
Chapter 4
Technical Specifications
Page 25
Blue Chip Technology Ltd.
01270193.doc
Page 25
Electromagnetic Compatibility (EMC)
This product meets the requirements of the European EMC Directive (89/336/EEC)
and is eligible to bear the CE mark.
It has been assessed operating in our standard industrial PC. However, because the
board can be installed in a variety of computers, certain conditions have to be
applied to ensure that the compatibility is maintained. It meets the requirements of
EN55022:1995 for a Class A product subject to those conditions.
The board must be installed in a computer system which provides screening
suitable for an industrial environment.
Any recommendations made by the computer system manufacturer/supplier
must be complied with regarding earthing and the installation of boards.
The board must be installed with the backplate securely screwed to the chassis
of the computer to ensure good metal-to-metal (i.e. earth) contact.
Most EMC problems are caused by the external cabling to boards. It is
imperative that any external cabling to the board is totally screened, and that the
screen of the cable connects to the metal end bracket of the board and hence to
earth. It is recommended that round screened cables with a braided wire screen
are used in preference to those with a foil screen and drain wire. Use metal
connector shells which connect around the full circumference of the screen; they
are far superior to those which earth the screen by a simple “pig-tail”. Standard
ribbon cable will not be adequate unless it is contained wholly within the
cabinetry housing the industrial PC.
Ensure that the screen of the external cable is bonded to a good RF earth at the
remote end of the cable.
Cables which connect externally to boards at TTL levels should not exceed two
metres in length.
Failure to observe these recommendations may invalidate the EMC compliance.