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SECTION 2
BENCH OPERATION
2.1 INTRODUCTION
This section contains the information
needed to prepare and
operate the Model 485 as a bench picoammeter.
Bench
operation consists of using the Model 485 to perform basic
current measurements. Data store operation is also covered.
The capabilities of the Model 485 can be enhanced with the
addition of the Model 4853 IEEE-488 interface. IEEE opers-
tion is covered in the Model 4853 Instruction
Manual.
2.2 PREPARATION
FOR USE
2.2.1 Line Power
The Model 485 is provided with a three-wire line cord which
mates with third-wire
grounded receptacles. Connect the in-
strument to AC line power as follows:
1. Set the LINE VOLTAGE switch on the back of the instru-
ment to correspond to line voltage available. Ranges are
105-125V or 210-250V 50/60Hz AC.
CAUTION
Connect
only to the line voltage selected.
Application
of
incorrect
voltage
can
damage the instrument.
2. Plug the power cord into a properly grounded outlet.
WARNING
Ground the instrument
through
a properly
grounded
receptacle
before
operation.
Failure to ground the instrument
can result
in severe injury or death
in the event
of
short circuit or malfunction.
NOTE
Although the Model 485 is specified at 50Hz and
60Hz the instrument may be operated at 400Hz
and 440Hz.
Add
one count
to
instrument
specifications
under this condition.
2.2.2 Battery Pack Power
The Model 485 may also be operated from rechargeable
sealed nickel-cadmium
batteries contained
in the optional
Model 1758 Rechargeable Battery Pack. The battery pack will
operate the Model 485 for up to six hours. The BAT ennun-
ciator will turn on when the banely charge is insufficient
to
maintain eccurate readings. Refer to Section 5, paragraph 5.3
for installation procedures.
2.2.3 Battery Charging
After the Model 1758 Banery Pack is installed in the Model
485 it can be charged and recharged as follows:
1. Connect the instrument
to line power as described in
paragraph 2.2.1.
2. With the power switch off, the battery charge circuitry is
automatically
energized to charge the battery at the maxi-
mum rate. When the battery pack is first installed, or if it is
completely discharged, allow it to charge for ten hours.
NOTE
For maximum battery efficiency only charge the
battery pack after it has become discharged and
only charge until it is fully charged I,10 hours).
Continuous
charging over long periods of time
will not damage the batteries but, useful life will
gradually decrease. This loss is not permanent
and may be restored by cycling the battery pack
through
several
complete
charge/discharge
cycles. The battery pack is capable of 500 to
1000 charge/discharge
cycles before replace-
ment is needed.
Do not make measurements with the BAT annunciator on as
the readings may be erroneous.
3. When the Model 485 is in use on line power, the banely
charger maintains a trickle charge on the battery pack.
2.3 TILT BAIL
The Model 485 is equipped with a tilt bail which makes it
possible to elevate the instrument
to a convenient
viewing
position. To change the bail position, pull out the bail handle
from each side of the case until it rotates freely; rotate the bail
to the desired position and release the bail to allow it to lock
into place.
2.4 MODEL 485 FAMILIARIZATION
The following
paragraphs and Figure 2-l provides a brief
description of the display, front panel controls and connec-
tors.
2.4.1 Display
The Model 485 has a 4% digit liquid crystal display (LCD).
The minus sign is displayed. The plus sign is implied by the
absence of the minus sign. The following
annunciators
are
displayed on the LCD.
2-l
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