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DC NULL
VOLTMETER
hp
419A
Section V
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209A-B-I662
THERMAL
CONVERTER
hp
H08-II049A
BUCKING SUPPLY
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Mode1209A
Figure 5-2. Flatness Check
b. Set the Model 209A RANGE switch to
XlOO and the frequency dial to 10. Set the
AMPLITUDE control to maximum output.
c. Adjust the BUCKING SUPPLY 50 ohm fine
control for minimum resistance, and record
the THERMAL CONVERTER output as
indicated on the DC NULL VOLTMETER.
the DC NULL VOLTMETER indication by
the
THERMAL
CONVERTER output
voltage recorded in step c of this paragraph.
Multiply this value by 100 to get percent of
output change. Divide this percentage by the
THERMAL CONVERTER multiplier to
obtain a percentage within the tolerances
listed in Table 5-3.
d. Adjust the BUCKING SUPPLY coarse and
fine controls for a OV indication on the DC
NULL VOLTMETER. Do not readjust the
BUCKING
SUPPLY
controls
for
the
remainder of this check.
e. Check the Model 209A flatness at the
frequencies listed in Table 5-3, recording the
DC NULL VOLTMETER indication for each
frequency.
Example:
Frequency
THERMAL CONVERTER output
DC NULL VOLTMETER reading
Calibration Report multiplier
Table 5-3 tolerance
.025 mV x 100%
=
0.29%
5 mV
x
1.7
100 kHz
5mV
25 uV
1.7
+/-0.5%
5-2
NOTE
The THERMAL CONVERTER is
considered a square-law device.
Therefore,
theoretically,
the
percent of change at the output of
the
THERMAL
CONVERTER
should be 2 times the percent of
change at the input. Actually the
value is not quite 2. The number is
typically 1.7. The multiplier (M)
can be determined by measuring
the output (Ei) for a given input,
doubling
the
input and again
measuring the output (EF). The
multiplier is then determined by
the following formula:
M
=
EF/2Ei
f. Convert each reading on the DC NULL
VOLTMETER to the percentages listed in
Table 5-3 by the following procedure. Divide
Table 5-3. Flatness Check
Frequency
Toleran~e
Dial
RANGE
NORM
LOW
Setting
Setting
mST.
2.5
X2
+5% -1%
+/-1%
10
X2
+5% -1%
+/-1%
2.5
X10
+5% -1%
+/-1%
10
X10
+/-0.5%
2.5
X100
+/-0.5%
10
X100
SET
2.5
XlK
+/-0.5%
10
X1K
+/-0.5%
2.5
XlOK
+/-0.5%
10
XlOK
+/-0.5%
3
XlOOK
+/-0.5%
10
X100K
+/-1 %
20
X100K
+/-5%
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