Racal Instruments 9916 User Manual

Racal Instruments 9916

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4.50

When

the

RESET

button

is

pressed

a

'QI

is

appl

ied

at

IC12b/l

Q

via

the

reset

circuitry.

This

puts

IC12b

into

the

preset

state.

IC12b/9

goes

to

'1',

which

is

applied

to

IC19q!2.

Since

IC19q!1

is

at

'1'

when

BURST

is

selected

IC19a

puts

a 'Q'

onto

lIC1/4,

blanking

the

display.

IC12b/8

goes

to

'Q',

holding

IC12a

in

the

cleared

state.

When

the

RESET

button

is

released

IC12b

is

freed

from

the

preset

condition,

and

can

respond

to

clocking

signals.

4.51

The

incoming

signal

to

be

measured

is

applied

to

IC12b/ll,

clockinglC12b/9

to

IQ'

and

IC12b/8

to

11'.

The

'Q'

is

appl

ied

to

IC19q!2,

removing

the

display

blanking.

It

is

also

applied

to

IC12q!2

via

C68.

When

the

'l'

at

IC12b/8

releases

IC12a

from

the

cleared

state

it

can

be

clocked

by

the

lQ

kHz

signal

at

IC12q!3,

but

since

IC12q!2

is

at

'0'

no

change

of

state

occurs.

A.s

C68

charges,

however,

IC12q!2

reverts

to

the

'1'

state,

and

after

a

delay

of

40

ms

IC12q!

6

is

clocked

to

'0'.

This

delay

provides

settl

ing

time

for

the

input

ampl

ifiers.

4.52

The

step

at

IC12q!

6,

differentiated

by

C69

and

R94/R96,

is

fed

to

IC17c/9

giving

a

positive

going

pulse

at

IC17b/5

and

IC13q!1.

IC4/13

is

taken

to

'Q' by

IC17b for

the

pulse

duration,

initiating

a

new

measurement

cycle

on

the

11'

to

IQ'

transition

and

then

returning

to

the

Hold

condition

so

that

the

display

will

be

held

at

the

end

of

the

gate

period.

IC13q!3

goes

to

'0'

and

causes

IC2b to

generate

a

stores

update

pulse

at

IC4/4.

The

circuit

will

remain

in

this

condition

until

the

RESET

button

is

pressed

again.

CHECK

MODE

4.53

With

the

FUNCT

10

N

switch

set

to CHEC K

lC8b/9

is

at

'0',

IC9c/9

and

10

are

at

'1'

and

IC24d/13

is

at

'1'.

If

'A'

Channel

is

also

selected

IC10q!1

is

at

'0',

putting

IC24cV12 to

'1'.

\C24q!

11

therefore

goes

to

'0',

and

this

level,

appl

ied

to

l1C1/3

gives

an

'all

eights'

display

for

segment

checking.

4.54

With

CHECK,and

'B'

Channel

selected

IC8b

is

inhibited

by

the

'0'

at

pin

9,

IC9a

is

inhibited

by

the

'0'

at

pins

1

and

2,

IC9b

is

inhibited

by

the

'0'

at

pin

5.

IC9c

is

enabled

by a

'1'

on

pins

9

and

10,

and

passes

the

1

MHz

from

IC4/6

to

the

-:ounter

circuits.

POWER SUPPLY

Line Power

4.55

With

the

LINE POWER/CHARGE/BATTERY POWER

switch

(52)

at

LINE

POWER

the

supply

is

fed

via

a

3-pin

plug/filter

connedtor

on

the

rear

panel,

fuse

FS50,

the

POWER swi

tch

and

552

to

the

primaries

of

T50.

The

transformer

tapp

ings

and

552

must

be

set

to

suit

the

local

supply

voltage

as

shown

in

Fig.

5.1

-

4.56

The

output

of

secondary

'A'

is

rectified

in

the

potted

bridge

rectifier

D5Q

and

smoothed

by C101

to

provide

a

supply

for

the

+5

vol t

stabil

iser.

The

output

of

secondary

'B'

is

rectified

in

the

diode

bridge

D31

to

D34

and

smoothed

by

Cl02

to

provide

the

-5

volt

stabiliser

supply.

The

-5

volt

rail

is

protected

by FS1,

which

must

be

of

the

quick

action

type.

4-8

9916Vol.2

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Racal Instruments 9916 Specifications

General

Brand	Racal Instruments
Model	9916
Category	Measuring Instruments
Language	English