Emerson ROC364 Manual de Instruções descarregar pdf (Página 8)

ROC364 Instruction Manual

6-4 Rev 5/00

6.4 CONNECTING THE I/O CHANNELS TO WIRING

Each I/O channel on the I/O Card is electrically connected to field wiring by a separate plug-in terminal

block. In addition, the ROC enclosures provide a ground bus bar for terminating the sheath on shielded

wiring. The following paragraphs provide information on wiring field devices to each type of I/O

channel.

CAUTION

The sheath surrounding shielded wiring should never be connected to a signal

ground terminal or to the common terminal of an I/O channel. Doing so makes the

I/O channel susceptible to static discharge, which can permanently damage the

channel. Connect the shielded wiring sheath to a suitable earth ground only.

6.4.1 Analog Input Channels

Analog inputs (AIs) monitor current loop and voltage input devices. Each of the I/O Card analog inputs

supply source voltage for powering a transmitter, typically in a current loop installation. The signal

input range is from 1 to 5 volts. Current inputs of 4 to 20 milliamps can be used with the addition of a

250-ohm resistor across the input terminals.

The analog inputs provided on the ROC364 I/O Card are designated Point Number B1 through Point

Number B8. The terminals for connecting wiring are as follows:

T Current-limited positive battery voltage for transmitter power

+ Positive Input

- Negative Input (Common)

The analog inputs have three field terminals per channel. If an I/O Conveter Card is installed in the

ROC364 MCU, the “T” terminal provides power for loop-powered devices at 24 volts; otherwise, the

source power at the “T” terminal is the same as the 12 or 24 Vdc power supplied to the MCU. A 250-

ohm scaling resistor is supplied for use between the “+” and “-” analog input terminals.

The “+” terminal is the positive signal input and the “-” terminal is the signal common. These terminals

accept a voltage signal in the 1 to 5 volt range. Since the “-” terminal is internally connected to

common, the analog input channels function as single-ended inputs only. Note, however, that terminal

“-” is connected to an isolated analog signal common.

When wiring for a 4 to 20 milliamp current signal, leave the 250-ohm resistor installed between the “+”

and “-” terminals. Wire the current loop device “+” lead to the “T” terminal and the device “-” lead to

the AI “+” terminal. Figure Section: 6-2 shows the wiring for a typical current signal.

1 2 3 4 5 6 7 8 9 10 11 12 13 ... 19 20

Sem comentários

Emerson ROC364 Manual de Instruções Página 8