M Ulti-Trace Ph Ase Difference M Easu Reme Nt - Tektronix 5440 Instruction Manual

9 . Ad just the
h
orizontal Positio n co ntrol so the
Ch annel 1 (or left p lug-in) waveform (refere nce) crosses
t h e center horizontal line at α vertical graticule li ne .
10 .
M
easure the horizontal distance between the two
measurement
p oints (see F ig . 1-10) .
11 .
M
ulti
p
ly the measure
d
distance by the settin g of
the Sec/Div switc h.
EXA MPLE : Assume that the Sec/Div switc h is set to
50 μs a n
d
the
h orizontal distance between measurement
poi nts is four d ivisio n s .
U
sing the formula:
Sec/Div horizontal
Del
Time
ay
= switch Χ
distance
= (50 μs) (4) = 200 μ s
setting (
d
ivisions)
T he time d elay is 200 microseco nds .
C
ha nn el 1, or left
Chann el 2, or center
plug-in ( reference)
pl ug-in
tftfti
ti~ι+"~α~~
σσ~rι
F
ig . 1-10 . Measuri ng ti me difference between two pulses.
M
ulti-trace Ph ase Difference
M
easurement
Ph ase com p arison betwee n two or more signals of the
same frequency can be ma de usin g a dual-trace pl ug-i n or
two single-trace plug-ins . This metho
d
of phase difference
measurement can be used up to the freq ue ncy limit of the
vertical system . To ma ke th e com parison , use the follow-
ing
p
rocedu re :
1 . Set the in pu t cou
p
ling switches of t h e am
p
lifier
cha nn els to either ac or dc .
2. Set the Display switch on the time-base un it to either
Ch op or Alt. In ge n eral, C ho p is more suitable for low-
frequency signals and th e Alt position is more suitable for
h ig h-frequency sig nals .
M
ore information on
d
etermi n ing
th e mode is given un der
V
ertical Display
M
ode i n
t
h is
section.
O
p
erating Information-5440
3 . Set the vertical
p lug-in triggering switc h es to trigger
the
d isplay on Channel 1 (or left plug-i n ) and Ch annel 2 (or
center plug-i n ) .
4. Connect th e refere nce signal to the C han nel 1 in
p
ut
connector a n d comparison signal to the C hannel 2 (or
ce n ter p lug-in) input connector. The reference signal
sh ou ld
p recede thecom parison signal in time . Use coaxial
cables or
p
robes
wh ic h have similar time-delay
characteristics to connect the sig nals to the input co nn ec-
tors .
5. If the signals are of op p osite
p
olarity invert th e
C hannel 2 (or ce nter pl ug-in )
d
isplay . (Sig nals may be of
op posite
p
olarity
d
ue to 180° ph ase
d
ifference; if so, ta ke
th is into accou nt i n
t
he final calculatio n.)
6. Set th e
V
olts/Div switc h es and th e variable
V
olts/Div
co n trols so th e d
is
p
lays are eq ual a nd about five divisions
in amplitude .
7 . Set the time-base triggeri ng controls to obtai n α
stable
d
is play. Set the Sec/Div switch to α sweep rate
wh ic h d is p lays about one cycle of t h e waveform .
8 . M ove the waveforms to t he center of t h e graticule
with t h e vertical P ositio n controls .
9 . Turn the variable Sec/Div control until one cycle of
the refere nce signal (C han nel 1, or left
p
lug-in) occupies
exactly eig ht division s between the seco nd and tent h
vertical li nes of the graticule (see Fig . 1-11 ) . Eac h division
of th e graticule re
p
resents 45° of the cycle (360° - 8
divisions =45°/
d
ivisio n ) . T he swee
p
rate ca n be stated in
terms of degrees as 45°/divisio n.
C
ha nn el 1, or left
Ch annel 2, or center
pl ug-i n ( reference)
p l ug-in (laggi n g)
ι
t
ί
H
orizontal -r`-
dista nce ι
τ τ
ι ι
~_ 8 Divisions
ι
(360 o)
ι
F
ig . 1-11 . Measuri ng phase differe nce.
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