Fluke 341A - Beta String Linearity

341
A
343A
Set
FUNCTION
switch to
METER
CURRENT.
The
Model
341A/343A meter
should
indicate
between
23.7 and 26.3
milliamps.
—
FAULT ANALYSIS
(1)
If voltage
readings are
incorrect
on one
range only, check
corresponding
range
resistor
R71, R72,
R73 or
R74.
If
vol-
tage readings
are
incorrect on
all ranges,
check
meter
Ml and resistors
R44
and
R45.
(2)
If current
readings are
incorrect,
check
current
sensing resistor
R70
and asso-
ciated components.
461. MODEL
341 A
CALIBRATION
4-62.
Calibration
of the
Model
341 A consists of
five
ordered steps:
(1)
reference
voltage
adjustment,
(2)
zero
output adjustment,
(3)
beta string
linearity
adjustments,
(4)
range adjustments,
and
(5)
verification
of calibration.
Before
attempting
calibration,
instrument
performance
should be
examined
according to the
performance tests
in paragraph 4-24
to ensure
that no
malfunctions
exist.
4-63.
PRELIMINARY
OPERATIONS
a. Connect
the
Model
341 A to the
autotransformer,
and adjust the
autotransformer
for
115 volts
output.
b. Set Model
341 A controls as
follows:
FUNCTION
ON
RANGE
10
Voltage
Dials
10.00000
c. Attach
all covers,
and allow
instrument to
operate for
at least
1 hour.
4-64.
REFERENCE
VOLTAGE
ADJUSTMENT
a. Unfasten
the top cover
and slide
back just far
enough
to
expose REF
ADJUST
control R26 and
test point
TP2.
b.
Connect the
895 A differential
voltmeter
to TP2,
using ±
SENSE
as common.
c.
Adjust
R26 for
an
895A indication
of
15 ±0.0001
volts
dc.
i
•
d.
Disconnect the
895
A,
and position
the top
cover
so
that only
the beta
string
calibration
controls
are ex-
posed.
4-65.
ZERO OUTPUT
ADJUSTMENTS
a. Set
Model
341 A voltage
dials to
zero,
and connect
the negative
OUTPUT
terminal
to
chassis
ground.
b. Zero
the
895A on the
1,
volt range,
with
null sensi-
tivity
set to 100
microvolts,
then connect
the
895
A
to the
Model
341 A OUTPUT
terminals
using
low-
thermal
copper leads.
c.
Set RANGE
switch to
10,
and adjust
the
10V
ZERO
ADJUST
control
for zero
(±5
microvolts)
indication
on the
895A.
WARMING!
Use
only an insulated
tool for
all
adjustments
within the
beta string
compartment.
d.
Set RANGE
switch
to
100,
and
adjust
the
100V
ZERO ADJUST
control
for
zero
(±10
microvolts)
indication
on the
895
A
e. Set
RANGE
switch
to
1000,
and
adjust
the
1000V
ZERO ADJUST
control
for
zero
(±10
microvolts)
indication
on
the
895
A.
4-66.
BETA
STRING
LINEARITY
ADJUSTMENTS
a. Set
RANGE switch
to
100, and connect
the
895
A
to the
Model
341 A OUTPUT
terminals,
with
the
Model
341 A
negative
OUTPUT
terminal
connected
to chassis
ground.
b. Set the
Model
341 A controls
as
shown in
Figure 4-10
and perform
the indicated
operations
(step
c. through
step
n.).
4-67.
RANGE
ADJUSTMENTS
a. Connect the
895A
to
the OUTPUT
terminals,
with
the
Model
341 A negative
OUTPUT
terminal
con-
nected to
chassis ground.
b.
Set
the
Model
341 A controls
as
follows:
FUNCTION
ON
RANGE
10
Voltage dials
10.00000