My company manufacturers image generation equipment (large mainframe computer) which is typically placed at a significant distance from the display device. These may be as much as 50 to 150 feet apart. In my EMC tests, I have determined that due to common mode, harmonic noise, both ends of this shielded cable must be terminated to the respective device chassis. Unfortunately, this has the potential to create significant ground loops which severely compromise the quality of the video signal. To add insult to injury, the signals within the cable are twisted pairs, differentially driven. This eliminates (as I understand it) the possibility of terminating the signal return to chassis ground at the point at which the cable exits the enclosure. So, on the surface it appears that I have the choice of meeting EMC regulations or meeting equipment performance.
My questions are as follows; 1. Is it reasonable to provide single end termination of the overall (outside) cable shield? 2. Can differentially driven signal grounds be successfully grounded to chassis return? Should they be? 3. Is it reasonable to request or demand that both devices are sourced from the same power AND/OR bonded to a common power grid? 4. Is it desirable for signal returns to terminate at the chassis ground at the point at which the cable exits the device. Thanks in advance Rick Busche Evans & Sutherland [email protected] --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators).
