HP 8508A - Other Functions

Operation
1. Connect the A and B inputs to the bridge or splitter as shown in one of the above diagrams (depending on the
equipment you have available). Set the source power to dBm and frequency to the test frequency.
-2, Connect a short circuit to the test port as the calibration standard. Press [PRESET] to return the HP 8508A to a
known state. Select [REFL MEAS] rho, angle to measure reflection coefficient.
3.
Select
[REF
SELECT]
SHORT
to
use
a
short
circuit
as
the
calibration
standard.
Select
[DISPLAY]
dB
to
measure
the reflection
as
return
loss
in
dB.
Press
[SHIFT]
then
[SAVE
REF]
to
store the-current
measurement
and
display.a
return loss
of
0dB
and
angle
0
degrees.
4,
Remove
the
calibration
standard
and
connect
the
termination
to
be
measured.
Read
the
return
loss
directly.
The
HP
8508A
has
conversions
built
in
to
allow
you
to
read
results
in
normalized
impedance
for
use
with
Smith
.
charts,
To
make
the
conversion,
select
[REFL
MEAS]
Z,
and
[SYSTEM
IMPD]
NORM.
There
is
no
need
to
recalibrate
since the
new
display is
computed
from
the
same
measurements
as
before.
.
c. Other functions
[HOLD
VALUE]
-
This
function
is
useful
when
you
are
probing
in
a
circuit
(especially
dense
circuits
where
the
probe
can
easily
slip
onto
another
track).
When
the
signal
disappears,
the
display
is
frozen
at
the
last
reading.
To
initiate
this
function,
configure
the
equipment
for
the
measurement
you
want
to
make
(A,
B/A,
B).
Now
press
[HOLD
VALUE].
The
LED
at
the
side
of
the
key
will
illuminate.
Probe
on
the
circuit.
(Use
the
A
probe
if
“A”
only
is
active
or
the
B
probe
if
both
are
active.)
Lift
the
probe
when
you
are
ready
to
take
a
reading.
The
display(s)
will freeze
and
hold
the reading.
The
function
LED
will
flash
to
show
that
the
hold
mode is
active.
To make
a new
measurement,
probe
on
the
circuit.
The
instrument
will
automatically
re-arm
the
function.
[REF
SELECT]
LOAD
-
This
function
allows
the
use
of
a
simple
twe
resistor
tee
to
enable
you
to
make
reflection
‘measurements
up
to
100MHiz. In
this
case,
a termination
is
used
as
the
calibration
standard.
Choose LOAD with the following test setup.
Source HP8&508A
908A
a Termination
Power :
Splitter 908A Termination
(Calibration)
Device Under
Test
Probe Tee
Figure 3-14, Probe Inputs
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