Racal Instruments 9916 User Manual

Racal Instruments 9916

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Rattery

Low

Indicator

-4.65

IC6q11 is

connected

to

0

volts

at

051

collector.

The

non-inverting

input

is

connected

to

the

iunction

of

R15!VR152,

which

is

approximately

0.5

volt

lositive

with

respect

to

051

emitter.

When

the

volt

drop

across

Q51

falls

to

about

0.5

volt

IC6/1

is

at

a

potential

below

that

of

IC6/2

and

IC4"12

goes

to

'1',

lighting

LP8.

)ver

Discharge

Protection

1.66

The

Battery

Low

indicator

I

ights

when

only

a

few

minutes

of

battery

Iife

remain.

If

this

warning

is

disregarded

the

instrument

will

shut

itself

off

to

prevent

battery

damage.

L67

Rl50

and

D28

are

connected

across

Battery

A.

If

the

voltage

falls

below

about

5 vo! ts

033

will

start

to

turn

off.

Th

is

will

turn

off

036

and

render

D30

'l1effective

as

the

source

of

reference

voltage

for

IC11a.

The

voltage

of

the

+5

volt

rail

ill

fall

and

the

instrument

will

cease

to

draw

current.

)verload

Protection

4.68

Battery

B

is

protected

by

035.

In

the

event

of

overload

the

potential

across

R

154

will

turn

035

on,

and

so

shunt

the

base

current

away

from

052.

This Iimi ts

_"he

current

available

From

the

-5

volt

supply.

;TANDBY

OFf

RATION

4.69

With

153

at

OPERATE

the

base

of

050

is

connected

to

ground

via

R125,

and

it

is

able

to

conduct.

With

the

switch

at

STANDBY

050

is

cut

off

because

Q30

__

is

normally

cut

off

by

IC6b.

This

disconnects

the

~

vol t

roil

and

removes

the

reference

for

the

-5

volt

regulator.

Tbe

internal

frequency

standard

remains

powered

from a

connection

:It

050

emitter.

LP6

anode

is

also

supplied

from

this

point,

and

since

the

+5

volt

supply

~'ail

is

at

0

vol

ts

is

able

to I

ight

via

1

R3

to

indicate

the

Standby

condition.

oattery

Economy

Operation

4.70

Pressing

the

RESET

push

button

while

STANDBY

is

selected

causes

rapid

discharge

of

C83

via

D25.

This

results

in

the

potential

of

IC6b/7

falling

below

that

of

-IC6b/6,

and

IC6b/10

goes

high,

switching

on

030

and

therefore

050.

This'

restores

the

supplies,

and

the

instrument

will

operate

normally

until

C83

recharges

via

R131

and

triggers

IC6b

back

to

its

original

condition.

This

takes

about

one

rr~inute.

The

OVERFLOW/STANDBY

--indicator

I

ights

when

the

instrument

reverts

to

the

Standby

condition.

4-12

9916Vol.2

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Racal Instruments 9916 Specifications

General

Brand	Racal Instruments
Model	9916
Category	Measuring Instruments
Language	English