Grass Valley LDK 8000 v.2.0 - Manual (Page 9)

LDK 8000 User’s Guide vii
Triax cable systems
Only connect a Triax cable from the same LDK camera family to the unit.
Do not allow system earth currents to exceed 1.5A in the outer shield of the Triax cable or
0.2A in other cable shields.
To avoid excessive earth currents in a Triax system, galvanically separate the power earth
connection of equipment connected to the camera from the camera earth.
It is strictly prohibited to short circuit the inner and outer shields of a Triax cable used to
connect a camera to a base station.
Galvanic separation
Because of the nature of Triax systems, with long distances between camera and Base
Station, the risk of earth currents flowing is greater. These earth currents can result in damage
to the equipment.
For example, a monitor connected directly to the CVBS output of the camera is powered
locally. The earthing point of the monitor’s power supply can be at a different potential with
respect to the earthing point of the Base Station. If the power earth of the monitor is also the
video earth, then this earth potential is transferred to the camera via the shield of the BNC
connector. The difference in earth potential between the camera and the Base Station results
in an earth current in the Triax system.
To prevent earth currents from flowing in the Triax system, we recommend galvanic
separation of earthed equipment connected to the camera. This separation can be achieved by
using an isolation transformer between the local power outlet and the equipment connected to
the camera. Alternatively, use equipment that has a double insulation and therefore does not
require an earth connection.