HP 652A Operating And Service Manual page 22

percentage the ac input changes. Typically. it
changes 1. 7 times. When making response
measurements, the transfer characteristics of
your particular thermal converter should be
used. To determine the thermal transfer char­
acteristic of your particular thermal converter,
proceed as f ollows:
1. Set the 652A output amplitude to mini­
mum
2. Connect the 11049A Thermal Converter
directl y to the 50 n output of the 652A.
3. Connect the 419A DC Nullmeter across
the dc output of the Thermal Converter.
4. Adjust the 652A output amplitude con­
trol for 1 V rms input to the Thermal Con­
verter (use an ac voltmeter to monitor the ac
input to the Thermal Converter).
5. Measure and record the dc output (Ed
of the Thermal Converter on the 419A.
6. Double the ac input to 2 V rms. Again.
observe the null meter and record the reading
(E f ).
7.
Calculate the transfer ratio as follows:
Trans f er characteristic (k)
Table 5-3 assumes a transfer ratio of 2.
The actual transfer ratio of your Ther­
mal Converter should be applied to
Table 5-3 as follows:
DC CHANGE the percentage of ac
=
ON 419A
change
times the transfer ratio.
For example, if the trans fer ratio of
your Thermal Converter is 1. 7, a 1%
TEST OSCILLATOR
hp652A
652A-e-08SM
--L
E
=
2 E i
times 7 m V
THERM AL CONVERTER
I
I hp I I049A
i
,------------
Figure 5�3. Flatness Tests.
Table 5-3_ Typical Thermal Converter Input/Output Change.
CHANGE AT
AC INPUT OF
THERMAL CONVERTER
+/- 0.25%
+/- 1 %
+/- 2%
+/- 3%
+/- 4%
The ac input is set for 7.0 m V at the output
of the thermal converter.
change in the ac input (Table 5-3) would
result in 70 llV (change in ac input)
times 1. 7 (transfer ratio)
a. Connect equipment as shown in Figure 5-3_ (Use a
thermal converter with a known change in output for a
given change at the input. If this information is not readily
available. then Table 5-3 gives this information for a typical
thermal converter connected as in Figure 5-3). Set both
652A output and reference supply to minimum before
connecting. Thermal converter must be connected directly
to 50 ohm output of 652A_
Do not exceed rated input of thermal con­
verter. A ny overload or high voltage transient
may destroy thermoelement. When using the
652A FREQU ENCY RANGE switch. momen­
tarily turn down the output attenuator.
b. Set 652A controls as follows:
FREQUENCY RANGE
FREQUENCY dial
. • • . _ • • • . • . • • • . . • .
OUTPUT ATTENUATOR
OUTPUT MONITOR . _ _ . _ . _ . _ . _ .NORMAL
DC NULL
VOLTMETER
hp 4 1 9A
REFERENCE SUPPLY
r - - - - - - - -- ------
I
I
I
I
I
I
I
I
I
1
1
�
CHANGE OF DC
NULL METER
INDICATION FROM
NULL SETTING
+/- 35 microvolts
+/- 140 microvolts
+/- 280 microvolts
+/- 420 microvolts
+/- 560 microvolts
119 1lV.
=
XI K
. • • • . • . • • . • • . •
"
10
.
3.0 V
. . • • . . • . . .
- - -,
I
I
R I
I
6500n.
I
BTl
R2
1.34V !
500n.
I
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1
I
R3
I
50n
1
1
J
___________ _ _ _ _ _ _
5-3