this option. Lenses are very useful when you need a wider or narrower field of view. Overhead cables usually requires a telephoto lens, and buildings often require a wide-angle. Buying a camera with interchangeable lenses allows multiple uses.
Most cameras today are fairly robust. It is however not a good idea to drop your camera, or to use it for extensive duration in difficult environmental conditions. Look at your normal working environment and buy a camera that can be used in that. Do not get sucked into drop tests and IP ratings for cameras, simply try not to drop the camera, and don’t expose it to heavy rain conditions.
Most cameras today have an accuracy of +or- 2˚or 2%, with some of the cheaper models being +or-5˚, and some high-end ones having +or-1˚. The amount of accuracy you need will depend on the applications that you will be working with, but remember user input error may be more significant than the camera error.
This relates to the amount of images displayed on the camera per second. A higher operating frequency means better camera performance. You must remember that for most people they are looking at stationary objects, so a high frequency is not often necessary. It will however mean that you can scan around with your camera a bit faster or look at objects that are moving. If you intend working with production or R&D it may require a very high frequency camera. 9Hz may be enough for entry cameras and for basic thermography checks, over 30Hz is better for consultants and those looking for more professional thermography, and up to a couple of hundred of Hz may be necessary for specialised applications.
Most cameras today come with free software, although sometimes it functionality has been limited. Ideally the camera and software should both be able to grow with you as your needs develop. The manufacturers may have additional software available as an upgrade; this may allow the camera system to be more flexible and adaptable to your changing needs. Download evaluation copies of software and try them out. It is likely that the free software is available for you to download and practice before you buy the camera, but don’t forget to try any additional software before you make your final decision. Some cameras can also be remote-controlled via wi-fi, and may offer report writing via a smart phone or other devices, you should check this out if it is a something that you may feel necessary.
Some camera manufacturers and sales distributors offer basic training with the camera. This is not intended to make you an expert in a day or two. A level 1 course is the industry standard for entry-level thermography. It is helpful to be familiar with your camera before you attend, but not a requirement. A level 1 thermography course is intended to complement your existing training and experiences, and not intended to be the only qualification that you have. Make sure the Level 1 course that you attend has some sort of accreditation before booking a place. Also check out our blog on “Certification issues”.
Do You require a video output in your camera? This is a nice feature, although not always necessary. It is good for catching a dynamic event, and is also very useful when doing presentations, or attending trade shows. Some cameras today even include the ability to save movie files directly onto an SD card.
For most condition monitoring applications LWIR will be sufficient. MWIR may be required for high speeds, very small objects or some specialist applications.