HP 400E, Operating And Service Manual

Page: 28 / 57

Section V
c. Using the null voltmeter, adjust the
reference supply until its output is within
± 1.5 microvolts of the thermal converter
output.
5-18. 3 Volt and 1 V olt Accuracy Test.
5-19. Check the 400E/EL accuracy and frequency
response on the 3 volt and 1 volt ranges according to
the following steps.
5-6
S E T T E S T O S C I LLA TOR
OUTPUT TO MINIMUM BEFORE
C O N N E C TING . R E D U C E
OSCILLA TOR OUTPUT BEFORE
C H A NGI NG F R EQU EN C Y
RANGE. DO NOT A LLOW
OSCI LLATOR O UTPUT TO
EXCEED RATED INPUT OF
THERMAL CONVERTER. ANY
OVERLOAD MAY DESTROY
THERMAL CONVERTER.
a. Set switch Sl in Figure 5-2 to position B,
connecting the test oscillator's 600 ohm
output to the thermal converter input.
Connect the digital voltmeter to the
400E/EL DC OUTPUT terminals.
b. Set the 400E/EL Range Switch to
3
volts
and set the oscillator frequency to 10Hz.
Connect the BNC "T" connector directly to
the 400E/EL INPUT.
c. Using the oscillator amplitude control as
coarse adjustment and resistor R4 (Figure
5-2) as fine adjustment, increase the
oscillator amplitude until the thermal
converter output nulls the reference supply.
Observe the 400E/EL meter indication and
dc output.
d. Repeat step c for each frequency listed in
Table 5-2 . If the 400E/EL
is
within
specifications, the meter indication and the
dc output will be within the tolerances listed
in Table 5- 2.
e. Recalibrate the IOmV reference supply
according to the procedure in Paragraph
5-1 7 using a 1 volt thermal converter and a 1
volt output from the dc standard.
Models 400E/400EL
f. Repeat steps a through d in this paragraph
using the one volt thermal converter and the
50 ohm output of the test oscillator. Set the
400E/EL to the 1 volt range.
5·20. Range Tracking Test.
5-21 . The range tracking test checks the accuracy of
the 400E/EL with a 1/3 scale input over its entire
frequency range.
5-22. After verifying the full scale calibration with
the accuracy test in Paragraph 5-19, check the range
tracking with the following procedures.
a. Recalibrate the IOmV reference supply
according to the procedure in Paragraph
5-17. Use a 600 ohm input, 3 volt thermal
converter and 3 volt output from the dc
standard.
S E T T E S T O S C I LLATOR
OUTPUT TO MINIMUM BEFORE
C O N N E C TI NG .
R E D U C E
OSCILLATOR OUTPUT BEFORE
C H A NGI NG
F R EQU E N C Y
RANGE. DO N O T A LLOW
OSCI LLATOR OUTP U T TO
EXCEED RATED INPUT OF
THERMAL CONVERTER. ANY
OVER LOA D MAY DESTROY
THERMAL CONVERTER.
b. Set SI in Figure 5·2 to position B,
connecting the test oscillator 600 ohm
output to the thermal converter input.
Connect the digital voltmeter to the
400E/EL
OC
OUTPUT terminals.
c. Set the 400E/EL switch to 10 volts and the
oscillator to 10Hz. Connect the BNC "T"
connector directly to the 400E/EL INPUT.
d. Using the oscillator amplitude control as
coarse adjustment and resistor R4
as
a fine
adjustment, set the oscillator output so that
the thermal converter output nulls the
reference supply output.
e. Repeat step d for each frequency listed in
Table 5-2. If the 400E/EL is within
specifications, the meter indication
and
the
dc output will be within the tolerances listed
in the table.