Ibm 1710 User manual

Systems Reference Library

IBM

1710 Control

System

This

manual

contains

the

basic

programming

and

operating

information

required

to control industrial processes

with

the

IBM 1710 Control System. Information concerning

industrial processing

and

instrumentation is

presented

in

the

technical

language

used

in

these fields.

File No. 1710-01

Fonn

A26-5709-0

This

manual

makes

the

following

publications

obsolete:

IBM

1710

Control

System

Reference

Manual

(A26-5601-0)

IBM

Technical

Newsletter

N26-0021

IBM

Technical

Newsletter

N26-0036

(

IBM

1710

Additional

Special Features

and

Attached

Units

(A26-5660-1)

IBM

Technical

Newsletter

N26-0041

Copies

ofthis

and

other

IBM

publications

can

be

obtained

through

mM

Branch

Offices.

Comments

concerning

the

contents

of

this

publication

may

be

addressed

to:

mM,

Product

Publications

Department,

San

Jose,

California

Page

IBM

1710

Control System. .. . .. .. . .. .. .. .. . .. . . .. . ..

..

.~

Applications

...........................................

5

1710

Control System

Units..............

. . .. .. . .. . . ... 7

1710

Publications

and

Programming

Systems.

. . . . . . . . . . . . . 7

1711

Data

Converter......

....

.............

....

...

8

1712

Multiplexer

and

Terminal

Unit

(MTV)

,

Model

I

.....

10

1711

Data

Converter Features.

.......................

12

Ana1og-to-Digital

Converter

(ADC)

.......................

12

Real-Time

Clock

(RTC)

.................................

13

Terminal

Address

Selector

(TAS)

........................

14

1711

Operator's

Panel

..................................

14

1710

Special Features

and

Additional

Units.

........

15

Standard

Terminal

Block

.................................

15

Interrupt/Process

Branch

Indicator

Terminals.

. . . . . . . . . . .

..

15

Contact

Sense

Terminal

Block.

. . . . . . . . . . . . . . . . . . . . . . . . . .

..

16

Thermocouple

Terminal

Block

............................

16

Measuring

Thermocouple

Temperatures

with

the

1710

....

16

High-Speed

Contact

Sense

.................................

18

Contact

Operate

.........................................

18

Analog

Output.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

..

19

Controlling

Instrumentation

............................

20

Closed-Loop

Computer

Control.

. . . . . . . . . . . . . . . . . . . . . . .

..

21

Analog

Output

Programming

...........................

23

Analog

Output

Fail-Safe

Features

........................

24

Interrupt

................................................

25

Interrupt

Modes

of

Operation

...........................

25

External

and

Internal

Interrupts

........................

26

Random

Addressing

of

TAS

.......•.••..........•.

. . . . . . .

..

28

Process

Branch

Indicators

.................................

29

Manual

Entry

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

..

29

1710 Process

Operator

Units

...............................

29

General

Description

..........

<

•••••••••••••••••••••••••

30

IBM

1713

Manual

Entry

Unit

" . . . . . . . . . . . . . . . . . . . . . . . .

..

31

IBM

1714 Sense

Switch

Unit

.............................

32

IBM

1715

Digital

Display

Unit

...........................

33

IBM

1717

Output

Printer.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

..

34

Serial

Input/Output

Channel

...........................

36

Programming

Process

Operator

Units

....................

40

Contents

Page

1710

Instructions .

.....................................

44

Selecting

Input

Signals

and

Contacts

.....................

44

Operating

Contact

Points

and

Set-Point

Positioners

........

48

Interrupt

Routine

Instructions

..........................

48

Reading

the

Contents

of

TAS

and

RTC

into

Core

Storage

.....

49

Input/Output

Operations

with

the

1710 Process

Operator

Units

....................................

50

Branch

Instructions

....................................

50

1711

Operator's

Panel

...............................

54

System

Data

Flow.

. . .. .. .. . .. .. . ... . .. .. ... . .. .. . .. .

..

57

Appendix

A

...........................................

59

Instruction

Summary

...................................

59

Appendix

B

...........................................

62

Summary

of

1710

Features

and

Units

.....................

62

Appendix

C

...........................................

63

Significance

of

P

and

Q Addresses . . . . . . . . . . . . . . . . . . . . . .

..

63

Appendix

0

...........................................

66

IODR

Character

Code

Chart

............................

66

Appendix

E

.................................

...........

67

Abbreviations

and

Acronyms

............................

67

Table

Areas

in

Core

Storage

. . . . . . . . . . . . . . . . . . . . . . . . . . .

..

67

Bit

Configuration

of

Decimal

Digits

.....................

67

1620

Storage

Register

Functions

.........................

67

Appendix

F.................................

. .. . .. .. .

..

68

Multiply

and

Add

Tables

...............................

68

Appendix

G...........................................

69

Character

Code

Chart

..................................

69

Index

..................................................

70

Preface

Publications

for

the

1710

Control

System

have

been

adapted

to

the

new

IBM

Systems

Reference

Library

format.

This

publication

contains

the

most

current

mac

hine

reference

information

for

the

1710, a

nd

rep-

resents a

major

revision

of

information

co

ntained

in

the

public

a

tion

IBM

1710 R efej

'e

nc

e

Manual

(Form

A26-5601) .

Machine

reference

information

for

the

1710

Control

1713

Fl

·······

....

·

-.

.....

.

. .

1714

, _

~:'.

1715

System

is

contained

in

the

following

publications

:

IBM

1620 Cen

tml

Pmcessing

Unit

(

Mod

e

ll)

A26-5706

IBM

1620

Input

/

Output

A26-5707

IBM

1620 Special F

ea

tur

es

A26-5708

IBM

1710

Contml

System

(This

publication

) A26-5709

IBM

1311 Disk Storage Dri

ve

A26-5650

The

IBM

1710 Reference

Manual

(Form

A26-5601)

is

made

obso

l

ete

by

the

publi

c

ations

listed a

bov

e.

1711

~

--

~

1717

111M

1710

Conlrol

SySlcm

The

IBM

1710

Control

System

is

specially

designed

for

controlling

processes

in

such

industries

as

petroleum

refining,

chemical

processing,

electric

utility,

natural

gas transmission,

and

steel

production.

It

is

an

on-line

control

system

that

meets

the

requirements

demanded

by

industrial

processing

management

by offering versa-

tility

of

operation,

reliability,

and

ease of

expansion

through

modular

construction

of

the

System.

Reliability

is achieved

through

the

use

of

solid-state

circuitry

and

a high-speed, self-checking,

digital

com-

puter

-

the

IBM

1620.

Flexibility

is

achieved

with

the

availability

of

announced

special features

and

addi-

tional

units,

which

offer

any

degree

of

control

from

data

logging

and

analysis to

complete

closed-loop con-

trol.

The

customer

may

start

with

the

minimum

1710

System

required

to

satisfy

initial

control

and

analysis

needs,

and

selectively

add

or

substitute

features

and

units

as

control

requirements

change.

Each

control

op-

eration

can

be

financially

proven

before

a

move

toward

more

complex

control

is

made.

The

initial

investment

is

protected

because

changes

in

control

requirements

do

not

necessitate

removal

of

the

installed

1710 System.

Applications

The

IBM

1710

is

capable

of

accepting

electrical

signals,

both

analog

and

binary,

from

such

devices as

thermo-

couples,

pressure

and

temperature

transducers,

flow

meters,

analytical

instruments,

and

contacts.

It

provides

electrical

on/off

and

analog

control

signals for

the

cus-

tomer's

controlling

devices.

Typical

applications

exist

in

the

area

of

industrial

processing

and

manufacturing

quality

control.

Industrial Processing

Industrial

processing

applications

are

as

wide

and

varied

as

are

the

degrees

of

control

that

individual

processes

may

require.

All

control

is

based

on

the

col-

lection

of

process

data,

and

the

more

complex

the

control,

the

greater

the

need

for

rapid

collection

of

data.

Some

of

the

degrees

of

control

that

a 1710

Control

System

may

exercise follow

in

order

of

complexity:

Data Logging

and

Conversion. Process

data

is

sent

to

the

1710 System,

converted

into

digital

information,

and

logged

for

process

operator

and

management

re-

view.

IBM 1710 Control

System

Data Collection

and

Analysis. Process

data

is

col-

lected

by

the

computer

for

mathematical

analysis.

Cur-

rent

performance

figures

are

compared

with

those

obtained

in

the

past,

and

the

results

are

printed

for

process

operator

and

management

evaluation.

Data Evaluation

and

Operator Guidance. Process

data

is collected, analyzed,

and

evaluated

with

respect

to

previously

stored

guidance

charts.

Control

instruc-

tions

are

then

typed

out

for

the

process

and

control

room

operator,

and

messages

and

log

sheets

are

pro-

vided

for

management

review.

Process Study.

The

computer

rapidly

collects

the

process

data

that

is

necessary for

the

development

of

a

model

of

the

process.

The

model

is

developed

by

using

a

combination

of

empirical

techniques

and

observing

past

methods

of

running

the

process.

When

a

more

complete

and

more

precise

description

of

the

process

is

required,

a

model

is

constructed

by

using

such

mathe-

matical

techniques

as

correlation

analysis

and

regres-

sion

analysis.

The

process

control

program

is

then

tested

on

the

mathematical

model

prior

to

its use

on

the

process.

Extensive

operator

guide

information

is

obtained.

In

addition,

the

model

represents

consider-

able

progress

toward

closed-loop

control.

Process

Optimization.

An

extensive

computer

con-

trol

program,

based

on

the

model

of

the

process,

directs

the

1710 System. Process

data

is

continuously

collected

and

analyzed

for

computation

of

optimum

operating

instructions.

These

instructions

are

given

to

the

process

operator

via

the

computer

console

typewriter.

Closed-Loop Control. Closed-loop

control

is

the

ulti-

mate

in

industrial

process

control.

Process

conditions

obtainable

through

instrumentation

are

continuously

monitored

by

the

computer.

The

instrument

readings

are

analyzed

rapidly

and

simultaneously,

and

the

com-

putations

initiate

controlling

signals,

which

are

sent

to

the

devices

that

control

the

process.

In

addition,

input

and

output

units

located

in

the

process

area

enable

the

computer

to

send

messages

directly

to

the

process

operator.

These

messages

guide

the

operator

in

adjusting

the

status

of

instruments

lo-

cated

at

the

point

of

control.

Data

messages

based

upon

visual

observation

of

the

process

and

point-of-control

instrumentation

are

sent

back

to

the

computer

by

the

process

operator.

These

messages

are

evaluated

by

the

computer

to

provide

additional

process

control

directly

5

through

controlling

instrumentation

and

to

provide

continued

process

operator

guidance

.

Communication

between

the

co

ntrol

room

operator

and

the

pro

ce

ss

is

ma

int

a

ined

through

the

Centr

al

Processing

Unit

(cp

u).

The

console

typewriter

pro-

r 1

17

11

Data

Converter

17

12

Multiplexer

cnd

Terminal

Unit

vides l

og

sheets a

nd

messag

es

th

at

aid

man

ageme

nt

in

evaluating

pro

cess

performance.

The

speed

a

nd

reli-

ability

of

the

1710 System e

nabl

e

the

operat

ion

of

in

-

du

strial

pro

cesses at a hig

he

r level

of

performance

than

heretofore

realized.

1713 Manual

Ent

ry Unit

1714 Sense

Switch

Unit

1715

Digital

Di

sp

lay Unit

1717 Output Printer

1

620

Centr

al

Pr

ocess

ing

Un

it

Figure

I.

Data

Flow

- 1710

Control

System

6

The

IBM

1710

Control

System is co

mprised

of

the

IBM

1620

Central

Process

ing

Unit,

the

IBM

1711

Data

Con-

verter, a

nd

the

IBM

1712

Multiplexer

and

Terminal

U

nit

,

Modell.

In

a

dditi

on, all 1620

and

1710 special

features a

nd

additional

unit

s

are

ava

ilabl

e.

Appendix

B

is

a cha

rt

of

th

e

fe

a

tur

es

and

units

that

can

be

utiliz

ed

in

the

171O

Control

System. A system

configuration

showing

all special fe

at

ure

s a

nc!

ad

dition

al

unit

s a

nd

their

prerequisites

is co

nt

a

ined

in

the

publi

ca

tion

IBM

1710 System

Configumtion

(Fo

rm

G26-5693) " All

sys

-

tem

compo

n

ents

a

nd

special

features

are m

od

ularl

y

co

nstru

cted a

nd

use solid-state (

transistorized

) cir-

cuitr

y. SMS

(Standard

Modular

System) ca

rd

s (F

igur

e

2)

are

used

throughout

the

171O

System.

The

se

print

ed

circ

uit

cards

are

pluggable

.

Each

car

d co

nt

a

in

s a

ll

the

Figure

2.

IIlM

SMS

Card

1710

Control System Units

electronic

co

mponents

and

print

ed

wifing

for a

par

-

ticular

funct

i

on

or

fun

ctions.

The

use

of

SMS ca

ni

s

not

only

make

s

the

sys

tem

more

flexible

and

reliable

,

but,

in

a

ddition

, increases

it

s

reliability

a

nd

availability

be-

cause

of

redu

ced ma

int

enance

requirem

ents.

Abbrev

i

ations

and

acronoyms

used

in

this

publi

ca-

tion

that

a

re

pe

culiar to

the

1710

Contro

l System are

listed a

nd

defin

ed

in

Appendix

E.

J7J0 Publications

and

Programming

Systems

Systems Reference

Library

The

co

ntinuin

g

dem

a

nd

s

of

business a

nd

indu

s

tr

y have

ne

cessitated

the

design a

nd

manufa

c

ture

of an increas-

ing

number

a

nd

variety

of ve

rsatile

co

mputer

systems.

The

programmers

and

operators of

the

se

sys

tems

(I

re

challenged,

as

never

before

, to

learn

a

nd

implem

e

nt

effective

man-t

o-co

mputer

communications.

The

re

c-

ognition

of

this cha

lleng

e

and

the

desire

to effect the

high

est co

mmuni

cation level

between

all conce

rn

ed -

ma

nufa

c

turer,

system

eng

ineer, user, a

nd

co

mputer

-

has

re

s

ulted

in

the

es

tablishment

of

the

IBM

Systems

R

eference

Librar

y.

A Systems

Reference

Library

is

provided

for

each

computer

system. Each

referen

ce

libr

ary

includes

lit

era-

tur

e

app

li

ca

ble

to

the

install

a

tion

a

nd

operation

of

its

Figure

3.

IBM

17

11

Data

Converter

7

respective system.

The

Systems

Reference

Library

is

organized

in

three

main

categories:

1.

Systems

Information

-

Condensed:

introductory

and

summary

publications

for

machine

units

and

programming

systems

and

a

bibliography

of

all

library

literature

is

included

in

this category.

2.

Machine

Systems:

includes

a

detailed

publication

for

each

unit

and

feature

of

the

system

and

its

physical

installation

(cpu,

I/0,

Special Features,

Physical

Planning,

etc.) .

3.

Programming

Systems:

includes

general

and

de-

tailed

publications

for

each

programming

system

(SPS,

Utility

Programs,

Processors, etc.) .

1710

Bibliography (Form

A26-5695)

Reference

literature

applicable

to

the

installation

and

operation

of

the

IBM

1710

Control

System is

indexed

in

this

bibliography.

The

bibliography

is

published

in

three

parts:

In

Part

1,

the

publications

are

listed

under

major

subject

headings; this

listing

can

serve as a

table

of

contents

for

the

1710 Systems

Reference

Library.

Part

2 is a cross-index

of

publications

by

machine

type

number

to

help

the

user

find

publications

for

which

the

title

is

not

known.

Part

3

contains

the

abstracts of

all

publications

in

form

number

sequence.

The

abstract

of

a

publication

enables

the

user

to

determine

whether

the

publication

is

applicable

to

his needs.

All 1710

publications

listed

in

this

bibliography

can

be

obtained

by

form

number

from

the

local

IBM

Sales

Representative.

1710

Systems

Summary

This

publication

briefly describes system concepts,

sys-

tem

units,

and

special features.

Of

particular

impor-

tance

to

the

programmer

is

the

section

of

this

manual

that

describes

the

programs

and

programming

systems

for

the

1710

Control

System.

17JJ

Data

Converter

Figure

1

illustrated

the

relationship

between

an

indus-

trial

process

and

the

1710

Control

System.

The

1711

may

be

programmed

to

control

processes as follows

(the

numbers

correspond

to

the

circled

numbers

in

Figure

4) :

8

1.

Analog

Input

signals

are

sent

to

the

1710 System

via

the

1712

MTU.

The

1712

is

used

as

the

inter-

connecting

device

between

the

process

and

the

1710.

2.

The

Interrupt

feature

enables

the

control

system

to

give

prompt

attention

to

critical signals

caused

by

such

occurrences as

the

liquid

level

of

a

tank

approaching

an

overflow

condition.

The

interrupt

causes

the

computer

to

suspend

routine

operation,

to

notify

the

process

operator

of

the

condition,

and/or

to

initiate

corrective action.

With

the

in-

stallation

of

special features, corrective

action

can

turn

on

a

motor

in

the

process

area

which

will

close a valve

and

stop

liquid

flow

to

the

tank.

Interrupts

are

assigned

to

high-priority

condi-

tions

in

the

process

that

are

not

expected

to

occur

in

normal

processing,

or

if

they

are

expected

to

occur,

their

occurrence

cannot

be

scheduled.

With-

out

the

ability

to

interrupt

its

program

at any

time

7

the

computer

would

repeatedly

scan these

signals,

even

though

the

signals

occur

infrequently

or

not

at

all.

An

internal

interrupt,

Multiplex

Complete,

is

available

when

the

Input/Output

Interrupt

fea-

ture

is installed.

The

Multiplex

Complete

inter-

rupt

is

turned

on

by

completion

of

process

input/

output

functions

such

as

the

end

of

conversion

of

an

analog

input

signal.

The

Multiplex

Complete

interrupt

is

used

to

direct

the

computer

program

to

a

program

subroutine

that

will cause

appropri-

ate

program

action

such

as

reading

the

contents

of

the

ADC

register

into

core storage.

3.

Analog

Output

sends

computer-controlled

signal

pulses

to

the

customer's

controlling

devices

in

the

process area.

Contact

Operate

is

used

to

turn

on

or

off

the

customer's

process devices (motors,

alarms, etc.) .

4.

Up

to

20 Process

Branch

Indicators

are

available

for

program

interrogation

of

conditions

in

the

process area.

Each

Process

Branch

Indicator

re-

flects

the

on/off

condition

of

a

contact

in

the

process

area

-

if

the

contact

is closed, its associated

indicator

is

on.

When

the

contact

opens,

the

indi-

cator

is

turned

off.

Thus,

as

the

contacts

in

the

process

open

and

close,

their

respective

indicators

in

core

storage

are

turned

off

and

on.

Process

Branch

Indicators

can

be

assigned

to

signals

in

the

process

that

are

not

as

critical

as

those

requiring

the

Interrupt

feature, yet

must

be

frequently

interrogated

by

the

computer

program.

These

indicators

can

be

individually

scheduled

for

interrogation

by

the

program

at

timed

inter-

vals.

5. Process

Operator

Units

can

be

connected

to

the

1710

Control

System so

that

input

information

can

be

originated

by

the

process

operator,

or

out-

put

data

can

be

made

available

at

vital

points

throughout

the

process area.

These

units

can

be

connected

to

or

disconnected

from

the

system

without

disturbing

other

Process

Operator

Units

on

the

system,

and

without

affecting

the

operation

of

the

1620

CPU.

(

c

~

1620

Centr

ol

Processing

Unit

~

4---

- - - g

• I

,-

~

--

-\

Figure

.

. 4

Data

Flow

Diagram

of

1710

Control

System

Process

Oper

ator

1712

Multiplexer

and

Terminal

Unit

1711

Doto Converter

Control

Room

Operator

o

17

14

Sense

Swi

t

ch

Unit

1717

Output

Printer

9

6.

The

High

-S

peed

Contact

Sense

feature

e

nable

s the

1710 System

to

sense

the

on

/o

ff

condition

of

up

to

400 co

nt

acts

in

the

process.

Th

e co

nt

acts

are

sca

nned

a

nd

the

st

at

us

of

the

co

nt

acts is

placed

in

1620

core

s

tor

age

at

rates

of

up

to

10

0,000

points

per

second.

Thi

s

feature

is used to t

er

minate

th

e ma

jorit

y

of

on

/off s

ign

als

in

the

process

th

at

a

re

neith

er

cr

itical

nor

mu

st

be

interr

oga

ted

individuall

y.

These

signals may

occur

frequently

or

infr

e-

quentl

y,

but

the

y a

re

sca

nned

by

th

e co

mputer

as

a

routine

op

era

tion.

Unlike

Proce

ss

Branch

Indi

ca

tor

s

that

can

be

co

ntinu

a

ll

y

turn

ed on

and

off

inside

the co

mput

er

Figur

e 5. 1712

Multiplex

er

and

Termina

l

Unit,

Modell

10

by

the

ope

nin

g a

nd

closing

of

their

respect

ive con-

tact

poi

nt

s in

the

process, the st

at

us

of

contact

sense

points

are

recorded

in

the

computer's

core

st

orage

as

being

either

off

or

on

at

the

particular

po

int

in

time

at

which

they

ar

e sca

nned

.

A

particular

adva

nt

age

of

the

High-Speed

Co

n-

t

act

Sense

fe

at

ur

e is

th

at it can be used

with

any

in

-

dustri

al co

nt

acts

and

any

industrial

wiring.

J

7J

2

Multiplexer

and

Terminal Unit (MTUJ,

Model

J

The

1712-1

MTU

(Figure

5)

provides

interconne

ct

in

g

terminals

for

process

and

co

ntrol

system

connections

.

It

contains

space for six

terminal

blocks (50

points

per

block)

and

associated SMS cards. A

terminal

strip

may

be

installed

for

12

Process

Interrupts

and

20 Process

Branch

Indicators.

In

addition,

a

terminal

block

may

be

installed

for

terminating

as

many

as 400

contact

sense

points.

In

keeping

with

1710 System

philosophy,

all

terminal

blocks

and

terminations

are

available

as

special features.

In

addition,

the

1712-1 is

available

with

one, two,

or

three

SMS

card

panels, i.e.,

it

is

ca-

pable

of

terminating

a

total

of

150

or

300 process in-

put/

outputs

and

400

contact

sense

points.

The

design

and

construction

of

the

1712-1 offers

the

following

advantages:

(1)

multiplexing

and

terminat-

ing

in

the

same

unit

minimize

coupling

problems

be-

tween

the

process

and

the

control

system,

and

(2) system

expansion

in

the

1712

simply

involves

the

connection

of

terminal

wires

and

the

addition

of

SMS cards.

Process

Input/Output

Special Features

Analog

Input.

Low-level

voltage

and

current

signals

from

process

thermocouples

and

instruments

are

sent

to

the

ADC

in

the

1711.

High-SPeed Contact Sense. Process

conditions

are

sensed

by

the

on/off

status

of

contacts

in

the

process

area.

Process Branch Indicators. 1710

indicators

are

turned

on

and

off

by

associated contacts

in

the

process

area.

The

1710

program

interrogates

the

indicators

to

deter-

mine

the

appropriate

program

instructions

to

follow.

Interrupt.

Process

disturbances

that

require

correc-

tive

action

interrupt

the

routine

operation

of

the

1710.

Analog

Output.

Controlling

signals

are

sent

from

the

1710

to

the

customer's

set-point

positioners.

Contact Operate.

Contacts

are

momentarily

closed

to

switch process

control

devices

on

and

off.

11

1711

Data

Converter Features

The

1711

Data

Converter

contains

an

Analog-to-Digi-

tal

Converter

(ADC)

, a

Real-Time

Clock

(RTC)

, a

Ter-

minal

Address Selector

(TAS)

,

and

an

Operator's

Panel.

Analog-to-Digital

Converter (ADC)

The

ADC

enables

the

1710

to

accept

analog

voltages

or

currents

from

customer

instruments

and

transducers.

Fifty

milliseconds

are

required

for

each

analog

signal

conversion

(a

maximum

of

20 conversions

per

second) .

Analog

Input

functions,

available

in

increments

of

two,

include

SMS cards for

matching

(transforming

incoming

current

signals to

an

acceptable

voltage level)

and

filtering

(reducing

the

effect

of

spurious

signals) .

Analog

Input

functions

cannot

be

terminated

on

ter-

minal

blocks

containing

Contact

Operate

and

Analog

Output

functions.

Analog

Inputs

SMS

matching

and

filter cards Multiplexing

relay

cards

Standard

SMS cards

are

available

for

terminating

the

following

signals

which

may

be

of

either

polarity:

o

to

50 millivolts

o

to

5

milliamperes

o

to

20

milliamperes

o

to

50

milliamperes

Signal

polarity

is

determined

as a

part

of

the

function

of

signal

conversion.

SMS cards for signals

outside

of

the

ranges

listed

are

available

by special

order.

Analog

Input

The

program

selects

each

analog

signal

individually

via

TAS

(Terminal

Address Selector)

and

the

multi-

plexing

relays.

As

shown

in

Figure

6,

an

analog

signal

passes

through

a

multiplexing

relay

contact

and

into

the

ADC

(Analog-to-Digital

Converter)

.

The

converted

signal,

which

will

be

in

the

digital

range

of

0000

to

Analog-

to-

Digital

r----~

_-+_~

____

-+I

Converter

1620

Core

Storage

J.<'igure

6.

Analog

Input

Data

Flow

12

\

9999,

remains

in

the

ADC

register

until

the

program

causes

it

to

be

transferred

to

core storage.

An

ADC

con-

version

scale is

shown

in

Figure

7.

Pertinent

pro-

gramming

details follow.

If

a negative

analog

voltage

is

read

into

the

ADC,

a flag is

placed

over

the

units

digit

of

the

ADC

register

and

the

Negative

light

on

the

1711

Operator's

Panel

is

turned

on.

This

flag

bit

is

transferred

to

core storage

with

the

units

digit

when

the

transfer

from

the

ADC

register

to

core storage occurs.

If

the

analog

signal exceeds

the

range

of

its

match-

ing

card,

four

flag

bits

rather

than

the

contents

of

the

ADC

register

are

placed

in

core storage.

The

ADC

register

and

associated

1711

Operator

Panel

lights

will

contain

an

8-2

or

8-2-1

bit

configuration

in

the

high-order

posi-

tion

and

000-999

in

the

other

three

positions

depending

on

the

value

of

the

overload

signal.

When

the

four

digits

from

the

ADC register

are

trans-

ferred

to core storage,

the

high-order

digit

is

flagged.

The

replaced

data

including

flag

bits

is

lost.

Once

the

converted

data

is

in

core storage,

the

pro-

gram

transforms

the

digital

value

into

a

meaningful

measurement

of

the

variable

(temperature,

flow

rate,

pressure, etc.) .

Two

Program

Select

instructions:

Select Address

and

Select

ADC

Register

are

available

for

reading

analog

ADC INPUT

DIGITAL

0-50 1-5 4-20 10-50 OUTPUT

Millivolt

Milliamp

Milliamp Milliamp

+50

and

5

and

20

and

50

and

over

over over over

0000

+49.995 4.995 19.995 49.995

9999

+40

4

16

40

8000

+30

3

12

30

6000

+20

2 8

20

4000

+10

1 4

10

2000

0 ---

0000

-10 -1

-4

-10

2000

-20

-2

-8

-20

4000

-30 -3 -12 -30

6000

-40

-4

-16 -40 8000

-49.995 -4.995 19.995 -49.995

9999

-50

and

-5

and

20

and

50

and

0000

under

under under

under

Figure

7.

ADC

Conversion

Scale

signals

into

the

ADC

for conversion. Select

Address

and

Select

ADC

Register

are

provided

with

Random

Ad-

dressing of

TAS,

a special

feature.

The

Select

Address

instruction

merely

reads

the

selected signal

into

the

ADC for conversion, whereas

the

Select

ADC

Register

transfers

the

contents

of

the

ADC register

into

core stor-

age first,

and

then

reads

the

newly selected

analog

sig-

nal

for conversion.

The

Multiplexer

Busy

indicator

(29)

is

on

during

the

50

millisecond

conversion

cycle.

This

indicator

may

be

interrogated

to

determine

when

conversion

is com-

pleted.

The

computer

proceeds

with

succeeding in-

structions

during

conversion

unless

an

instruction

that

uses

the

multiplexer

is

initiated

(Analog

Input,

Analog

Output,

or

Contact

Operate

instructions)

.

In

this case,

both

the

instruction

and

the

computer

are

delayed

until

after

conversion

is

completed

and

Multiplexer

Busy

is

turned

off.

The

Multiplex

Complete

indicator

(40) is

turned

on

at

the

end

of

conversion.

Multiplex

Complete

initi-

ates

an

interrupt

which

can

cause

reading

of

the

ADC

register, selection

of

the

Input

address, etc.

It

is

often

desirable

to

take

successive

readings

of

an

input

variable

in

order

to assure

that

no

error

occurred

in

the

measuring

of

the

variable

or

in

the

analog-to-

digital

conversion

of

the

measurement.

By

taking

three

separate

readings,

the

output

of

all

three

readings

may

be

compared

against

a

predetermined

range.

If

all

three

readings

lie

within

a specified

range,

the

first

reading,

or

perhaps

an

average

of

the

three

readings,

may

be

used

with

more

certainty

as

the

value

of

the

input

vari-

able. '!\Then this

is

done, a

time

delay

of

600 ms

should

be

programmed

between

successive

readings

of

the

same

point

to

ensure

maximum

accuracy.

Real-Time

Clock

lRTCJ

The

RTC

designed

for use

in

logging

applications

is

an

electronically

powered

24-hour

mechanical

device

which

keeps

time

(to

the

nearest

minute)

in

hours,

tenths

of

hours,

and

hundredths

of

hours.

The

contents

of

the

RTC,

00.00

through

23.99,

are

displayed

on

the

1711

Operator's

Panel,

and

may

be

read

into

core stor-

age by use

of

the

Select

Real-Time

Clock

instruction.

The

low-order

position

clock

wheel

advances

once

each

minute,

as follows: 0-2-3-5-7-8-0.

The

RTC

may

be

programmed

so

that

the

logging

time

is

printed

along

with

log

data.

To

prevent

the

possibility

of

erroneous

readings,

readout

of

the

RTC

is

blocked

during

the

time

the

clock wheels

advance

(approximately

320 milliseconds) .

Three

levers

are

provided

on

the

1711

Operator's

Panel

to

set

the

clock.

The

levers

travel

up

and

down

13

as

their

respe

ctive clock wheels

advance.

The

hun

-

dredths

of

h

ours

(

rightmo

st) lev

er

mu

st

be

pos

itioned

by

the

clock to its

upward

limi

t

of

travel

before

it

can

be used to set its clock

wheel.

Terminal Address Selector

(T

AS)

TA

S is

progr

am

-c

ontro

ll

ed to select

indi

v

idual

pro

cess

si

gna

l

s.

Consisting

of

a 3

00-point

scann

ing co

unter

and

matrix

a

nd

a

three-digit

register,

TA5

se

lects

Ana

log

Input

,

Analog

Output

, a

nd

Contact

Op

e

rate

addresses

from 000 to 299;

Hi

gh-Speed

Contact

Sense a

ddr

ess

from 00 to 19; a

nd

Pro

cess

Op

e

rator

Units

addresses

from 00 to 99.

TAS

co

ntents

are

dis

play

ed on

the

17

11

Op

e

rator

's Panel.

Th

e Select

TAS

inst

ru

c

tion

Ill

ay be

Figur

e 8. 17

11

Op

e

ralor's

Pan

el

used

to

store

the

conten

ts of

TAS

.

For

the

purposes

o[

pr

ogra

mmin

g a

nd

timi

ng

considerat

i

ons

, it

is

impor-

ta

nt

to n

ote

(see

Figure

6)

th

at

Analog

I

nput

,

Ana

l

og

Output,

and

Conta

ct

Op

erate

addr

esses

ar

e

ro

ut

ed

through

the

Multiplexer,

a

nd

that

the

Pro

cess

Operator

Units

ad

dr

esses a

nd

the

High

-

Speed

Contact

Sense ad-

dre

sses are

not

ro

ut

ed

through

the

Multip

l

exer

.

The

sign

ifi

ca nce

or

this fact is mentioned in

appropriate

part

s of the ma

nu

a

l.

1711 Operator's Panel

Th

e

1711

Oper

ato

r's Panel (Fig

ur

e 8)

conta

ins

switches, keys,

light

s,

a

nd

indi

cato

rs

that

are

pertinent

to

opera

ting

the

1711

.

The

Oper

ator's

Pa

nel

is

de-

scribed

in

d

eta

il

und

er

17

11

OPERAT

ING

KEYS

AND

I.I

GHTS.

Flexibility, a

major

advantage

that

permits

the

1710

Control

System

to

meet

individual

customer

require

-

ments,

is

achieved

through

the

installation

of

an-

nounced

special features

and

additional

units. A mini-

mum

1710

Control

System may be

installed

for

existing

needs, a

nd

the

installed

system may be

altered

as con-

trol

requirements

change

to

provide

new

functions

and

increased capabilities.

This

sec

tion

describes

the

1710

special features

and

additional

units.

The

publication

IBM

1710 System Configuration

(Form

G26-5693) shows

all special features

and

additional

units

and

their

pre-

requisite

s.

Four

types

of

terminal

blocks are

available

for in-

stallation

in

the

1712

Multiplexer

and

Terminal

Unit:

Sta

ndard

Terminal

Block,

Thermocouple

Terminal

fi

g

ur

e 9.

Te

rminal

Block

1710

Special Features

and

Additional Units

Block,

Interrupt

/Process

Branch

Indicator

Terminals,

and

Contact

Sense

Terminal

Blocks.

Standard Termi

nal

Block

The

standard

terminal

block

(Figure

9)

may be used

to

connect

Analog

Input,

Contact

Operate,

and

Analog

Output

functions.

The

following

rules

must

be ob-

served, however:

Contact

Operate

and

Analog

Output

functions may

be

connected

on

the

same block.

In

order

to

minimize

undesirable

stray voltage effects,

Analog

J

nput

func-

tions

must

be

located

on

a block

containing

only An-

alog

Input

functions

.

Analog

Output

functions

require

two addresses for

each

analog

output

channel.

In

addition,

two addresses

must

be assigned for

control

of

the

slew

and

trim

oper-

ations.

Fifty

terminal

addresses

or

100

terminals

are pro-

vided for

customer

connections

on

each

block.

Analog

Input

terminations

other

than

thermocouple

terminations

can

be

made

on

a

thermocouple

terminal

block.

Analog

Output

and

Contact

Operate

termi-

nations

can

only

be

made

on

a

standard

terminal

block.

Interrupt/

Process

Branch

Indicator Terminals

This

terminal

block

is

used

to

terminate

the

12

Ex-

ternal

(process)

Interrupts,

and

the

20 Process

Bran

ch

Indicators.

15

Contact

Sense

Terminal

Block

This

terminal

block

is

used

to

terminate

high-speed

contact

sense

terminal

points.

Each

block

provides

for

termination

of

50

contact

sense connections.

Thermocouple Terminal

Block

The

thermocouple

block

is a

standard

terminal

block

that

has

been

modified

for

thermocouple

terminations.

A

thermocouple

is a

temperature-measuring

device.

It

provides

an

analog

voltage

which

is

developed

by

the

difference

between

the

ambient

temperatures

of

the

thermocouple

measuring

junction

and

the

thermo-

couple

block

reference

junction.

A resistance

bulb

thermometer

(RBT)

and

its associated

circuit

compo-

nents

are

mounted

on

the

block

to

measure

the

refer-

ence

temperature.

The

RBT

circuit

also

provides

a refer-

ence

voltage

signal

(VR)'

The

1710 uses

the

thermo-

couple,

RBT~

and

VR signals

to

compute

the

measured

temperature.

Analog

Input

terminations

other

than

thermocouple

terminations

may

be

made

on

a

thermocouple

block.

Analog

Output

and

Contact

Operate

terminations

can

only

be

made

on

a

standard

terminal

block.

Fifty

terminal

addresses

or

100

terminals

are

pro-

vided

for

customer

connections

on

each

block.

The

RBT

and

VR

must

be

assigned

to

the

first two (lowest-

numbered)

addresses

on

the

thermocouple

block.

Measuring Thermocouple Temperatures

with

the 1710

The

1710

Control

System is

connected

to

each

process

thermocouple

via

the

1712

MTU.

The

thermocouple

16

measuring

junction

is

located

in

the

process

area

where

temperature

sensing

is desired,

and

the

reference

junc-

tion

is

located

on

the

1712

terminal

block.

The

refer-

ence

junction

wires

are

extended

to

a

matching

card

in

the

1712.

The

1710 compensates for

reference

tem-

perature

fluctuations

by

means

of

an

RBT~

located

on

each

thermocouple

terminating

block

for reference-

temperature

sensing,

and

through

calculations

per-

formed

as

part

of

the

program.

Resistance Bulb

Thermometer

(RBT)

Essentially,

an

RBT

is a

wire-wound

resistor whose elec-

trical resistance varies

with

temperature.

The

resistor

is

electrically

connected

to

a

Wheatstone

bridge

(bal-

anced

circuit)

. A

temperature

variation

causes a

change

in

resistance

and

a

consequent

unbalance

of

the

bridge

circui

t.

The

RBT

circuit

provides

two

signals

for

1710

program

evaluation:

the

voltage

produced

by

the

RBT,

and

an

RBT

reference

voltage.

Thus,

not

only

are

ther-

mocouple

signals

compensated

for

by

reference

temper-

ature

fluctuations,

but

the

reference

temperature

signal

itself is

read

by

the

computer

to

permit

compensation

for

any

RBT

supply

voltage

variations

that

may

occur.

Thermocouple

Programming

and

Conversion

The

conversion

of

a

thermocouple

signal

to

a

meaning-

ful

and

accurate

temperature

value

is

performed

as

part

of

the

computer

program.

The

signals

from

the

thermo-

couple

and

the

RBT

circuit,

plus

and

RBT

data,

provide

the

means

for

mathematical

anal-

ysis

and

conversion.

Thermocouple

data

is

available

from

commercial

sources for

each

thermocouple

type,

i.e., tables

and

curves

which

express

the

temperature-

to-millivolt

relationship.

Data

for

the

RBT

supplied

with

the

thermocouple

terminal

block

is

provided

be-

low.

Three

points

should

be

stressed

about

the

con-

version

procedure

which

follows:

(I)

It

is

recognized

that

there

are

other

means,

such

as

curve

fitting,

to

convert

thermocouple

signals, (2)

The

procedure

be-

low is

valid

only

where

the

RBT

supplied

with

the

ther-

mocouple

terminal

block

is used,

and

(3)

This

pro-

cedure

pertains

to

the

signal

conversion

of

only

one

thermocouple

type, i.e.,

constants

A, B, C,

and

D (see

below)

must

be

computed

and

stored

for

each

ther-

mocouple

type:

1.

Study

the

thermocouple

temperature-to-millivolt

curve

and

determine

the

number

of

segments

or

divisions

that

must

be

made

to

obtain

the

desired

degree

of

accuracy.

For

example,

a

-100°

to

+500°

temperature

range

may

be

divided

into

four

segments as follows:

-100°

to

+50°, 500

to

2000, 2000

to

3500,

and

350°

to

500°.

This

segmentation

is

required

because

thermo-

couple

millivolt

output

is

not

a

straight

line

rela-

tionship

with

respect

to

measured

temperature-

particularly

at

the

upper

end

of

the

thermocouple

temperature

range.

Smaller

segments,

of

course,

provide

a

more

linear

or

straight

line

approxima-

tion.

2.

Take

the

upper

and

lower

millivolt

values

from

each

segment,

and

use

the

relationship,

I

millivolt

equals

a

DRO

(digital

readout)

value

of

200,

to

obtain

equivalent

DRO

values.

The

DRO

value

for a

given

thermocouple

signal

is

the

same

as

the

digital

value

obtained

in

the

ADC

register

for

that

same

thermocouple

signal.

For

example,

a 15-

millivolt

value

is

equal

to

a

DRO

value

of

3,000

(15 X 200)

and,

where

the

ADC

range

is

+50

mil-

livolts, a 15-millivolt

thermocouple

signal

is con-

verted

to

3,000 by

the

ADC.

Since

all

thermocouple

signals

are

converted

to

digital

values,

the

use

of

DRO

values

rather

than

millivolt

values facili-

tates

the

computation

of

actual

temperatures.

3.

For

each

segment, use

the

formula

temperature

= A

(DRO)

+B

twice

to

solve for A

and

B,

the

two

unknowns,

i.e., solve

once

for

the

upper

temperature

and

DRO

values

and

once

for

the

lower

temperature

and

DRO

values. Actually, A

is

the

slope

of

the

segment

and

B

is

the

intersection

of

the

segment,

if

extended

on

the

y-axis.

4.

Store A

and

B for

each

segment.

5. Use

the

same

formula

(step 3)

to

solve

for

A

and

B

in

the

temperature

area

of

25

0 C,

which

is

the

normal

temperature

region

for

the

RBT

(approxi-

mate

room

temperature).

Use these A

and

B

values

in

the

following

formulas

B

D=-j\

These

two

formulas

express

the

thermocouple

block

RBT

relationship

to

the

thermocouple

sig-

nal;

C

and

D

are

used for

the

linear

conversion

from

temperature

to

DRO

of

the

computed

RBT

temperature

(step 8) .

6.

Store

C

and

D. You

now

have

stored:

(1) a

pair

of

constants, A

and

B, for

each

segment

of

the

curve,

and

(2)

constants

C

and

D for

the

base

temperature

of

the

RBT.

7.

Read

both

signals

of

the

RBT

circuit

and

use

their

ADC

values

in

the

formula

RBT

t = 28.82

(RBT

r ) + 5.0

to

solve for

the

RBT

temperature

(RBT

t

).

RBT

and

RBTr

are

the

ADC

values

obtained

by read-

ing

the

RBT

signal

and

the

RBT

reference

signal

(the

first two addresses

on

the

thermocouple

block).

The

values, 28.82

and

5 (expressed

in

degrees

Centigrade),

are

constants

for

the

RBT

supplied

with

the

thermocouple

block.

These

values

must

be

converted

to

degrees

Fahrenheit

if

the

thermocouple

tables

and

curves

are

ex-

pressed as

such

(F =

9/5

(C) + 32) .

8.

Use

the

formula

CRBT

= C

(RBT

t) +D

to

obtain

a

corrected

DRO

value

for

the

RBT

(CRBT).

C

and

D were

obtained

in

step

5;

RBT

t was

obtained

in

step

7.

9.

Read

the

thermocouple

signal,

and

use its

ADC

value

in

the

formula

ATC=TC

+

CRBT

to

obtain

an

adjusted

DRO

value

(ATC).

]0. Use

the

formula

TC

t

=A(ATC)

+B

to

compute

the

actual

thermocouple

temperature

(TC

t

).

A

and

B

are

selected

according

to

the

DRO

value

of

ATC,

i.e.,

whatever

segment

the

value

of

A

TC

falls into,

the

A

and

B values

are

used

from

that

segment.

Example

of

Thermocouple Conversion

Example:

An

iron-constantan

(type

J)

thermocouple

is

installed

in

a

temperature

region

of

8000 C.

The

A

and

B values for

the

segment

that

includes

800°C

are:

A = .07803, B = 89.554.

The

A

and

B values for

the

segment

that

includes

25°C

are: A = .096], B = .385.

From

step

5:

C = 10.4

and

D =

-4.0

Assume

the

RBT

temperature

(RBT

t)

IS

25°C;

then

from

step

8:

CRBT=256.0

Assume

the

ADC

or

DRO

value

of

the

thermocouple

is 9236;

then

from

step 9:

ATC

= 9492

and

from

step

10:

17

High-Speed Contact Sense

High-Speed

Contact

Sense,

available

as a special

feature,

gives

the

1710

the

ability

to

determine

the

status

of

on/off

conditions

in

the

process area.

It

is

especially

suited

for

control

system

applications

that

require

very fast sensing

of

process

contacts

and

for

reading

the

many

types

of

contacts

used

in

industrial

processing.

Contact

sense

points

are

available

in

incre-

ments

of

five,

with

a

maximum

of

400

on

anyone

system.

Description

Contact

sense

points

are

terminated

in

blocks

of

50

points

each.

One

terminal

address

is

assigned

for

a

group

of

20

terminal

points. A

total

of

20

terminal

addresses

is

available

if

all

400

contact

sense

points

are

installed.

For

the

purposes

of

programming,

the

ter-

minal

block

can

be

thought

of

as

consisting

of

two

parts

with

200

terminal

points

(lO

terminal

addresses)

on

each

part.

When

a

program

instruction

specifies

anyone

of

the

10

terminal

addresses

on

either

part,

the

20

terminal

points

at

that

address

and

all

of

the

terminal

points

tor

the

remaining

higher-numbered

terminal

addresses

tor

that

part

are

scanned

and

read

into

core

storage.

For

example,

in

the

following

chart

of

terminal

addresses

it

can

be

seen

that

an

instruction

specifying

terminal

address 03 causes

the

program

to

scan

and

read

into

core

storage

terminal

points

60

through

]99.

Terminal

Points

Terminal

Points

Addresses

Scanned

Addresses

Scanned

00 000-199

]0

200-399

01

020-199

11

220-399

02 040-199

]2

240-399

03 060-199

]3

260-399

04 080-199

14

280-399

05 ]00-199

15

300-399

06 120-199

16

320-399

07 ]40-199

17

340-399

08 ]60-199

18

360-399

09 180-199

19

380-399

As

another

example,

terminal

address

10

would

cause

the

program

to scan

and

read

into

core

storage

terminal

points

200

through

399; thus,

up

to

200

terminal

points

can

be

read

with

one

instruction.

Contact

points

are

scanned

and

read

into

core

stor-

age

at

the

rate

of

100,000

points

per

second.

When

fewer

than

200

points

are

scanned,

the

rate

is

less

than

100,000

points

per

second.

18

Table

1

contains

examples

of

actual

scanning

rates.

The

program

instruction

associated

with

the

High-

Speed

Contact

Sense

special

feature

is Select

Contact

Block.

Table

I.

Examples

of

High-Speed

Contact

Sense

Scanning

Rates

Number

of

Number

of

Time in Scanning Rate

Points Computer Microseconds

in

Points

Scanned Instructions

per

Second

20

1

335

59,000

100

1 1,035 96,000

200

1 1,910 105,000

400

2 3,820 105,000

Contact Operate

The

Contact

Operate

feature

enables

the

1710

to

con-

trol

on/off

conditions

in

the

process

area.

Motor

start-

ups,

annunciators,

horns,

alarms

-

any

device

which

can

be

controlled

by

a

momentary

contact

closure

may

be

programmed.

Contact

Operate

functions

are

available

in

incre-

ments

of

two.

They

may

be

terminated

on

the

same

terminal

block

with

Analog

Output

functions,

but

not

with

Analog

Input.

The

special

feature,

Random

Ad-

dressing

of

TAS)

is

required.

Contact

Operate

utilizes

mercury-wetted

relay switches

for

its

operation.

Application

A

simplified

Contact

Operate

circuit

is

shown

in

Figure

]0

to

point

out

the

following:

].

Customer

power

is

used

to

operate

a

customer's

device

(an

alarm

in

this

case) -

the

Contact

Oper-

ate

function

merely

completes

the

circuit.

The

contact

capacity

is

100

volt-amperes

with

a 2-am-

pere,

120-volt

AC

or

24-volt

DC

maximum.

Note

that

the

contact

lines

are

fused

within

the

17]

2.

The

customer's

relay

is

energized

when

the

Con-

tact

Operate

instruction

is

executed.

The

relay

contact

R-l

closes

and

the

alarm

is

activated.

3.

The

customer

relay

circuit

mayor

may

not

be

self-latching.

The

relay

shown

is

latched,

that

is,

held

energized

by

its R-2

points.

An

unlatching

method

such

as a

push

button

may

be

provided

by

the

customer.

4.

Adequate

arc

suppression

must

be

provided

by

the

customer

for

contact

protection.

For

addi-

tional

information,

refer

to

IBM

1710

Control

Sys-

tem

Installation

Manual

-Physical

Planning

(Form

C26-5605) .

Contact

Operate

Function

latching

Relay

I R-2

~~~~~

____________

Q)_I~~----~r-

____

-+

____

~

__

+-

__

~

17121 Process

o

Circled

numbers

refer

to

text

Figure

10.

Contact

Operate

Logic

Contact

Operate

Programming

The

Contact

Operate

instruction

Select

Address

and

Contact

Operate

initiates

a

contact

closure

of

50 ms.

The

Multiplexer

Busy

indicator

is

on

during

this

time.

If

the

multiplexer

is

busy

when

the

Select

Address

and

Contact

Operate

instruction

is

initiated,

the

instruc-

tion

is

delayed

until

the

Multiplexer

Busy

indicator

goes off.

The

computer

is

disconnected

160

fLsec

after

initiating

the

instruction.

1£

the

computer

is discon-

nected

before

an

instruction

using

the

multiplexer

is

initiated

and

before

completion

of

the

50

ms

interval,

the

instruction

is

delayed

for

the

remainder

of

the

50

~~

Controlling

IActuators

~I

Process 1

Instrumentation 1

+

I

Set-Point

I

Positioners Process Area

----

Control System

I Analog

Contact

1712

MTU

Output

Operate

I 1711

t 1 1620

Figure

11.

On-Line,

Closed-Loop

Control

ms.

1£

the

Input/Output

Interrupts

special

feature

is

installed,

a

Multiplex

Complete

Interrupt

signal

occurs

after

the

50-ms

interval.

Analog

Output

The

Analog

Output

feature

enables

process

engineers

to "close

the

loop"

with

the

IBM

1710

Control

System.

Process

instrumentation

provides

data

to

the

computer

which,

after

programmed

analysis

of

the

collected

data,

returns

controlling

signals to

the

process

via

the

Analog

Output

and

Contact

Operate

features

(Figure

11) .

All

Measuring

Instruments

--

High-Speed

Analog I

Contact

Sense Input

ADC I

19

process

instrumentation,

both

measuring

and

controll-

ing, is

provided

by

the

customer,

as

are

the

set-point

positioners,

to

alter

the

set-point

adjustments

on

con-

trolling

instrumentation.

The

controllers

regulate

the

actuators

(valve

motors

and

valves,

dampers,

relays,

solenoids, etc.)

that

implement

process

control.

The

Analog

Output

feature

has

been

designed

so

that

the

customer

has

maximum

control

over

his

out-

put

functions.

Controlling Instrumentation

A

home

furnace

thermostat

is

a

controlling

instrument.

Depending

on

feelings

of

coolness

or

warmth,

the

householder

adjusts

the

thermostat

(set-point)

up

or

down.

The

difference

between

the

room

temperature

and

the

temperature

specified by

the

set-point

causes

a

signal

that

controls

the

fuel

supplied

to

the

furnace.

The

resulting

change

in

BTU

output

from

the

furnace

corrects

the

room

temperature

to

the

temperature

spec-

ified

by

the

set-point.

Industrial

controlling

instruments

are

generally

more

complex,

but

contain

essentially

the

same

ele-

ments:

A

device

for

measuring

the

value

of

variable.

An

adjustable

set-point.

A

control

mechanism

for

maintaining

the

meas-

ured

variable

at

the

value

specified by

the

set-

point.

In

addition

to these basic elements, a

controlling

in-

strument

mayor

may

not

have

associated

with

it

an

indicator

and/or

a

recorder.

An

indicator

provides

a

continuous

visual

indication

of

the

measured

variable,

e.g.,

the

thermometer

mounted

on

the

home

thermostat.

I

Set Point

Flow Recorder Controller

}'igure

12.

Automatic

Control

Loop

20

A

recorder

provides

a

continuous

record

of

the

meas-

ured

variable.

Controlling

instruments

are

generally

named

according

to

the

scope

of

their

functions

-re-

cording,

indicating,

and

controlling.

For

example,

an

instrument

consisting

of

all

three

units

is

referred

to

as

an

Indicator/Recorder

Controller;

an

instrument

consisting

of

a

recorder

and

a

controller

is

referred

to

as a

Recorder-Controller,

etc.

A basic

automatic

control

loop

for

regulating

fluid

flow is

shown

in

Figure

12.

The

variable

is

measured

and

transmi

tted

to

the

Flow

Recorder-Con

troller

by

Flow

Transmitter

1.

The

controller~

which

mayor

may

not

be

mounted

inside

the

instrument,

acts as

an

analog

computer

in

that

it

determines

the

difference

between

the

measured

variable

and

the

set-point

value.

This

difference,

if

present,

results

in

a

corrective

signal

to

the

actuator

or

controlling

valve, V.

Thus,

the

fluid flow

is

maintained

at

the

value

specified

by

the

position

of

the

set-point.

When

the

process

requires

a

change

in

flow

rate,

the

process

operator

repositions

the

set-point

up

or

down.

Most

process

instrumentation

set-points

are

adjusted

by

the

operator.

Some

control

problems,

however,

re-

quire

that

the

set-point

of

an

instrument

be

automati-

cally

adjusted

by

the

controller

of

another

instrument.

This

form

of

control

is

designated

as

Cascade

or

Mul-

tiple-Loop

control.

Cascade

control

may

be

employed

to

regulate

the

supply

of

fuel

to

a steel-mill

furnace.

The

fuel,

coke

oven

gas,

is

obtained

as a

byproduct

of

another

operation

and

as a

result

its

pressure

in

the

fuel

line

varies

considerably.

The

demand

for

furnace

heat

also varies

and

Cascade

control

is

employed

to

compensate

for

both

variables

(Figure

13).

Fluctua-

tions

in

furnace

temperature

are

sensed by

the

thermo-

couple

(T

/ c) .

The

temperature

Indicator

/Recorder,

T,

v

IBM 1710 User manual

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