Rohde & Schwarz ZPV - Page 34

2,5.4.
1
Hints
for
the
Adjustment
of
the
Po
tentiometers
PI
and
P2
Using a.
controller.
The
adjustment
is
best
made
during
operation,
i.e.
when
measuring
on
a
crystal.
If
the
control
amplifier
is
not
correctly
adjusted,
the
control
loop
locks
not
exactly
at
0°
but,
for
example,
at
1.3
•
Adjustment
-
Adjust
the
potentiometer
P2
(Fig.
1)
so
that
the
control
loop
locks
exactly
at
0°.
-
Program
a
phase
offset
of
45°.
The
control
loop
will
now
lock
not
exactly
at
45°
but,
for
example,
at
46°.
-
Adjust
PI
for
4.5°.
-
Program
a
phase
offset
of
0°
and
adjust
P2
again
for
0
.
Repeat
this
alternate
adjustment
until
the
control
loop
locks
exactly
at
both
45°
and
0°.
Without
a
controller
If no
computer
is
available,
proceed
as
follows:
-
Switch
the
ZFV
off
and
back
on
again.
Select
the
B/Y
LIN/REF
AUTO
mode.
-
Shortcircuit
the
SWEEP <P
input
of
the
control
amplifier.
-
Connect
the
CONTR
AF
input
of
the
control
amplifier
to
the
CONTR
AF
output
of
the
ZFV.
-
The
voltage
at
this
output
is
now 5.0
V.
_
Vary
P2
until
the
voltage
at
the
output
of
the
control
amplifier
is
0
V.
-
Remove
the
shortcircuit
at
the
SWEEP
^
input
and
connect
the
input
to
the
SWEEP
(f
output
of
the
ZFV.
-
Produce
a
phase
shift
of
about
45°
(watch
the
display
on
the
ZPV),
for
example,
by
interconnecting
the
Group-delay
cable
292.4000.00
(accessory
supplied
with
the
ZFV)
at a
frequency
of
about
2.5
MHz.
-
Press
the
button
STOP
AUTORANGING
FREQ.
;
the
associated
lamp
lights
up.
-
Adjust
the
output
voltage
of
the
control
amplifier
to
0
V by means
of
PI.
R 38535
-
31