TM 11-6625-2724-12
meter with 8 decade ranges from 100 uv full scale to
1000 volts full scale (zero center). The 100 microvolt
The 11 volt power supply is the dc voltage reference
range is not directly selectable on the front panel,
for the (entire voltmeter. The reference element is a
but is used to achieve .001 percent resolution on the
temperuture compensated zener diode in an oven. A
10 volt and up ac ranges. A combination of the
reguluted power supply provides current to the zener
RANGE and NULL SENS switch settings deter-
diode. The 11 volt output is connected to the
mines the effective null range, which is displayed on
RANGE switch.
the front panel.
5-8. MODE Switch
The 1.1 volt resistive divider divides the 11 volt
The MODE switch connects the INPUT to the
reference by 10 for use on the 1 volt and ac ranges.
appropriate assembly for measurement. In the dc
The 1.1 volt output is connected to the RANGE
function, the dialed output of the Kelvin-Varley
switch.
voltage divider is connected in opposing series to the
input unknown voltage. The difference between
The 110 and 1100 volt power supply is a transistor
these two voltages is displayed on the null meter.
regulated power supply which uses the 11 volts as a
W h e n the Kelvin-Varley output voltage (as
reference and provides a 110 and 1100 volt output.
displayed on the decade dials) is exactly the same as
These outputs are connected to the RANGE switch.
the input voltage, the null meter will read zero.
5-5. RANGE Switch
The RANGE switch selects the corresponding power
The ac-dc converter converts the unknown input (if
supply on the dc ranges and the 1.1 volt power
ac) to its equivalent rms value in dc. The ac-dc
supply on all the ac ranges. The RANGE switch
converter always has a 1.1 volt output at full range.
works in conjunction with the NULL SENS switch
An input attenuator is used to attenuate the input
to provide the proper null ranges.
signal on the 10, 100, and 1000 volt ranges.
The Kelvin-Varley divider consists of the three
The recorder output circuit isolates the null detector
decade and vernier control. It divides whichever
meter output voltage and transfers it to the
voltage is selected by the RANGE switch by the
RECORDER OUTPUT terminals on the rear panel.
number (less than unity) to which it is set.
5-7. Null Detector
The null detector is actually a transistorized volt-
