Feature Test & Measurement


A vision for smarter testing F


or testing and measurement within electrical engineering, it is com- monplace to use infrared cameras for thermography for the early


detection of electrical faults. Infrared cameras detect heat or infrared emis- sions, with brightness in the image pro- portional to the temperature. This allows hotspots on electrical items to be quickly identified and located. While this is important, there are a


number of other applications where vision systems are used as part of the manufacturing process for electrical components, and yet still fulfill a test and measurement role. Smart cameras, where all the image


processing and measurement is done within the camera itself, have made a huge contribution to providing afford- able, simple to deploy vision inspection and measurement systems, and now a new generation of smart cameras that are capable of making 3D measurements are starting to become available.


Off to a good start Achieving a high level of quality in manufacturing means that there is less likelihood of problems arising with electrical components in use, and industrial vision systems can be used to ensure that components are made to within their manufacturing tolerance. Some practical examples illustrate how versatile vision can be. Circuit breakers can suffer considerable power loss due to excessive heat generated within the circuitry. This heat is often dissipated using square or circular molybdenum heat sinks. Vision systems can be used to inspect dimensional accuracy, sur- face quality and planarity - all factors which could affect the effectiveness of heat dissipation. Clearly measurement accuracy will


depend on the particular application, but for one manufacturer, the resolu- tion achieved for geometric measure- ments was approximately 5µm for the edge length and a range from 3,500 to 16,000µm for the diameter. The qual- ity threshold was also high for the planarity tests, where out of tolerance deformations of just a few µm could be reliably detected. Vision can also be used to check for irregularities such as blisters, deep scratches, plus bent corners or edges. In another application, industrial


vision has replaced human measure- ment of the distance between the con- tacts in electromechanical components such as relays. The use of the vision system was able to accommodate varia- tions in the shapes and specular sur-


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faces of the relay contacts in order to achieve the customer's requirements for precision and reliability. The speed and accuracy of modern vision systems means that inspection of every single component is possible and linking the vision system(s) into the production process allows automatic rejection of out of specifica- tion components. In addi- tion, using the image processing data to provide real time feedback on the process and to link into the process control system can keep a process under con- trol and minimise waste.


The smart approach Smart cameras have been available for some years. They are well suited to applications where a range of different vision measurements may need to be made at different locations within the manufacturing process, since they are completely self contained units with on-board image processing and mea- surement capability - the result of the measurement is simply output to the control system. Significant develop- ments in smart camera systems have been reduction in size (meaning that they can be located almost anywhere in the manufacturing cycle), ease of use, improved software and optical resolu- tion, and decreasing costs. The BOA smart camera from Teledyne


DALSA measures just 44 x 44 x 44mm in a IP67 rated housing. Available in both colour and monochrome versions, it fea- tures a full suite of vision tools, a web browser-based user interface and appli- cation development interface as well as inputs and outputs, illumination control and factory communications. The web browser-based user interface helps to simplify set up while the on- board software provides capabili- ties for a variety of inspection tasks, such as positioning, identification, verifi- cation, measurement and flaw detection. Measurement


tools


include distance, angle, radii and circularity. The most recent innovation


in smart camera technology is the 3D smart camera such as the


Stemmer Imaging www.stemmer-imaging.co.uk T: 01252 780 000


Above: the BOA smart camera from Teledyne DALSA


Stemmer Imaging’s Mark Williamson explains how developments within imaging products can help in test and measurement applications


Gocator 2000 series from LMI Technologies. 3D imaging is playing


an


increas ingly important role in processing and


quality control appli-


cations for defect detection, measuring volumes, or measuring elevation dimen- sions. Featuring an integrated laser line source and optics to accommodate the laser triangulation measurement tech- nique, these pre-calibrated cameras are also web browser enabled. A powerful suite of built-in measurement tools turns live 3D profiles into real time measure- ments with pass/fail decisions. A simple point and click GUI allows single or multiple measurement tools to be selected according to the application requirements. Users can even go beyond the built-in measurement tools by using ‘C’ language scripting to perform custom calculations or define unique logic deci- sions. All of the Gocators in the 2000 series are network ‘aware’ allowing one sensor to be paired with a ‘buddy’ Gocator for more sophisticated differen- tial measurement tasks. Finally, it is worth noting that


Below: web browser set up for Gocator 2000 3D smart camera


although smart camera systems are ver- satile, it is still essential that an expert assessment of the particular application is made prior to deciding what type of vision system is the most appropriate.


Enter 204 MAY 2011 Electrical Engineering


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