Table of Contents
Advertisement
MAINTENANCE
7.5.6 Input Amplifier
Frequency
Compensation
Adjustment
The input amplifier
incorporates
two trimmer capacitors
in order to adjust the input
amplifier
for flat response.
These two capacitors are accessible through
the input
amplifier shield, as indicated in Figure 7-5. Use only a non-
metallic alignment
tool when making these adjustments
in order to avoid misadjustment
that could be caused by
tool capacitance.
Proceed as follows:
1. Connect the AC calibrator to the channel being tested
using the connections
shown in Figure 7-6.
2. Select the channel
being tested and the following
operating
modes on the Model 194:
A. Sampling
interval:
1Opsec
8. Samples: 1000
C. Trigger: Continuous
D. Coupling:
AC
E. Math function:
TRMS
F. Filter: Off
6. Trigger Source: Input Signal
H. Trigger Level: OV
3. Select the ZOOV range on the instrument
and disable
zero. Press TRIGGER.
4. Set the calibrator output
to 3O.OOV at a frequency
of
lkH2.
5. Enable the zero mode on the Model 194 (press ZERO).
6. Change the calibrator frequency
to 45kHz, but leave
the output
at 3O.OoV.
7, Adjust C386 on the input amplifier
(Figure 7-5) for a
reading of OOO.OOV *O.ZV on the display.
NOTE
When making adjustments,
allow sufficient
time
for any changes to be reflected in the display.
8. Disable the zer" mode.
9. Set the calibrator output
to lO.OOOV at a frequency
of
IkHz.
10. Change the Model 194 to the 32V range and enable
ZW".
11. Set the calibrator frequency to 45kHz, but leave the "ut-
put voltage at 1,o.ooOV.
12. Adjust C374 on the input amplifier
(Figure 7-5) for a
reading of OO.OOOV *O.OZV on the display.
13. Repeat steps 3 through
12 above to minimize
interac-
tion between the two adjustments.
Table 7-5. AC Response Adjustment
Procedure
Applied
Model 194
Model
194
step
Voltage*
Range
Reading"
Comments
1
30V @ lkHz
2ooV
Zero disabled
2
30V @ 45kHz
2oov
OOO.OOV+O.ZV Zero enabled
3
1OV @ lkHz
32V
-
Zero disabled
4
1OV @ 45kHz
32V
OO.OOOV-tO.02V Zero disabled
*RMS values.
**Appropriate
trimmer
to be adjusted for this reading.
7-10
Advertisement
Table of Contents
