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MAINTENANCE
Table 7-3. Recommended
Calibration
Equipment
7.5.3 Warm-up
Period
To ensure long-term
accuracy, turn on the power to the
Model 194 and allow it to warm up for at least axe hour
before beginning
the calibration
procedure.
7.5.4 Front
Panel Calibration
Front panel calibration of the instrument
involves connect-
ing a precise DC voltage calibration
source to the instru-
ment and then entering the front panel calibration
pro-
gram. A general flow chart of the procedure is shown in
Figure 7-3. Note that those ranges not calibrated by this
procedure will retain former calibration.
CAUTION
The
maximum
input
voltage
is 250V peak,
2 x
iOY*Hz.
1. Connect the DC calibrator to the VOLTAGE INPUT jack
of the A/D module being calibrated, as shown in Figure
74.
2. Select the channel to be calibrated with the CHANNEL
button.
NOTE
The necessary operating
parameters
are auto-
matically
selected by the instrument.
3. Place the Model 194 on the 32OmV rawze.
4. Set the DC calibrator to the value in the first line of Table
7-4 (32O.OOmV).
5. Enter the front panel calibration
program by pressing
OTHER and using uprange until
the DIGITAL
CAL
message is shown. Press ENTER. The presently selected
calibration
value will be displayed
6. Key in a value of 320.00rnV with the data entry keys XXI
press ENTER. The unit will then perform LUO and e>in
calibration,
a process that will take a number of seconds
to complete. If gain or zero cannot be pcriormcd
prop-
erly the appropriate
message will bc displayed.
CAN'T CAL GAIN
or
CAN'T CAL ZERO
If calibration of the presently se&cd
range is wcccssiul,
the following
message will be displ,~yed:
CALIURAI'ION
OK
7, Repeat steps 3 through
6 abovc for the 3.2V, 32V, ami
200V ranges. The correct calibration
voltages end pre
gram parameters xc listed in Table 7-4
8. Repeat the above procedure
for the channel
7 :\ D
module,
if installed.
9. Press OTHER,
uprangc
(three times) axi
I-'""'
tht,
E:NTER key to enter the NVRAM stor.lg,t? prugrx".
l'rc'ss
the ENTER key to permanently
store calibration.
Sate
that this last step is necessary to permanently
store
calibration
parameters in NVRAM.
Table 7-4. Calibration
Summary
7-7
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