Rockwell Automation T7470A User Manual

ICS Regent+Plus

PD-7025

Analog Output Modules

4 to 20 mA

(T7470A)

Issue 1,

Analog output modules provide 4 to 20 mA current outputs for a maximum of eight user loads per module. The module's triplicated I/O Safetybus interface ensures that no system failure will inadvertently affect the output signal, and that no failure in the module can affect the operation of the Regent system or other I/O modules in the system.

Features

March, 06

Regent

Eight 4 to 20 mA output circuits.

High resolution 12-bit D/A converter per output.

Hot-replaceable.

Automatic testing of triplicate I/O Safetybus circuits and many simplex logic circui

Front panel indicators on each module show active/fault and shutdown status.

2500 volt minimum electrical isolation between field and logic circuits.

TÜV certified, Risk Class 5, non-interfering.

Module Operation

A block diagram of the analog output module is shown in Figure 1.

The processor modules send triplicated write data commands to the output module over the I/O Safe addressing data and data write commands are voted by the module (preventing I/O Safetybus failures upstream from the

ts.

tybus. The processors’

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Analog Output Modules

module from affecting module operation). The voted result is then passed to the I/O bus interface logic.

The voted output data from the I/O bus interface logic is then used to drive individual digital-to-analog (D/A) converters per output channel. The field-side D/A output circuits are optically isolated from the I/O bus interface logic circuits and receive power fro

Each D/A output circuit provides a 4 to 20 mA output current corresponding to analog output values ranging from 0 to

4095. The analog output circuits are capable of driving external load devices up to 500 Ohms.

(T7470A)

m the external power supply.

Figure 1. Block Diagram of Analog Output Module.

Testing and Diagnostics

Each module’s voter circuits are periodically tested by the processor modules. Discrepant data are sent through one of three legs of the I/O Safet

ybus to determine whether the

module’s voter is able to outvote the incorrect data. A failure

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Analog Output Modules

Note:

to return the correct majority-voted result to the processors produces an I/O module error indication at the processor modules and a module fault indication at the I/O module.

Each type of module has a unique identification code that is read by the controller. This code lets the controller know which type of module is installed in each I/O chassis slot and how to address that module and its points specifically. module is removed, or is replaced with a module of a different type, the processor modules will indicate an I/O module error.

Loopback logic tests periodically write data to the module and then read it back to determine whether the module’s I/O bus interface logic is functioning correctly.

Whenever a module fault is detected, there will be an I/O module fault indication at the controller, the controller's fault relay contacts are actuated, and fault indication will appear on the module.

(T7470A)

If a

Front Panel Indicators

The analog output module is shown in Figure 2. The front panel contains active, fault, and shutdown indicators.

Active and Fault Status Indicators

These green and red LEDs indicate the overall health of the module. During normal operation the green ACTIVE indicator flashes at the controller's scan rate. If a module fault occurs the red FAULT indicator turns on and the green ACTIVE indicator turns off.

The module will indicate a FAULT if the field power is not applied.

PD-7025

Mar-06

Analog Output Modules

(T7470A)

Figure 2. Analog Output Module.

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Analog Output Modules

Note:

(T7470A)

Application

Shutdown Indicator

Upon loss of communications with the controller, output modules enter either a shutdown or hold fault mode. If the I/O unit is set to shutdown, the red SHUTDOWN indicator will turn on when communications with the controller are lost. If the I/O unit is set to hold, the SHUTDOWN indicator will always be off (see page 6, Fault Mode Jumper).

When the module is installed in the I/O chassi

power (from the I/O power supply modules) is first applied to the module, it will be in the shutdown mode until the first output scan, regardless of the fault mode jumper settings. Also, removing two I/O transceiver modules, two I/O power supply modules, or two power legs will cause the module to be in the shutdown mode.

s or when logic

Simplex Configuration

Analog output modules provide a suitable interface to non critical load devices. These non-critical devices typically include analog display meters, valve positioners and analog signal repeats to other electronic equipment. Although much of the circuitry of the analog output module is automatically tested, some of the logic circuits and the field-side D/A circuits are simplex and non-tested. This simplex configuration is shown in Figure 3.

Figure 3. Simplex Analog Output Configuration.

PD-7025

Mar-06

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