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J
i
h
9
c
D
J
b
1
412A
Input
'
Resistance
Model 4
12A
5-13. INPUT RESISTANCE CHECK.
a. Connect the Model 412A/AR, dc standard and 10
rnegolim resistor as shown
in
.Figure 5-1.
b.
Set 412A FUNCTION to VOLTS, POLARITY to
+.
c. Adjust
412A
RANGE and dc standard output to
voltages listed in Table 5-3.
A
correct meter
reading in each case verifies the input resistance
where:
Ein
=
Eapplied
[ &&]
Table
5-3.
Input Resistance Checks
100
mV
412A
Meter
Reading (?
1
%)
5.0
mV
22.5
m V
90.9
mV
0.95
V
I O M Q
30
Ma
100
M a
200
M a
Section
V
c. Set ac voltmeter FUNCTION
to
AC
VOLTS,
RANGE to I O
V.
d. Adjust oscillator frequency to
60
Hz,
and adjust
output for an indication of 7.07
V on
ac
voltmeter. This corresponds
to
a
IO V pcak
;IC
noise signal at the
412A
input.
e. The 412A meter rcadingshould be 02
I%(l
minor
division
on
upper scale)..
5-15. ADJUSTMENT AND CALIBRATION PROCEDURE.
5-16.
The following proccdures should bc pcrfornicd only if
it has been determined by the Performance Chccks outlincd
in Paragraph 5-5 that the Model 412A/AR docs not iiicct
specifications.
5-17. CABINET REMOVAL.
a. Disconnect power cord from powcr source.
b. On cabinet model, rcmovc two rctaining scrcws
near center of rear panel. On rack modcl, rciiiovc
three retaining screws
in
rcar of covcr.
c. Slide instrument chassis forward out of cabinct.
5-18. MECHANICAL ADJUSTMENT OF METER ZERO.
5-14. AC
REJECTION
CHECK.
5-19.
If mechanical zero of mctcr is corrcct, pointcr rcsts
over the zero calibration mark on thc nwtcr scalc wlicii
voltmeter as shown in Figure
5-2.
instrument is at normal opcrating tcmpcraturc,
in
its
normal operating position, and turncd
off.
If nicclianical
zero is not corrcct, perform thc following adjuslment
procedure.
a. Connect the Model
412A/AK,
oscillator, and ac
b.
Set 412A FUNCTION to
VOLTS,
POLARITY to
+,
and RANGE to 0.1 V.
-hp-
MODEL 412A
OSCILLATOR
hp
200CD
Figure 5-2.
AC
Rejection Check
001 29-5
5 -3
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