Rohde & Schwarz ZPV - Continuous Measurement; Measurement of Group Delay Difference

d)
Press
button
SET f
+ 40
kHz
37,
SET f
+
4 kHz
32.
or SET f
Q
+
oA mz
4l
in
accordance
with
the
frequency
increase.
e) The
test
result
is
indicated
on
readout 12;
for
a new
measurement
start
with
a)
.
Since
the
accuracy
of
the
frequency
increase
directly
influences
the
test
result,
the
signal
generator
should
be
checked,
if
required,
using
a
frequency
comter
.
2.3.
4.2
Continuous
Measurement
Pressing
button
T
34
conditions
the
group
delay
measurement.
Button
AUTO
38
permits
selection of
the
automatic
continuous
measurement
mode.
For
automatic
continuous
measurements
the
output
CONTR.
AF
51
of
the
ZPV
is
connected
to
the M-DC
input
of a
generator.
As
with
individual
measurements,
the
phases
of two
very
closely
spaced
frequencies
are
measured
and
the
group
delay is
calculated
from
the
phase
and
the
frequency
differences.
However,
the
generator
frequency
is
automatically
varied
with
the
aid
of
the ZPV.
This
facilitates
operation
considerably.
The
frequency
variation
of
0.4
kHz,
4 kHz
or 40
kHz is
determined
by
pressing
buttons
SET f.
+
0.4
kHz
41,
SET f
+
4 kHz
39
or
SET f
+ 40
kHz
37.
The
Af
setting
also
fixes
the
3
Q
O
corresponding
measurement
range
(see
2.
3 .4.1).
After
connecting
the ZPV
to the
signal
generator,
the
Af
voltage
should
be
matched
by
calibrating
the
slope of
the
generator
modulation
characteristic.
To
this
effect
the test
item
is
replaced
by
the
supplied
calibrating
cable
and
button
CAL.
35
is Pressed.
The
ZPV
performs
the
calibration
automatically,
extinguishing
button
35
upon
termination.
The
linearity
and
frequency
independence
of
the
generator
modulation
character
istic
are
essential
for the
accuracy
of
the
test
results.
The
modulation
sensitivity
of
the
generator
should
always
be
in
the
range
1
V/10
kHz
to
2.5
V/10
kHz.
2.
3.
4.
3
Measurement
of Group
Delay
Difference
Pressing
button AT
36
conditions
the
measurement
of the
group
delay
differ-
ence
relative to
a
reference
delay
both
for
the
single
arid
the
continuous
modes.
Sections
2.
3
.
4.1 and
2.3.
4. 2
apply
accordingly.
The
reference group
delay is
the
value
at
which
button
f
,
T REF.
STORE
11_
is
pressed.
For the
basic
setting
the
reference
delay is
0
ps.
R
36737
-
15