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жө
Model 427A
SECTION
INSTRUCTIONS
OPERATING
3-1.
INTRODUCTION.
3-2.
The Model 427А may be operated ав а дс volt-
meter,
ac voltmeter,
ohmmeter
or dB meter.
This
section contains operating instructions for each mode
of operation.
3-3.
FRONT
AND
REAR
PANEL
DESCRIPTION.
3-4.
Figure 3-1 shows the location of all the Model
427A controls and indicators and explainsthe function
of each.
Тһе Option 01 rear
panel is shown,
Тһе
standard rear panel is blank.
3-5.
OPERATING
INSTRUCTIONS.
NOTE
To obtain maximum
battery life,
set the FUNCTION
switch of OFF
when the instrument is not in use.
3-6.
MECHANICAL
ZERO ADJUSTMENT.
3-7.
Before any measurements
are made,
complete
the Mechanical
Zero Adjustment
inthe following steps.
а.
Be sure instrument
has been off for at least
one minute.
b.
Rotate
Mechanical
Zero
Adjustment
screw
CLOCKWISE
until meter pointer istothe left
of zero and moving upscale toward zero.
c.
Continue to rotate adjustment screw clockwise,
STOP
when needle
is exactly on zero,
If
needle overshoots,
repeat step b.
а.
When
pointer
is exactly
over
zero,
rotate
adjustment screw slightly COUNTERCLOCK-
WISE to relieve tension on suspension.
И
the pointer іпоуев to the left, repeat
whole
procedure,
but make the counterclockwise
rotation less.
3-8.
TURN-ON PROCEDURE.
3-9,
STANDARD
INSTRUMENT,
a,
Rotate the FUNCTION Switch to BATT/1. 5
MIN position,
b.
Тһе meter should read 1. 5 or higher on the
0-3 scale on any range,
indicating that the
battery voltage is 15 volts or higher.
И the
reading is below
1.5,
replace the battery
according to the steps in Paragraph 5-54.
01791-2
Section ІП
3-10.
OPTION 01 INSTRUMENT.
а.
3-11.
а.
b.
с.
е,
3-12.
а.
Select either battery ог line operation withthe
rear panel BATT/LINE
slide switch.
H bat-
tery operation is selected,
check the battery
according to Paragraph 3-9.
If line operation is selected, set the 115/230
slide switch to indicate the proper line volt-
age,
Rotate the FUNCTION switch to the desired
function.
During line operation,
the BATT/
1.5 MIN check position displays the output of
the Option 01 power supply.
The reading
should be 1,5 or higher on the 0-3 scale оп
any range,
indicating
а power
supply
output
of 15 volts or more.
This serves as а соп-
venient check of the Option 01 power supply.
DC MEASUREMENTS.
Rotate
the
FUNCTION
switch
to +DCV
or
-DCV depending on the polarity of the input.
Short the VOLTS
input tothe COM input,
го-
tate RANGE
to 0. 1, and adjustthe DC ZERO/
Өс thumbwheel for zero meter deflection.
Remove
shorting
connection.
Н there
is a
zero offset with COM and VOLTS open, refer
to Paragraph 4-16 and Paragraph 5-30.
Select approximate range of input with RANGE
switch,
DO NOT
APPLY
MORE
THAN
1200 VDC
TO ANY DC RANGE.
Connect
input across
VOLTS
and COM
ter-
minals and read magnitude
of input on meter.
RESISTANCE
MEASUREMENTS.
DAMAGE
ТО 427A INPUT CIR-
CUIT МАҮ RESULT IF DC OR
AC VOLTAGE
IS APPLIED
TO
OHMS TERMINAL.
Rotate the FUNCTION
switch to OHMS.
Selectthe approximate range withthe RANGE
switch; and withthe input terminals open, ай-
just the DC ZERO/Qe
thumbwheel for an =
indication onthe ohms scale.
(Pointer should
rest on the mark just to the left of х).
3-1
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