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845AR
a.
Place the Model 845AR controls as follows:
POWER
ON
RANGE
10 MICROVOLTS
OPR/ZERO
ZERO
b.
Adjust thezero control for an initial zero meter
deflection.
Place the RANGE
switch to the 1
MICROVOLT
RANGE and re-zero with the zero
control,
2-7,
MECHANICAL ZEROING
2-8,
It may become necéssary to adjust the mechani-
cal zero control of the Model 845AR at more frequent
intervals than complete calibration.
To mechanically
zero the instrument proceed as follows:
a.
Place the RANGE
switch to 1000 VOLTS and the
POWER switch to ON.
b.
Adjust the mechanical zero adjustment screw for
zero meter deflection.
c.
Place the RANGE switch to 10 MICROVOLTS and
electrically zero the instrument
as outlined in
paragraph 2-5.
d.
Repeat steps a and b.
2-9.
OPERATION AS A HIGH
IMPEDANCE
VOLTMETER
2-10.
To operate the Model 845AR as a High Impedance
Voltmeter perform the preliminary operations according
to paragraph 2-5 and proceed as follows:
a.
Place the controls as follows:
POWER
ON
OPR/ZERO
OPR
RANGE
1000 VOLTS
Mote!
When measuring voltages in the microvolt
ranges, use copper wire having low thermal
EMF's.
b.
Connect the voltage to be measured to the Model
845AR INPUT terminal and connect the common
point of the voltage being measured to the COMMON
terminal.
c.
Deflection of the meter indicates the polarity and
magnitude of the measured voltage.
Increase the
sensitivity of the Model 845AR for maximum on-
scale deflection.
2-11,
OPERATION
AS A NULL DETECTOR
2-12.
The Model 845AR may be used to monitor small
voltage differences in bridge circuits,
potentiometers,
and other measuring apparatus.
In most of these appli-
cations the circuits are adjusted for zero deflection or
a null on the Model 845AR.
Equipment connections for
2-2
various types of null detector configurations are illus-
trated by Figure 2-2 through 2-4.
To operate the Model
845AR as a Null Detector, perform the preliminary
operations according to paragraph 2-5 and proceed as
follows:
a.
Select the desired equipment application as illus-
trated by Figure 2-2 through 2-4 and make the
appropriate equipment connections.
b. ' Place the Model 845AR controls as follows:
POWER
ON
OPR/ZERO
OPR
RANGE
as desired
c.
Adjust the circuit being measured for zero or a null
deflection on the Model 845AR meter.
Figure 2-2.
BRIDGE DETECTOR - FLOATING SUPPLY
Figure 2-3.
BRIDGE DETECTOR - HIGH RESISTANCE
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