Tektronix 7000 Series Manual page 16

interval, wh ic h ca n be selecte
d
on the
7D14, the burst to
b
e measure
d
must
b
e wi
d
er than 1 ms . The resol ution of
*h e 7D14 using th e 1 ms interval is 1
kH z.
M
easurement resolution is thus
limite
d
on lower freq uency signals.
F
or this burst fre
q
ue n cy measurement,
the 1 ms MEAS U REMEN T I NTERVAL is
selecte
d
. The I NPUT S EN SITI VITY is
set to 100 mV and the TRIGGER LEVEL/
SLOPE control is set to count on th e
positive-going slo
p
e of each cycle with-
in t he burst. F
ig . 14 shows α bu rst fre-
quency measurement of 3.577 MH z. On
bu rsts of 10 ms or greater, the 10-ms
ME AS UREMENT I NTERVAL ca n be se-
lecte
d to increase the resolution
b
y α
factor of te n .
counting the number of cycles
or events in α burst
7Α26
Dis p lay
M o d e . . . . . . . . . . . . . . . . . . . . . . . C h o p
Co up ling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . DC
Se n sitivity
C h 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . as
r
e q .
C h 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 V
Trigge r So urce . . . . . . . . . . . . . . . . . . . . . . . C h 1
Burst
Signal
7Α 26 7Α 19 7D14 7 Β 92 Α
CH 1
σ
CH A
7704Α
Delaye
d
Swee
p
Gate
Out Rear
P
anel
7D14 7 Β92Α
Manual Gate . . . . . . . . . . . . . . . . . . . . . . . . . . Off
M
o de . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A u to
Display Ti me . . . . . . . . . . . . . . . . . . . .
M
i drange Co up li ng . . . . . . . . . . . . . . . . . . . . . . . . . . . . . AC
Fig. 15 SNOWS the equipment
Set- U for
Cou p li n g . . . . . . . . . . . . . . . . . . . . . . . . . . . . . DC So u rce
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ιη t.
ρ Βω . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
525 MHz
τime/ οι y . . . . . . . . . . . . . . . . . . . . . . . . Dι y
Time
Counting
t
he n u mber of Cycles i n α
Ι
L
evel/Slo pe . . . . . . . . . . . . . . . . . . . . . . . . . V ar. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ru ns afte r d ly
Input Sensitivity . . . . . . . . . . . . . . . . . . . 100 MV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Alt . Off .
bu rst. In t h is case, the
d
elaye
d
swee
p
gate sets th e measurement interval of F
ig . 15 .
E
q
uipment setu p for cou nting the number of cycles in α burst.
t
h e 7D14 . Si n ce t h e d
elaye
d
swee
p
gate
is not α
p
recision cali brated measure-
ment interval, οηΙγ t he actual count is
is
d
is
p
laye
d
in the u
pp
er center of the α meas u reme n t
f O 3114 cycles in α
" rea
d
o ut wit h no frequency units. Once
crt. The ±1 co unt ambiguity inh erent burst. Th e only limitation in ma king t his
α stable d
is
p
lay is obtained, the Delay in cou n ter measurements
d
oes not af- measurement is th at th e minim u m in
p
ut
Time
M
ultiplier an
d
t
he
V
ariable Time/ fect the accuracy of this meas u rement cycle wi dth to th e CH Α
I
NPU T is 10 ns,
Division controls are set to obtain α d
e- if the co unter gate is o
p
ene
d
and close
d
an
d
t
h e gate in
p ut must be at least 500
laye
d
swee p gate that encloses the
between bursts as shown . Fig . 17 s h ows
ns wi
d
e.
burst to be measure
d
. (N ote that this is
the o
pp
osite of t h e frequ ency measure-
ment .) Si n ce th e d
elaye
d
swee
p
gate is
d
is
p
laye
d
on the CRT along with
t
he
Bu rst, the
p
osition and wi
d
th of th e
measurement interval can be set q
uick-
ly an
d
accurately .
Wh en o
p
erating the 7D14 in α vertical
plug-in com
p
artment of t he oscillo-
sco
p
e, th e out
p
ut of t he counter s h a
p
er
can also be d
is
p
laye
d
(see
F
ig . 16) .
Simu ltaneo u s viewi n g of the 7D14 trig-
ger sha
p
er out
p
ut with
t
he burst ma kes
it
p
ossible to a
d
j ust the 7D14 TRIGGER
LEVEL control to count only those cy-
cles of the
d
esire
d
am
p
litude as show n.
The mainframe vertical mo
d
e switch
must be set to alternate or c h o
p
to view
F
ig . 16 . Display of counter shaper
F
ig . 17. Display of 3114 cycle burst .
t
he trigger sh a
p
er o u t
p
ut . As the TRIG-
output.
G ER LEVEL control is a
d
j usted for
h
ig her levels, th e lower am
p
lit ude cy-
cles of the bu rst are n
ot recognize
d
~by
t
h e 7D14 trigger circuit. The count