GE IC754VSI06SKD, Руководство пользователя

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D e t a i l e d O p e r a t i o n
Communication Port
GFK-2357A 6" QuickPanel View Keypad
39
Connections
Connect nodes in a daisy chain fashion. Do not connect in other arrangements,
especially "star." The standards do not specify the maximum number of nodes or
devices that can be connected to a TIA/EIA 422 or 485 network. Instead, the
standards limit the number of electrical connections by specifying that a maximum
of 32 unit loads (UL) may be connected. The QuickPanel View presents one UL.
Interconnect media
Always use twisted pair cabling and group complimentary signals into conductor
pairs; TXA with TXB, for example. Use a cable with a characteristic impedance of
100 ohms to 120 ohms. A wire gauge of 24 AWG is commonly used. Maximum
cable length is 4,000' (1,219.2m), but may be less due to cable impedance,
connection quality, data rates, and other factors.
Shield is optional. See below.
Termination
Always provide proper termination at each end of the 422/485 network. The
QuickPanel View provides built-in termination resistance when pin #9 (TRMRXB)
is connected to pin #10 (RXA).
DO NOT TERMINATE EVERY NODE. ONLY TERMINATE THE END NODES.
Grounding
A signal return path between transmitting and receiving devices must be provided.
This return path is separate from the Rx and Tx data lines and the other 422/485
signals supported by the QuickPanel View and may be provided by a separate
conductor in the cable. Connect both ends of the signal return conductor to Signal
Ground (pin #7). Shielding or use of a twisted pair for this connection is not
necessary.
For installations where all devices are in the same cabinet and have the same
ground potential between devices, connecting Signal Ground between all the
devices on the 422/485 network is adequate to ensure proper voltage levels at the
devices.
However, if there is a difference in ground potential between devices, such as
when the devices are in widely separated cabinets, then signal grounds on a
422/485 network should not be tied together. The cable shield and cable ground
should be connected together at only one device, closest to the earth ground
connection.
The signal and frame grounds of the QuickPanel View are capacitively coupled,
but in some devices these ground references are connected together. Connect
Signal Ground (pin #7) to Frame Ground (pin #1) and then to earth ground on the
QuickPanel View only in the circumstance where the other devices separate their
signal and frame grounds and the QuickPanel View is the only device with frame
and signal ground connected to earth ground.