HP 436A - Page 64

Performance Tests
Model
436A
PERFORMANCE TESTS
4-13.
POWER
REFERENCE
LEVEL
TEST (cont'd)
•
EQUIPMENT:
PROCEDURE:
4-8
POWER
METER
432A
DIGITAL
VOLTMETER
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PO
WEA
REF
THERMISTOR
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OUTPUT
MOUNT
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Figure
4-4.
Power
Reference
Level
Test
Setup
Power
Meter
HP
432A
Thermistor
Mount
.
Digital Voltmeter (DVM).
HP
478A-H75
HP
3456A
1.
Set
up
the
DVM
to
measure resistance and
connect
the
DVM between the
VRF
connector
on
the
rear panel
of
the
432A, and pin 1
on
the
thermistor
mount
end
of
the
432A
interconnect cable.
2.
Round
off
the
DVM indication
to
two
decimal places
and
record this value as
the
internal bridge resistance (R)
of
the 432A (approximately
200
ohms).
3. Connect
the
432A
to
the
Power
Meter
as
shown in Figure 4-4.
4.
Set
the
Power
Meter LINE switch
to
ON
(in)
and
the
POWER
REF
switch
to
off
(out).
Then
wait
thirty
minutes for the
432A
thermistor
mount
to
stabilize
be-
fore proceeding
to
the
next
step.
5.
Set
the
432A
RANGE switch
to
COARSE ZERO
and
adjust
the
front-panel
COARSE ZERO
control
to
obtain a zero
meter
indication.
6. Fine zero
the
432A
on
the
most
sensitive range,
then
set
the 432A RANGE switch
to
1
mW.
NOTE
Ensure that
DVM
input
leads are isolated from chassis
ground when performing the
next
step.
7.
Set
up
the
DVM
to
measure microvolts
and
connect
the
positive and negative
input
leads, respectively,
to
the
V
COMP
and
V
RF
connectors
on
the
rear panel
of
the
432A.
8.
Observe
the
indication on
the
DVM.
If
less
than
400
microvolts, proceed
to
the
next
step.
If
400
microvolts
or
greater, press
and
hold
the
432A FINE
ZERO
switch
and
adjust
the
COARSE ZERO
control
so
that
the
DVM
indicates
200
microvolts
or
less. Then release
the
FINE
ZERO
switch and proceed
to
the
next
step.
•
9.
Round
off
the
DVM
indication
to
the
nearest microvolt and record this value
as
Vo· •