VIPA CP 240 RS232, Руководство пользователя

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Chapter 2 Assembly and installation guidelines Manual VIPA System 200V
2-14 HB97E - CP - Rev. 11/30
The screening of cables reduces the influence of electrical, magnetic or
electromagnetic fields; we talk of attenuation.
The earthing rail that is connected conductively to the cabinet diverts
interfering currents from screen conductors to ground. It is essential that
the connection to the protective conductor is of low-impedance as the
interfering currents could otherwise become a source of trouble in them-
selves.
The following should be noted when cables are screened:
•
Use cables with braided screens wherever possible.
•
The coverage of the screen should exceed 80%.
•
Screens should always be grounded at both ends of cables. High
frequency interference can only be suppressed by grounding cables on
both ends.
Grounding at one end may become necessary under exceptional cir-
cumstances. However, this only provides attenuation to low frequency
interference. One-sided earthing may be of advantage where:
- it is not possible to install equipotential bonding conductors.
- analog signals (in the mV or µA range) are transferred.
- foil-type shields (static shields) are used.
•
Always use metallic or metallized covers for the plugs on data lines for
serial links. Connect the screen of the data line to the cover. Do
not
connect the screen to PIN 1 of the plug!
•
In a stationary environment it is recommended that the insulation is
stripped from the screened cable interruption-free and to attach the
screen to the screening/protective ground rail.
•
Connect screening braids by means of metallic cable clamps. These
clamps need a good electrical and large surface contact with the screen.
•
Attach the screen of a cable to the grounding rail directly where the
cable enters the cabinet/cubicle. Continue the screen right up to the
System 200V module but do
not connect the screen to ground at this
point!
Please heed the following when you assemble the system!
Where potential differences exist between earthing connections it is pos-
sible that an equalizing current could be established where the screen of a
cable is connected at both ends.
Remedy: install equipotential bonding conductors
Screening of
cables