Partial Blocking - BRUEL & KJAER 1022 Instructions And Applications
Beat frequency oscillator
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- Instructions and applications (25 pages) ,
- Instructions and applications (52 pages)
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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
Re
corder
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·
s tance
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•
a ting 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
frequency
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.
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