d. Steps a and b are repeated.
4.
To operate the Model 845AR as a High
Impedance Voltmeter,
the
preliminary operations according to paragraph
2 are performed and
the
following procedures would be followed:
a. The controls are placed as follows:
POWER
ON
OPR/ZERO
OPR
RANGE
1000 VOLTS
NOTE
When measuring voltages in the microvolt ranges,
copper wire having low thermal EMFs is used.
b. The voltage to be measured is connected to the Model 845AR INPUT
terminal and the common point of the voltage being measured is connected to
the COMMON terminal.
c. Deflection of the meter indicates the polarity and magnitude of the
measured voltage.
The sensitivity of the Model 845AR is increased for
maximum on-scale deflection.
5.
The Model 845AR may be used to monitor small voltage differences in
bridge circuits, potentiometers, and other measuring apparatus. In most of
these applications the circuits are adjusted for zero deflection or a null
on the Model 845AR.
Equipment connections for various types of null
detector configurations are illustrated by Figures 4-2 through 4-4.
To
operate the Model 845AR as a null detector, perform the preliminary
operations according to paragraph 2 are performed and the following
procedure would be followed:
a. The desired equipment application is selected as illustrated by
Figures 4-2 through 4-4 and the appropriate equipment connections are made.
b. The Model 845AR controls are placed as follows:
POWER
ON
OPR/ZERO
OPR
RANGE
as desired
c. The circuit being measured is adjusted for zero or a null deflection
on the Model 845AR meter.
73
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