S-DIAS CPU UNIT
CP 733
06.12.2019
Page 21
7
Wiring Guidelines
7.1
Ground
The CP 733 must be connected to ground via the assembly on the control cabinet or over
the connection provided. It is important to create a low-ohm ground connection, only then
can error-free operation be guaranteed. The ground connection must be made with the
maximum cross section and largest (electrical) surface possible.
Any noise signals that reach the CP 733 over external cables must be dissipated via the
ground connection. High frequency noise can also be dissipated over a large (electrical)
surface (skin effect).
7.2
Shielding
The CAN, ETH1, ETH2, VAR1 and VAR2 wiring must be shielded. In addition, twisted-pair
wires must be used for the CAN bus. For wiring of ETH1 and ETH2 cables according
CAT5e
are recommended. For VAR1 and VAR2, the prefabricated VARAN cables available
from SIGMATEK in various lengths are recommended.
The low-ohm shielding must be either connected either at the entry to the control cabinet or
directly before CPU unit over a large surface (cable grommets, grounding clamps)!
Noise signals can therefore be prevented from reaching the electronics and affecting the
function.
7.3
ESD Protection
Typically, USB keyboards and mice are not wired with shielded cables. These devices are
disrupted by ESD and in some instances, no longer function.
Before any device is connected to or disconnected from the CPU unit, the potential should
be equalized (by touching the control cabinet or ground terminal). Electrostatic loads
(through clothing and shoes) can thereby be dissipated.