Amber 5500 - Input Selection; Input Termination

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Programmable

Audio

Measurement

System

'

Section

2

Amber

model

5500

Owner’s

Manual

Version

07

2.1.10

INPUT

SELECTION

One

of

three

(four)

possible

inputs

may

be

selected:

INPUT

A,

INPUT

B

or

OSCillator

A

(or

OSC

B).

A

and

B

are

two

identical

inputs

on

the

front

panel.

OSC

is

the

signal

at

the

generator

output

and

is

used

for

self-check,

send

level

verification,

etc.

To

select

the

os-

cillator

output,

push

and

hold

the

SHIFT

key

and

the

A

button.

If

the

optional

B

OUTPUT

is

provided,

it

may

be

selected

by

pushing

and

holding

the

shift

button

while

pushing

the

B

button.

2.1.11

INPUT

TERMINATION

All

inputs

are

normally

high

impedance

bridging

(100

k

ohms)

but

may

also

be

set

to

a

600

or

150

ohm

termination.

(Note

that

the

input

termination

operates

on

external

INPUT

A

or

external

INPUT

B

but

not

inter-

nal

OSC).

The

input

defaults

to

a

100

k

ohm

input

impedance.

By

pushing

the

SHIFT

key

and

the

INPUT

TERMINATION

button,

a

600

or

150

ohm

input

termination

may

be

selected.

Two

independent

operations

happen

when

600

or

150

is

selected:

if

(external)

INPUT

A

or

B

is

selected,

a

physical

termination

resis-

tor

is

placed

across

this

selected

input

and

secondly,

the

dBm

reference

impedance

used

to

calculate

the

dBm

reading

is

set

to

600

or

150

ohms,

as

required.

This

im-

pedance

reference

will

remain

until

either

changed

by

Special

Function

26

or

a

new

input

termination

is

selected.

Note

that

selecting

100

k

ohms

will

remove

the

input

termination

but

retain

the

last

used

(600

or

150)

impedance

for

the

dBm

reference.

To

illustrate,

using

an

example:

if

an

external

source

of

0.775

V

open

circuit

and

600

ohm

source

impedance

is

connected

to

INPUT

A,

the

LEVEL

mode

will

indicate

0

dBm

in

the

100

k

ohm

mode,

-6

dBm

in

the

600

ohm

mode

and

-7.96

dBm

in

the

150

ohm

mode.

Again

note

that

the

physical

termination

resistors

only

affect

the

INPUT

A

or

INPUT

B

extemal

sources.

The

intemal

OSC

connec-

tion

cannot

be

terminated

(except

of

course

by

using

an

external

cable

between

GENER-

ATOR

OUTPUT

and

analyzer

INPUT).

2-10

F

L/

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