Installation
28
F-FEM-CON — User’s Guide
3.3.3
Grounding and Shielding
3.3.3.1
Grounding
For grounding, the following must be considered:
Prevent dangerous contact voltage at electrically conductive parts.
Parasitic currents must be led back to their source of origin via the shortest
route possible.
This requires low grounding resistance and compliance with the high frequency
rules regarding installation, wire types and contacting.
The F-FEM-CON is electrically isolated from the 24 V DC supply. All analog
outputs are electrically isolated from each other and from the system. The
ground wires of the individual outputs can be connected to the ground of the
measuring system (please see pin assignments in chapter Analog Outputs
X5 ... X8 on page 88). For safety purposes, the case is connected to the
ground via a PE and via the DIN rail (to avoid radio frequency interfer-
ences). The PE is carried in the power supply cable.
If several F-FEM clusters are connected with each other in a network, every
cluster should be grounded with low inductance to the ground of its local
signal source.
If an IEEE1394 interface is used, ground wires must be used between the
individual F-FEM clusters as well as between the first cluster and the host
system (PUMA test bed workstation). Potential equalization is ensured by
the PEs, which are carried in the supply lines. The ground wires minimize
the effects of the ground loop between the different ground potentials of the
network (please refer to Fig. 14 on page 30).
To avoid ground loops completely, a fiber optic link (FOL) can be used to
connect the clusters or to connect PUMA and the first cluster (please refer
to Fig. 15 on page 31). In this case, a compensatory current over the
ground wires and over the supply wire shielding is possible.
If the ground of the engine in the test cell and of the host system have to be
separated (e.g. due to too great a distance or ground loops), the F-FEM
cluster which is assigned to the engine in the test cell should have its own
24 V power supply. Then the shielding of the power supply lines of the
F-FEM cluster must be connected via a capacitor to the same PE to which
the 24 V power supply is connected. The ground wire must then be clamped
to the 0 V output of the 24 V power supply (please refer to Fig. 16 on
page 32).
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