Display unit for AT Distributed Clock ready for production
A display unit that connects directly to the output of the Australia Telescope Distributed Clock (ATDC) is now at the end of the prototyping stage and is ready for production. Initially fifteen units will be produced to replace the current ATDC terminal screens at Parkes, Narrabri, Mopra and Epping.
The unit is housed in an aluminum box and uses seven segment displays as the display medium. The prototype version of the unit was used as a test bed for evaluating various techniques to reduce the amount of electromagnetic interference produced by the internal circuits from escaping to the external environment. The openings on the front panel display area posed the biggest problem. This was overcome by using a fine transparent conductive mesh over the display area to attenuate the interference.
A prototype display unit for the Australia Telescope Distributed Clock.
Pre-compliance testing using near-field probes produced very promising results. Tests were performed with and without the conductive mesh in place. A difference of 45 dB of attenuation was measured before the noise floor of the measuring instrument was reached.
To meet the requirement of an aesthetically pleasing design, a membrane which incorporates both graphics and switches, was used for the front panel. The unit will be available with a red, amber or green display area.
Paul Hales, ATNF