01/01/2015 Custom Veroshield rack case helps the BBC improve audio codec
BBC Research and Development is at the forefront of the global broadcast industry’s mission to improve the programmes’ quality of both video and audio. Their recent research into further improvements in the performance of the widely-used NICAM Codec has been supported by customised EMC –screened 3U 19-inch rack cases from Verotec.
The modifications to the standard unit included a four-ink CMYK digitally printed front panel, which enabled a very subtle image with more than 64000 different colours to be faithfully reproduced across the complete surface of the panel, without any margins being needed around the periphery. A very dense pattern of connector cutouts was required on the rear panel; these were laser cut to maintain the flatness of the panel, an issue if the more usual punching had been employed. A ventilation aperture was required in each side panel, these were created using an EMC-compliant hole pattern to minimise any loss of attenuation. Given the application, good EMC performance was a key criterion, and easily achieved by the Veroshield rack case, which has typical attenuation figures in excess of 110 dB up to 10 MHz, falling linearly to 40 dB at 1 GHz.
Veroshield is constructed from 0.9 mm zinc plated steel to maintain electrical conductivity throughout the unit; an additional 19” aluminium front panel, external to the screened enclosure, is provided to improve the appearance when the unit is mounted in a rack or desktop case. Removable top and bottom covers facilitate easy access to the internal components; they are secured with multiple fixings around their periphery to ensure that slot lengths are kept to a minimum to preserve the high levels of attenuation.
Verotec use ArtCAM Express middleware in conjunction with their CAD systems. It allows customers to send Pro Eng, Solid Works, AutoCAD or PDF files of their modified panels; these drawings are then automatically translated into the standard MCR file format required to control the CNC manufacturing machines, avoiding any potential inaccuracies. A further benefit is that the data path from customer to machining centre is homogeneous, ensuring that ISO9001 traceability is preserved to allow batch traceability if required.