HP 400E, Operating And Service Manual

Page: 24 / 57

Section V
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Models 400E/400EL
MULTI-FUNCTION METER
Figure 5-1. Accuracy Test Setup
c. Set the error range to Xl and turn the
marker to zero position. Read the de output
on the digital voltmeter. The dc output
should read within the tolerances listed in
Table 5-2. With some test setups, it may be
necessary to connect a 500 microfarad capa­
citor across the 400E/EL output to obtain
the requifed resolution at 10 Hz.
d. Adjust the 745A error control until the
400E/EL reads exactly the applied voltage.
Read the 400E/E L error directly
in
% from
the 745A. Where the meter error exceeds
±
3 %, return the 745 A error control to
zero, bring the 400E/EL to the required
reading with the 745A voltage controls and
calculate the error. Any error should be
within the tolerance I isted in Table 5-2
under Meter.
e. Repeat steps c and d for each 745A fre·
quency and voltage listed in Table 5-2 and
5·3 . Connect the precision 40 dB attenuator
between the 745A and the 400E/EL to
calibrate the
I
mV and 3 mV ranges. If the
400E/EL is not within the tolerances l isted
in Table 5-2 and 5-3 refer to Paragraph 5-32
Alignment and Calibration Procedure.
5-13.
Frequ ency Response Check from
110kHz to
10MHz.
5-2
a. For frequencies from 1 10kHz to 10MHz
adjust the 652A (using the 50 ohm output
and a 50 ohm load) to the same reading on
the 400E/EL at 1kHz as read with the 745A.
3 and I volt only can be used on the
expanded scale. (3 and I volt can be
attenuated by the 652A range switch at less
accuracy.)
b. Turn the 652A to the expanded scale and
adjust the REF SET control for 0% or OdB.
c. Change the frequency to those in Table 5-2
and 5-3. Adjust the 652A AMPLITUDE
control until 0 is read on the expanded scale
of the meter. The dc output of the 400E/EL
should be within tolerances listed in Table
5-2 or 5-3 for range, voltage and frequency
settings. Change the fine adjust on the 652A
until the 400E/EL meter reads exactly the
voltage applied. Read error on the 652A
Meter. Where the meter error exceeds
±
2.5 %, readjust the 652A AMPLITUDE
control for 0 on the expanded scale of the
meter and read the error on the 400E/EL
The error should be within the tolerances
listed in Table 5·2 and 5·3 for range, voltage
and frequency settings. If ou t of tolerance
refer to Paragraph 5·32 Alignment and
Calibration Procedure.
NOTE
For accuracy of voltage tracking
not listed in Table 5·2 and 5-3 refer
to the Accuracy Graphs Table 5-4.
Obtain the percentage of accuracy
from the specifications Table 1-1.
Select the proper graph for the
percentage of accuracy. Find the
point on the curve for any tracking
point from full scale to less than
1/3 full scale. Horizontally locate
the error in percent of reading.
5-14_
Accuracy Check Using Thermal Converters.
5-15. The test setup in Figure 5-2 uses a thermal
converter with a null circuit to adjust the frequency
response of the test oscillator to within 0.2% over its
entire band. Construct the 0 to I OmV Reference
Supply shown in Figure 5-2 and allow it at least 24
hours to stabilize.