Rockwell-automation MDO32BNS 32-Channel Digital Output Module Manuel d'utilisateur télécharger pdf (Page 9)

MDO32BNS October

200

5

–

Issue 7

9

Triguard

SC300E MDO32BNS 32

-

Channel Digital Output Module

The

output

switch

for

each

channel

comprises

six

FETs

connected

in

the

series/parallel

network

shown

and

providing

2 out

of

3 majority

voting

between

the

three

paths

A,

B and

C.

A front

panel

LED

at

the

switch

output

is

lit

when

the

switch

is

closed.

Voltage

and

current

monitoring

circuits

are

also

connected

to

the

switches

to

provide

outputs

for

the

Latent

Fault

Detection

(LFD)

system,

these

are

fed

back

to

the

microcontrollers

via

dedicated

shift

registers

and

opto

-

isolators.

The

feedback

information

confirms

that

the

output

has

switched

to

the

commanded

state

and

that

the

line

is

not

open

or

short

circuit

Figure

2

-

4.

FET

‘hex’

voter

Testing

of

the

output

switches

using

the

LFD

circuits

is

co

-

ordinated

by

the

microcontrollers.

When

all

outputs

are

in

the

healthy

condition

and

the

microcontrollers

confirm

no

faults

present

the

main

processors

will

instruct

each

microcontroller

in

turn

to

switch

its

output

alone

to

t

he

opposite

state

and

confirm

the

correct

operation

of

the

output

switch.

This

test

also

checks

the

integrity

of

the

output

loops

for

open

circuit

conditions.

The

module

power

requirements

are

served

from

two

different

sources.

The

power

rails

and

referen

ce

levels

for

the

system

-

side

circuits

are

derived

from

the

5.4V

and

12V

supplies

from

the

system

chassis.

The

power

rails

and

reference

levels

for

the

output

-

side

circuits

are

derived

from

the

field

supplies

and

also

serve

to

confirm

that

the

field

circuits

are

in

working

order

An

On/off

Line

Request

switch

on

the

front

panel

enables

a request

to

be

sent

to

the

system

that

the

module

be

taken

off

-

line

for

maintenance

purposes

or

returned

on

-

line.

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