BRUEL & KJAER 1022 - Partial Blocking

BRUEL & KJAER 1022

60 pages

To Next Page

To Next Page

To Previous Page

To Previous Page

Loading...

from

a

logarithmic

frequency

curve

is

obtained.

A

worm

gear,

connected

to

the

capacitor

spindle,

permits

automatic

tuning

with

the

aid

of

an

external

motor,

for

example

the

motor

in

the

Level

Rec

order

Type

2305,

and

the

worm

gear

can

be

set

and

released

by

means

of

a

magneHc

clutch.

This

is

operated

from

a

switch

on

the

front

panel

of

the

oscillator

,

or

it

can

be

operated

from

an

external

switch

or

relay.

Connection

must

then

be

made

to

the

appropriate

terminals

of

the

socket

marked

REMOTE

CONTROL

on

the

front

panel,

and

the

control

switch

AUT.

SCANNING

for

the

magnetic

clutch

must

be

in

position

"

off"

.

The

end

of

the

scale

pointer

spindle

is

provided

with

a 6 nHn'

hole

.

The

arrangement

can

be

used

for

special

purpose

devices

which

are

to

be

governed

by

the

angular

position

of

the

frequency

scale

pointer.

By

means

of

a

pushbutton

marked

1ooo

c/s

REF.

SIGNAL,

an

extra

capacitor

is

introduced

in

the

tuning

circuit

of

the

variable

oscillator.

There

will

be

exactly

1ooo

c/s

at

the

output

socket

when

the

scale

pointer

is

set

to

1ooo

c/s

REF

.

SIGNAL

and

the

pushbutton

looo

c/s

REF.

SIGNAL

is

depressed

.

The

reason

for

setting

the

scale

pointer

at

looo

c/s

REF

. SIGNAL is

in

order

to

be

able

to

align

the

1022

with

the

frequency

calibrated

paper

,

used

on

the

Level

Recorder

Type

2305,

as

this

paper

is

calibrated

from

10 c/s.

The

di

·

stance

between

the

calibration

mark

of

10 c/s

and

20 c/s

on

the

recording

paper

corresponds

to

the

distance

between

looo

c/s

REF.

SIGNAL

and

20 c/ s

on

the

oscillator.

By

depressing

the

pushbutton

it

is

now

possible

to

check

that

the

level

of

the

middle

frequencies

is

within

the

divisions

of

the

paper.

The

voltage

developed

across

the

grid

of

the

variable

oscillator

is

fed

into

the

mixer

tube

and

mixed

with

the

voltage

from

the

variable-

.,u

amplifier

.

The

mixer

tube

is

of

fhe

triode

type,

whereby

a

low

hum

level

is

obtained

in

spite

of

the

AC-he

•

ating

of

the

filament.

A

low-pass

filter

having

a

cut-off

frequency

of

50

kc

/s

is

inserted

in

the

anode

circuit

of

the

mixer

tube,

thus

passing

only

the

lower

frequenc

y

obtained

by

the

frequency

conversion,

onto

the

grid

of

the

first

tube

in

the

output

amplifier

section.

Partial

Blocking

of

Frequency

Range.

As

previously

mentioned,

the

frequency

scale

is

logarithmic

and

calibrated

20-20~)00

c/

s.

When

the

capacitor

is

set

to

frequencies

above

20ooo

c/s

or

below

20

c/s

the

fixed

Oscillator

can

be

blocked,

and

consequently

no

output

voltage

will

be

obtained.

For

automatic

recording

of

frequency

characterisrtics,

i.e.

when

using

the

Level

Recorder

Type

2305,

this

is a

great

advantage

as

no

unwanted

curves

will

then

appear

on

the

corresponding

section

of

the

frequency

calibrated

paper.