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SECTION
8
MAINTENANCE
6.1 INTRODUCTION
This section contains
information
necessary
to maintain
the
Model 192 DMM
and the Model
1910 AC voltage
option.
Adjustment/calibration,
troubleshooting,
and fuse replace-
ment
procedures
are
provided.
Calibration
should
be
performed
yearly
(every
12 months),
or whenever
perfor-
mances verification
(see Section 61 indicates
that the Model
192 is out of specification.
If any step in the calibration
pro-
cedure
cannot
be performed
properly.
refer
to trouble-
shooting
information
in this section or contact your Keithley
representative
or the factory.
Complete
calibration
and
maintenance
information
for the Model 1920 and the Model
1923 is provided
in the instruction
manual supplied with the
option.
8.2 CALIBRATION
The following
paragraphs
explain
the calibration
procedure
for the Model 192.
WARNING
This procedure
requires
the use of high
voltage
end is Intended
for qualified
test
personnel
only.
Take
care
to
prevent
contact
with
live
circuits
which
could
ceuse electrical
shock
resulting
in injury
or death.
8.2.1 RECOMMENDED
TEST
EQUIPMENT
Recommended
test equipment
for calibration
is listed in
Table 6-l. Alternate
test equipment
may be used, However,
the accuracy
of the alternate
test equipment
must be equal
to the specifications
in Table 8-1,
8.2.2 ENVIRONMENTAL
CONDITIONS
Calibration
should
be performed
under
laboratory
condo-
tions having an ambient temperature
of 23'X
+ l°C. and a
relative
humidity
of less than 70%.
If the instrument
has
been subjected
to temperatures
outside of this range, or to
higher
humidity,
allow one hour minimum
for the instru-
ment to stabilize
st the specified
environmental
conditions
before beginning
the calibration
procedure.
6.2.3 Warm
Up
Connect
the line cord to an appropriate
power source lsee
paragraph
6.3.21 and depress OFF/ON
push button to ON.
Allow two hours for warm up before beginning
the calibra-
tion adjustments.
8.2.4 Calibration
Adjustments
WARNING
Some
procedures
require
the
use
of
high voltage.
Take
cere to prevent
con-
tact with
live circuits
which
could
cause
electrical
shock
resulting
in injury
or
death.
Use
an
insulated
tool
when
making
adjustments.
To make calibration
adjustments:
1. Apply
the appropriate
input.
2. Lift
off the top cover
MOMENTARILY
to make
the
adjustment.
3. When the adjustment
is made reinstall the top cover.
Table
El.
Recommended
Test Equipment
for Calibration
ITEM
A
s
C
D
E
DESCRIPTION
DC Calibrator
AC Calibrator
High Voltage
Amplifier
(Used with Model 745Al
Decade Resistor
Kelvin-Varley
Voltage
Divider
(Used with Model 343A)
SPECIFICATION
19v. 19ov. 1ooov
@20oom
iv,
ibv,
ioov
220ppm
1OOOV. 400ppm
190fl. l.SkQ,
190k0
1.9Mg.
1OMR
Certified
to 50ppm
O.lSV,
l.SV
with 2ppm
Terminal
Linearity
MFR.
Fluke
H-P
H-P
ESI
Fluke
MODEL
343A
745A
746A
RS725
720A
6-l
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