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3.4
INITIAL SWITCH AND CONTROL SETTINGS.
Set the various switches and
controls on the front panel of the Model 75D in accordance with the following table.
Table 4.
Initial Switch and Control Settings
COMPONENT
SETTING OR POSITION
CAPACITANCE main dial and vernier dial
CONDUCTANCE G-scale dial
MULTIPLY C switch
DIVIDE G/MULTIPLY R switch
R/G ZERO control
C ZERO FINE and COARSE controls
C/L switch
TEST LEVEL control
GAIN control
PHASE control
Meter switch
DC BIAS switch
DC BIAS INTERNAL ADJUST control
Terminal shield
0
0
Set to appropriate range
Set to appropriate range
1 2 o'clock
1 2 o'clock
C
Fully clockwise
(See Par. 3.5.1 )
Fully clockwise
(See Par. 3.5.2)
1 2 o'clock
ZERO LEFT
OFF
(See Par. 3.5.3)
Fully counterclockwise
Installed on TEST binding
posts
3.5
ZERO-BALANCING THE BRIDGE.
The zero-balance procedure is a basic
operation that is performed during each measurement and test procedure in this
chapter.
Therefore, familiarization with zero-balancing is recommended before
proceeding with the measurements or tests.
During operation, any of the following
conditions will require zero-balancing the bridge:
a.
The setting of the MULTIPLY C switch is changed.
b.
The setting of the DIVIDE G/MULTIPLY R switch is changed.
c.
The setting of the C/L switch is changed.
d.
The position of the GAIN control is changed.
e.
The position of the TEST LEVEL control is changed.
f.
Test leads, cables, or a test jig are connected to the Model 75D.
g. When either the terminal shield or the ground plane adapter
installed on the TEST binding
posts is removed.
Before starting the zero-balancing process which follows, check that no test specimen
is connected to the Model 75D and note the following definitions of a null indication
and a complete null.' A null indication is defined as minimum meter reading.
For a
complete null, the meter pointer must be within one subdivision of zero when the
MULTIPLY C switch is at any position except 1 . When the MULTIPLY C switch is at 1,
the meter pointer must be within three subdivisions of zero for a complete null.
Proceed with the following steps to zero balance the bridge.
75D
b-370
22
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