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2.3
OPERATING CONTROLS
The
operating controls
and
electrical
connections
for
the
Model 142
are
shown
in
Figure
2-1.
The
listing
below
discusses
each
control
and
its
function.
1.
Frequency Range/Power Switch
—
This
11 position
switch
selects
the generator
frequency
range.
The
extreme
counter-clockwise
position
is
the
power
off
position.
2.
Frequency
Dial
—
This
is
the
main frequency
control.
The
setting
on
this dial
multiplied
by
the frequency
range
setting
(above) equals the
output frequency
of
the generator.
The
frequency
vernier
(3)
and
the
symmetry
control
(11) also affect
the generator
fre-
quency.
Note
their
effect
in
the
listing
below.
3.
Frequency
Vernier
—
This control allows
precision
control over the
output
frequency.
A
complete
turn
of
this
vernier
is
equivalent to
approximately
one
half
of the smallest
division
on
the
main frequency
dial.
When
in
the
full
clockwise
position
(CAL),
the
set-
tings
on
the
main
dial will
be
accurate.
4.
Frequency Index
—
The
scribe
line
indicates
the
fre-
quency
dial
setting.
The
index
is
illuminated
when
the unit
is
on.
5.
Waveform
Selector
—
This
selects
the
waveform
that
appears
at
the 50f2
output
connector.
The
waveforms
are
sine
\/
triangle
\
square
Hj
positive
going
pulse
and
negative going
pulse.
6.
Amplitude
Vernier
—
A
vernier control
of the
output
amplitude.
Maximum
clockwise
position gives the
full
output amplitude
of
30
V
peak-to-peak
into
an
open
circuit
or
15
V
p-p into
a
50L2
load,
except
positive
and
negative pulse
which
are 7.5
V
zero-peak
ampli-
tude
into
50J2
load.
Counter-clockwise
rotation
will
continuously reduce the output amplitude.
The
con-
trol
gives a
minimum
of
20
dB
variation (10:
1 ).
This
control
operates
in
conjunction with the
output
atten-
uator
(9).
For
maximum
amplitude output
this
vernier
must
be
full
clockwise
and
the
output
attenuator
in
the
"0
dB"
position.
7.
Sync Out
—
This
output
provides
a
square
or
rectan-
gular
output
at
the
same
frequency
of the
main
generator.
The
output amplitude
is
approximately
2
V
p-p
into 50^2.
The
phase
relationship
between
the
sync
output and
the
waveforms from
the
50^2 output
is
as
shown
in
Figure 2-3
8.
50f2
Out
—
This connector provides the
selected
generator
output
function.
The
generator
may
oper-
ate into
an
open
circuit
providing
30
V
peak-to-peak
maximum,
or
into a
500
load providing
a
15
V
peak-to-peak output.
9.
Output
Attenuator
—
Attenuates
the
output from
0
dB
(15
V
p-p
500
max)
to
—60
dB
(15
mV
p-p
into
500)
in six,
10
dB
steps.
The
vernier
(6)
adds
an
additional
—20
dB,
thus,
a
maximum
of
—80
dB
(1.5
mV
p-p
into
500).
10.
DC
Offset Control
—
This
coaxial
switch controls
the
amount
of
dc
or baseline
offset
above
(-I-)
or
below (—
)
signal
ground.
The
larger
knob
controls
the polarity of
dc
offset
and
the smaller
knob
controls
the
amount
of
offset.
11.
Symmetry
Control
—
This controls the
time sym-
metry between
the
positive
and
negative portions of
the
output waveform.
In
the
full
counter-clockwise
(detent)
position, the control
is
disabled
and
the
output
waveform
has
1:1
symmetry (50%
duty
cycle).
Rotating
the
dial
clockwise
will
vary the
symmetry
from
1:19 through
19:1.
Note:
When
the
symmetry
is
off the
NORM
(detent) position the out-
put frequency
is
divided
by
approximately
a
factor
of
10.
This allows
a
minimum
pulse
width
of
50
nano-
seconds.
12.
VCG
(Voltage Controlled Generator) Input
—
This
connector
allows external control of frequency.
With
0
volts
in,
the generator
output frequency
is
deter-
mined by
the
frequency
range
selected
and
the
fre-
quency
dial
setting.
A
positive
VCG
voltage
will
increase
this
frequency,
and
a negative voltage
will
decrease the frequency. Input
impedance
is
5
kJ2.
13.
External
DC
Offset
—
This connector provides
exter-
nal
control of
dc
level.
This control
only
operates
when
the
dc
offset
switch
is
in
the
0
position.
Maxi-
mum
range
is
±15
V
dc and
sensitivity
is
approxi-
mately
—0.4
volts offset
per
volt input.
2.4
INSTALLATION CHECKS
This paragraph
outlines
a
quick
checkout procedure
to
determine
if
the instrument
is
operating properly.
Field
calibration
and checkout
instructions are given
in
Section
4
to
determine compliance with
electrical
specifications.
If
electrical
deficiencies
exist,
refer
to
the
warranty on
the
back
of the
title
page.
Use
a
Tektronix
Model
454
oscilloscope
(or
equivalent)
and
a
Monsanto Model
101A
Counter-Timer
(or
equivalent)
when
performing
these
installation
checks.
2-2
7/71
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