HP 5065A Manual page 17

I
dt
Figure 3-3. Magnetic Field Control
c. Zero HP 8405A PHASE meter by cranking in
necessary offset with METER OFFSET control and the
red ZERO knob.
d With the meter zeroed, set the RANGE switch
at +6. Recenter the PHASE meter with the red ZERO
knob.
e Set strip chart recorder range to .5 volt. Set
pen to chart scale center with recorder zero controL
f. Set HP 8405A phase range to ±180 and change
METER OFFSET by +180'.
g Adjust 1 Ok ohm pot for full scale pen deflection
on recorder.
h. Change METER OFFSET polarity to (-) using
the center knob of the METER OFFSET CONTROL. Pen
should move to opposite chart edge. Make required
fine adjustments to record zertl and 10k pot for full
scale chart deflection. The recorder is now calibrated
for 360' or 0.2f.Lsec full scale.
3-17. Frequency Difference Measurement: To perform
the frequency difference measurement, proceed as
follows:
a. Connect equipment shown in Figure 3-6.
b. Set HP 8405A Vector Voltmeter PHASE
RANGE to 180' and METER OFFSET switch to 0.
c. Determine frequency error Llflf using the relation-
ship Cit
~ill
t !
d. Since chart calibration is 0.2 .usee full range (at
5 MHz), error in proportional parts can be determined
from the strip chart record as illustrated in Figure 3-4.
Modei5065A
Circuit Diagrams, Theory, and Maintenance
Figure 3-4. Error Measurement
Example: Assume instrument under test has a
phase change (over a 7-hour measurement period)
of 0.1flsec (recorder half scale)
6t
~
1 x 10-'s = 3.96 x 10·" freq. diff.
t 7 hrs. 2.52
x
1 O's
e. Since one minor division of the MAGNETIC
FIELD adjustment changes the 5065A frequency by 4
parts in 1012, in Figure 3-4, the dial would be changed one
minor division. During the phase measurement a cw
movement of the HP 8405A phase meter indicates the
5065A frequency is higher than the reference standard
and a ccw movement indicates the frequency is !ower
than the reference. If the MAGNETIC FIELD adjustment
is at the end of the range:
1. Set the Magnetic Field adjustment to 5.00 and
measure the frequency offset again. This is the
"desired change in offset" Item 2 in Table 3-4.
See Table 3-6 for an example of this calculation.
-·
f.
Increasing the MAGNETIC FIELD setting
increases the 5065A frequency and decreasing
this setting lowers 1t. Make this adjustment as re-
quired to aiign the 5065A with the reference
standard.
g. After the MAGNETIC FIELD control has been
reset, another phase comparison will show lf the adjust-
ment is correct, or if another adjustment is needed.
3-18. FREQUENCY COMPARISON USING K34-59991A
LINEAR PHASE DETECTOR
a. Connect the K34-59991A OUTPUT terminals to
a HP 680 Strip Chart Recorder or equivalent. Set recorder
for 1V full scale and 1 in./hr. and turn on recorder.
b. Connect K34-59991A to line power and turn on
the power switch.
3-5