Red-lion PCU Manuel d'utilisateur télécharger pdf (Page 60)

SERIAL CONNECTIONS

Whenwiringtheterminalblockattherearoftheunit,refertothelabelwith

the terminal description for installing each wire in its proper location. It is

recommended that shielded (screened) cable be used for serial

communications. This unit meets the EMC specifications using Alpha #2404

cable or equivalent. There are higher grades of shielded cable, such as four

conductor twisted pair, that offer an even higher degree of noise immunity.

Only two transceiver wires and a common are needed.

The two data (transceiver) wires connect to the TX/RX(+) and TX/RX(-)

terminals, appropriately.

Thecableshouldconsistofashieldedtwistedpairandinsomeapplications

a signal ground may be required to establish a ground reference. The signal

ground is required if the equipment does not have internal bias resistors

connected to the RS485 transceiver lines. The signal ground is connected at

the RS485 common of only one PCU unit to the RS485 equipment. If

necessary, the shield can be used as the signal ground.

The signal input common is isolated from the RS485 common and the

analog output “-” terminal.

Note: Do not connect any of the commons to the analog output “-” terminal.

Terminal Descriptions

RS485 COMM. - Common may be required for communication hook-up.

TX/RX(+) & TX/RX(-) - The PCU transmits and receives on these two

terminals which are connected to the external device.

TX EN. - Used with a Red Lion Controls (RLC) GCM422 Serial Converter

Module (RS422 to 20 mA Loop). Otherwise not normally used.

Note: Some models do not have TX EN. This is an output used in conjunction with

interface converter Model GCM422, to convert RS485 to 20 mA current loop.

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Red-lion PCU Manuel d'utilisateur Page 60