One great advantage of OGI cameras compared with other inspection technologies is the speed in which the technology can locate leaking components without interrupting the industrial process. Historically, OGI cameras have been designed with cooled IR detectors that offer several advantages over uncooled detectors — but they often come at a higher cost. Advancements in the technology of uncooled detectors have allowed the OGI camera manufacturers such as FLIR to design and develop lower cost OGI solutions for these industries. Although lower in cost, there are some limitations to cameras with uncooled detectors versus those with cooled detectors.
THE SCIENCE BEHIND OPTICAL GAS IMAGING
Before we address the question of a cooled or uncooled detector in an OGI camera,we can explain the theory behind this technology. Optical gas imaging can be likened to looking through a normal video camera, but the operator sees a plume of gas resembling smoke blowing out. Without an OGI camera, this would be completely invisible to the naked eye. In order for you to see this plume of gas, an OGI camera uses a unique spectral (wavelength-dependent) filtering method that enables it to detect a specific gas compound.
COOLED VS. UNCOOLED DETECTORS
A cooled OGI camera has an imaging sensor that is integrated with a cryocooler that lowers the sensor temperature to cryogenic temperatures. This reduction in sensor temperature is necessary to reduce the noise to a level below that of the signal from the scene being imaged. Cryocoolers have moving parts made to extremely close mechanical tolerances that wear out over time, as well as helium gas that slowly works its way past gas seals. Eventually a rebuild for the cryocooler is required after 10,000- 13,000 hours of operation.
With uncooled filtering, you lose thermal sensitivity due to limiting the radiation that reaches the camera’s detector. This would result in a higher NETD but could present a better image related to gas imaging. As the spectral filter width is narrowed to focus on specific gases, the radiation from the scene decreases while the noise of the detector remains the same and the reflected radiation from the filter increases. This results in creating a much higher quality image related to gas imaging, but decreases the camera’s thermal sensitivity for temperature measurement (radiometry). When you have a cold filter, as in a cooled OGI camera, this phenomenon is avoided since there are very small amounts of radiation from reflections.
HOW TO CHOOSE A COOLED OR UNCOOLED OGI CAMERA
When choosing what camera you need for your OGI needs, the first factor to consider is ensuring the camera in question can visualize your gas. Increased sensitivity and image quality are important factors to consider when choosing an OGI camera. These not only impact the ability to visualize small leaks but may also be considerable factors when trying to meet regulatory standards.
There are also feature considerations when choosing a camera where a cooled OGI camera is beneficial. If you require or desire the ability to quantify your gas leak, this is solely done with an OGI camera in the midwave spectrum, such as the GF320. With the introduction of uncooled OGI cameras in the market, there are advantages of this new technology. Whether you are looking to save money, meet regulatory standards, increase worker safety, or simply to be a good environmental steward, the options are greater than ever and can sometimes be confusing. Many factors can go into a decision to choose an OGI camera beyond price. FLIR provides the widest selection and array of OGI cameras in the market and can assist in your selection process.
Learn more:
https://www.youtube.com/channel/UC2W2sBeKBrLl4Pjm0I8CA9A – Infrared learning
https://www.youtube.com/watch?v=p9i7T2aqaNM – FLIR GF series Tutorial
https://www.youtube.com/watch?v=Zdj4hdS88IA- FLIR GFX320