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H 52005-301D
SETTING OUTPUT IMPEDANCE
30.
The
different
output
impedances
available as
follows arc only obtained
providinl{ the input
to
the
attenuator
comes
from
a
GOO
n generator. or providing a substantial amount of attenuation
is in use (o\·er 13 dB ensures
an
output
impedance close to the selected
nominal value).
31
.
The OUTPUT terminals
contain
sockets
for
4
mm
plugs and any pair of adjacent terminals
will
accept a
twin plug having
19
mm
pin
spacing
.
Carrying a
BNC
socket,
the
shielded adaptor
can be
plugged into the two UNBAL terminals
to
provide good shielding and
facilitate
employing
coaxial
leads.
600 n, 150 nor 75 n balanced
32.
Set the controls
and
connect
the load
as
follows ·-
(1)
Set the OUTPUT
IMPEDANCE
switch
to whichever of the BAL positions
indicates the
required
source
impedance.
(2)
Set the
LOAD
switch to
EXT.
(3)
Connect the
load
to
the
two
BAL terminals.
33.
If the BAL terminals alone are
used,
a
floating source is obtained.
To balance the source
relative
to
earth, connect
the CENTRE TAP
terminal
to earth.
The
left-hand
UNBAL terminal,
which
is
connected internally to case and chassis,
serves
as an earth point assuming that the
outer of the coaxial
inlet
socket on the attenuator
is
earthed by the input
lead.
34.
Under these conditions
the matching transformer
is in use and the frequency range of the
instrument
is
20 Hz to 20 kHz.
600 n unbalanced
35.
Set the controls and connect the load as follows
(1)
Set the OUTPUT
IMPEDANCE
switch to
600
Q
UNBAL.
(2)
Set
the
WAD
switch to EXT.
(3)
Connect the
load
to the
two UNBAL terminals.
The
left-hand
one, which is connected
internally
to case
and
chassis,
serves
as an
earth
point
assuming
that
the
outer
of
the
co-
axial inlet socket on the
a
ttenuator
is earthed
by
the input
lead
.
36.
Under these
conditions
the
output is obtained directly from
the attenuating
networks and the
frequency
range
ofthe instrument
extends
from
d.
c. to
550
kHz (except that the input
voltmeter
becomes inaccurate below
20
Hz).
150
nor
75
Q
unbalanced
37.
Set the controls
and connect
the load as follows :-
(1)
Set the OUTPUT IMPEDANCE
switch
to BAL
150
Q
or BAL
75
n
,
according to
the
required value
of source
impedance.
(2)
Set the LOAD
switch
to EXT.
(3)
Connect
the
load
to the two
BAL terminals
.
Connect one
of these
terminals
to earth,
as required
.
The
left-hand UNBAL
terminal
,
which is
connected internally
to case and
chas
s is,
ser
ves
as an earth point assumi
ng
that the
outer of
the
coaxial
inlet
s
ocket on the
a
ttenuator is
earthed by the
input
lead.
Leave the CENTRE TAP
terminal disconnected.
Nov.
79
Chap
.
3
Page 7
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