TB 9-6625-133-40
Example for 100:1 divider (100 mV nominal):
Vref = 10.0000720 V dc
R1 = 100.00026 kΩ
R2 = 1.0000011 kΩ
True applied = 99.010467 mV dc
,
.
. 99
4
=
.
,
.
+,
.
c. Record the test report value of the transfer standard 10 V tap (from table A-1) in
row 5 True Applied column in table A-2. Record negative value of the same number in
row 6.
d. Multiply the test report value of the transfer standard 10 V tap (from table A-1) by
10 (i.e., 100.00072). Record this value in the True Applied column in table A-2, row 9.
Record negative value of the same number in row 10.
e. Multiply the test report value of the transfer standard 10 V tap (from table A-1) by
100 (i.e., 1000.0072). Record this value in the True Applied column in table A-2, row 11.
Record negative value of the same number in row 12.
f. ZERO nullmeter by performing (1) through (18) below.
NOTE
Knowing what ranges to zero can greatly reduce procedure
time. It is necessary to zero only the nullmeter ranges that will
be used for final measurements, typically the uV ranges. Note
that 1/3rd scale on the 3 uVolt range (1 uVolt) equates to 0.1
ppm at 10 Volts which is the resolution of the calibrator. The
DC reference divider self calibration requires an accurate
measurement to 0.5 uV. At a minimum, the nullmeter should
be zeroed to accommodate these measurements.
NOTE
It will be difficult, if not impossible, to obtain stability on the
nullmeter with any disturbance near the measurement.
Personnel traffic, drafts, opening and closing of doors, etc.
should all be minimized before attempting a measurement.
NOTE
When the nullmeter OPERATE/ZERO switch is placed in the
ZERO position, the HI input terminal is disconnected and the
input to the internal amplifier is shorted to LO, removing the
nullmeter
from
the
measurement.
Placing
the
OPERATE/ZERO switch in the ZERO position is an effective
method of preventing meter pegging when not in use.
A-3