Keithley 486 Instruction Manual page 159

SECTION 7
Maintenance
Table 7-2. Calibration Equipment
Model
263
6171
7024-3
197
1973
B-24
Description I Specification
Calibrator/Source (5-l/2 digits) 2nA, 2onA ranges: f(0.065% + 10 counts)
2oonA range: f(0.035% + 10 counts)
3slot male to 2-Q female i&ix
adapter
2@-2mA ranges: i(O.O25% + 10 counts)
-
2slot triax cable
-
DMYh4 (DC Volts) (5-l/2 digits)
IEEE-488 Interface for Model 197
2OOV, 1OOOV ranges: +(0.015% + 2 counts)
-
Banana Plug Cable (2 required)
-
*Items A, B and C are used to calibrate
the picoammeter of the Models 486 and 487.
**Items 0, E and Fare used to calibrate the voltage source of the Model 437. Note that item E (Model 1973) is only required if you wish to cm-
trol the
Model
197
DMM aver the IEEE-488 bus.
7.3.2 Environmental Conditions
Calibration should be performed under laboratory con-
ditions having an ambient temperature of 23°C HOC and
a reiative humidity of less than 70%.
7.3.3
CAL LOCK Switch
A CAL LOCK switch, accessible from the rear panel (see
Figure 7-Q disables or enables calibration. When calibra-
tion is disabled (switch in "out" position), calibration
cannot be performed. The following message will be
briefly displayed when attempting to calibrate the instru-
ment while the switch is in the disabled position.
CAL LOCKED
Calibration can only be accomplished with the calibra-
tion switch in the enabled position.
WARNING
To avoid electric shock, hum the instrument
off and disconnect the line cord before oper-
ating the CAL LOCK switch.
To enable calibration, push in the CAL LOCK switch to
the "in" position using an INSULATED tool (through the
small access hole in the rear panel).
After calibration is complete, again press the CAL LOCK
switch to place it in the "out" position to disable &bra-
lion.
7-2
3
Calibration Switch
(sticker covers access hole)
In = Calibration enabled
Out = Calibration disabled
Ygure 7-l. Cal Lock Switch
7.3.4
Warm-Up Period
Turn on the insinunent power and allow it to warm up
for at least two hours before beginning the calibration
procedure. If the instrument has been subjected to ex-
tremes of temperature or humidity, allow at least one ad-
ditional hour for the instrument to stabilize before begin-
ning the calibration procedure.
7.3.5
Front Panel Calibration
Pica-eter Calibration
In general, current calibration
consists
of applying a
source value of +190,000 counts to each range and per-
forming the calibration routine. Table 7-3 lists the re-
quired calibration current for each range. For front panel