HP 8508A - Page 31

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Operation
HOLD
VALUE
y
This
retains
the
displayed
values
when
the
signal
voltage
crosses
a
fixed
threshold
or
if
the
instrument
loses
lock.
If
both
displays
are
active,
the
function
is
associated
with
the
B
signal
level.
If
only
the
A
voltage
is
displayed
(Channel
B
is
unused),
the
function
is
associated
with
the
A
channel.
When
the
function
is
engaged,
the
LED
beside
the
key
flashes
to
show
that
a
reading
is
being
held.
CAL
TEST
a
When
[CAL
TEST]
is
selected,
the
instrument
performs
its
power-on
self-checks
and
an
internal
calibration
cycle.
If
an
error
number
is
displayed,
or
if
the
HP
8508A
continues
to
display
a
*tSt’
message,
refer
to
the
Troubleshooting
section
in
Section
8
(Service).
METER
SELECT
This
key
is
used
to
associate
the
METER
with
either
Display
1
or
Display
2,
or
to
turn
it
off.
If
phase
is
being
displayed
in
Display
2,
a
HI
or
LO
annunciator
lights
to
show
the
meter
range.
PROBE
POWER
ie
This
output
provides
+12V
supplies,
which
is
sufficient
to
drive
an
HP
85024A
High
Frequency
Probe.
TEST OUT
This
output
provides
a
signal
at
approximately
1.6MHz
and
150mV
to
allow
the
user
to
check
that
the
HP
8508A
Vector
Voltmeter
is
operating.
The
signal
is
controlled
by
the
[SHIFT]
[CAL
TEST]
function.
The
LED
beside
the
connector
is
on
when
the
test
output
is
enabled.
E1089
3-7