Time Period M Easurement - Tektronix 5440 Instruction Manual

6 . M easure t
h
e
h
orizontal deflection in d ivisions and
determi
n e t h e p eriod by t
h
e following formula :
M o
d
ifie d
h
orizo
n
tal
Period = Deflectio
n Χ deflection
F actor ( d ivisions)
E
XA
MPLE :
Assume α references ignal fre
qu e
n
cy of 455
h
ertz (period 2 .2 millisecon
d s), α Sec/Div switc
h
setting of
.2 ms, and α
h
orizontal deflection of eig
h
t divisions .
Substituti
n
g t
h
ese values in t
h
e Deflectio
n
Co
n
version
F
actor formula (step 2) :
2 .2 ms
= 1 .375
(8) (0 .2 ms)
T
h
e
n
, wit
h α Sec/Div switc
h
setting of 50 μ s, t
h
e
M
odified Deflectio
n F
actor (step 5) is :
(50 μ s) (1 .375) = 68 .75 microseconds/divisio
n
To d etermine t h e time period of an a
p
plie d signal w
h
ic
h
com
p
letes o
n
e cycle in seve
n h
orizontal
d
ivisions, uset
h
e
P
eriod formula (ste p 6) :
(68 .75 μs) (7) = 481 microsecon
d
s
T
h
is p roduct can be converte d to fre
qu
e
n
cy by ta
k
i
n
g
t
h
e reciprocal of t
h
e p eriod (see a
p
plication of Deter-
mi
n
i
n
g
F
re
q
uency) .
Time
P
erio
d M
easurement
1 . Co
nn
ect t
h
e sig
n
al to t
h
e vertical i
n
put con
n
ector,
select eit
h
er ac or d o i
np
ut cou
p
li
n g, an d set t
h
e
V
olts/Div
switc
h
to d isplay about four divisio
n
s of t
h
e waveform .
2 . Set t
h
e time-base triggering controls to obtain α
stable dis
p
lay . Set t
h
e Sec/Div switc
h
to t
h
e fastest swee p
rate t
h at will permit
d
is
p
laying one cycle of t
h
e waveform
in less t
h
a
n
eig
h
t divisions (some non-linearity may occur
in t
h
e first a
n
d last graticule divisio
n
s of
d
is p lay) . R efer to
F ig . 1-8 .
3 . Ad
j
ust t
h
e vertical P ositio
n
co
n
trol to move t
h
e
p
oi
n
ts between w
h
ic
h th
e time measureme
n
t is ma d e to
t
h
e ce
n
ter
h
orizo
n
tal li
n
e . A
dj
ust t
h
e
h
orizontal
P
osition
control to center t
h
e time-meas
u rement poi
n
ts wit
h
i
n
t
h
e
ce
n
ter eig
h
t divisions of t
h
e graticule .
O
perating Informatio
n
-5440
4 . M easure t
h
e
h
orizo
n
tal d istance betwee
n
t
h
e time
measurement points . B e sure t
h
e variable Sec/Div co
n
trol
is in t
h e Cal p osition .
5 . M ulti p ly t
h
e d ista
n ce measured in step 4 by t
h
e
setti
n
g of t
h e Sec/Div switc
h
.
E
XA
MPLE :
Assume t
h
at t
h
e h
orizontal distance
between t
h e time-measurement p oints is five d ivisions a
n
d
t
h e Sec/Div switc
h
is set to .1 ms . U sing t
h
e form
u
la :
h
orizontal Sec/Div
P
eriod = d ista
n
ce
Χ switc
h
= (5) (0 .1 ms) = 0 .5 ms
(divisions) setting
T
h
e
p
erio d is 0 .5 millisecond .
Determini
n
g
F
re q uency
Th e time measurement tec
hn
i
q
ue ca
n
also be used to
determi
n
e t
h
e frequency of α signal . T
h
e fre q ue
n
cy of α
p
eriodically recurrent signal is t
h e reci p rocal of t
h
e time
duration ( p erio d ) of o
n
e cycle . U se t
h
e following
proce
d
ure :
1 . M easure t
h
e
p
erio
d
of o
n e cycle of t
h
e waveform as
described in t
h
e previous applicatio
n
.
2 . Ta
k
e t
h e reciprocal of t
h
e period to d etermine t
h
e
fre q ue
n
cy .
E
XA
MPLE :
T
h
e frequency of t
h
e sig
n
al s
h
ow
n
i
n F
ig . 1-
8, w
h
ic
h h as α period of 0 .5 milliseco
n
d is :
To measure t
h
e time (perio
d
) betwee
n two points on α F requency =
period 0 .51ms
= 2 kilo
h
ertz
waveform, use t
h e following p rocedure :
ι
j H
o
r
izo
n
tal
distance
F
ig . 1-8 .
M
easu
r
i
n
g time
du
ratio
n
(
p
eriod) b etwee
n p
oi
n
ts on α
waveform .
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