Rockwell-automation MAI32AD 32-Analogue Input Module Differential Inpu Manual de usuario descargar pdf (Pagina 9)

MAI32*A

D

October

200

5

–

Issue 4

9

Triguard

SC300E

MAI32*AD

32

-

Channel A/I Module Differential Input

THEORY OF OPERATION

Analogue input module

The

first

part

of

the

block

diagram

in

Figure

2

-

5 shows

the

circuit

used

to

process

one

of

the

32

analogue

inputs.

The

field

input

is

connected

across

a ranging

resistor

which

is

selected

in

accordance

with

the

type

of

field

input

to

be

processed

(current

or

voltage).

The

channel

signal

is

then

distributed

along

four

paths

(A

to

D);

paths

A,

B and

C are

the

triplicated

signal

processing

circuit

and

path

D feeds

the

metering

test

point.

In

each

path

the

signal

is

first

passed

through

RF

and

low

-

pass

filters

before

being

applied

to

one

channe

l of

a 32

channel

multiplexer.

For

paths

A,

B and

C a command

from

the

microcontroller

in

the

Common

Interface

is

isolated,

decoded

and

used

to

select

which

input

channel

will

be

switched

to

the

output

of

the

multiplexer.

The

multiplexer

output

is

then

buf

fered

and

sent

to

an

analogue

to

digital

(ADC)

converter

which

produces

a serial

data

output

coded

to

represent

the

amplitude

of

the

channel

input

signal.

Factory

set

links

connected

to

the

ADC

enable

the

basic

module

to

be

configured

for

different

+5Vdc

o

r +10Vdc

voltage

ranges.

The

ADC

output

is

passed

via

an

opto

-

isolator

to

the

Common

Interface

for

processing.

There

is

no

ADC

in

path

D,

the

buffered

signal

is

applied

directly

to

the

metering

test

point

on

the

front

panel.

Channel

selection

is

by

means

of

the

adjacent

channel

selector

switches.

Power

to

the

module

is

5.4Vdc

and

12Vdc

supplied

by

each

of

the

dual

redundant

SC300E

power

supply

units.

Each

line

is

divided

into

four

branches

to

provide

a supply

to

each

of

the

four

paths.

The

dual

inputs

for

both

supplies

(12V

and

5.4V)

in

each

branch

are

ORed

via

diodes

to

provide

the

dual

redundancy.

After

filtering

and

surge

limitation

the

output

rails

VEE*

(nominally12V)

and

VCC*

(nominally

5V)

provide

power

to

their

respective

paths.

The

A,

B and

C 5V

rai

ls

also

supply

power

to

the

corresponding

control

circuits

in

the

Common

Interface.

Each

of

the

A,

B and

C path

supplies

is

also

continuously

monitored

and

the

monitor

outputs

A/PSUOK,

B/PSUOK

and

C/PSUOK

are

sent

via

the

Common

Interface

to

the

MPPs

for

d

iagnostic

purposes.

An

On/off

Line

Request

switch

on

the

front

panel

enables

a request

to

be

sent

to

the

MPPs

that

the

module

be

taken

off

-

line

for

maintenance

purposes.

The

module

contains

a hardware

identity

circuit

that

enables

system

identification

o

f the

module.

Links

Only

user

changeable

link

is

identified

as

LK3

and

located

in

the

top

right

hand

corner

of

the

module

(see

Figure

1

-

1).

The

link

(LK3)

enables

the

module

to

be

set

for

321

or

320

mode.

Modes

of

operation

The

321

or

320

mode

sets

the

threshold

that

determines

how

much

of

the

circuit

can

be

degraded

while

still

preserving

overall

operation.

Setting

the

320

mode

means

that

the

system

will

continue

to

function

with

two

out

of

three

serviceable

circuits;

if

the

number

falls

to

one

out

of

th

ree

the

last

read

data

is

maintained.

In

321

mode

the

system

will

continue

to

function

with

one

out

of

three

serviceable

circuits;

if

that

fails

the

last

read

data

is

maintained

and

the

module

is

taken

off

-

line.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Comentarios a estos manuales

Sin comentarios