Tektronix 434, Инструкция по эксплуатации

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O p erating In s tru c tio n s —4 3 4
9. Measure the distance in divisio n s betw een th e re fe r­
ence line and th e p o in t on the w a ve fo rm at w h ic h the DC
level is to be measured. F o r exam ple, in Fig. 2-8 the
m easurem ent is made betw een th e reference line and p o in t
A .
10. Establish th e p o la rity o f the signal. I f the w a ve fo rm
is above the reference line the voltage is p o s itiv e ; b e lo w the
lin e , negative (w ith th e IN V E R T sw itch in fo r Channel 2).
11. M u ltip ly th e distance measured in step 9 b y the
V O L T S /D IV sw itch se ttin g . In clude th e a tte n u a tio n fa c to r
o f th e p ro b e , if using a p ro b e th a t does n o t have a scale
fa c to r sw itc h in g c o n n e c to r.
E X A M P L E . Assume th a t th e ve rtic a l distance measured
is 4.6 d ivisio n s (see Fig. 2-8) and the w a ve fo rm is above the
reference lin e w ith a V O L T S /D IV s w itch setting o f 2 V.
C om parison Measurements
In some a p p lic a tio n s i t m ay be desirable to establish
a rb itra ry u n its o f m easurem ent o th e r th a n those in d ica ted
b y th e V O L T S /D IV sw itch o r T IM E /D IV s w itc h . T h is is
p a rtic u la rly useful w hen com p a rin g u n k n o w n signals to a
reference a m p litu d e o r re p e titio n rate. One use fo r th e
com parison-m easurem ent te ch n iq u e is to fa c ilita te c a lib ra ­
tio n o f e q u ip m e n t (e.g., on an assem bly-line test) w here the
desired a m p litu d e or re p e titio n rate does n o t produce an
e xa ct n u m b e r o f d ivisio n s o f d e fle c tio n . T h e a d ju s tm e n t
w ill be easier and m ore accurate if a rb itra ry u n its o f
m easurem ent are established so th a t c o rre c t a d ju s tm e n t is
in d ic a te d b y an exact n u m b e r o f d ivisio n s o f d e fle c tio n .
A rb itra r y sweep rates can be useful fo r com p a rin g h a rm o n ic
signals to a fu n d a m e n ta l fre q u e n c y , o r fo r co m p a rin g the
re p e titio n rate o f th e in p u t and o u tp u t pulses in a d ig ita l
c o u n t d o w n c irc u it. The fo llo w in g p ro ce d u re describes h o w
to establish a rb itra ry u n its o f measure fo r com parison
measurements. A lth o u g h the p rocedure fo r establishing
v e rtica l and h o riz o n ta l a rb itra ry u n its o f m easurem ent is
m uch th e same, b o th processes are described in d e ta il.
Using the fo rm u la :
instantaneous
V oltage
v e rtica l
distance X p o la rity X
(divisions)
V O L T S /D IV
se ttin g
S u b s titu tin g the given values:
Instantaneous
V oltage
4 .6 X +1 X 2 V
T he instantaneous voltage is +9.2 volts.
F ig . 2 -8 . M e a s u rin g in s ta n ta n e o u s D C v o lta g e w it h re s p e c t t o a r e fe r­
ence v o lta g e .
V e rtic a l D e fle c tio n F a c to r. T o establish an a rb itra ry
ve rtic a l d e fle c tio n fa c to r based u pon a sp e cific reference
a m p litu d e , proceed as fo llo w s :
1. C o n n e c t th e re fe re n c e signal to the IN P U T
c o n n e c to r. Set th e T IM E /D IV sw itch to d isp la y several
cycles o f th e signal.
2 . S e t th e V O L T S /D IV sw itch and the V ariable
V O L T S /D IV c o n tro l to produce a d isp la y an e xa ct num ber
o f g ra tic u le d ivisio n s in a m p litu d e . D o n o t change the
V a ria b le V O L T S /D IV c o n tro l a fte r o b ta in in g the desired
d e fle c tio n . T h is d is p la y can be used as a reference fo r
a m p litu d e co m p a riso n measurements.
3. T o establish an a rb itra ry ve rtic a l d e fle c tio n fa c to r so
th e a m p litu d e o f an u n k n o w n signal can be measured
a ccu ra te ly a t any se ttin g o f the V O L T S /D IV s w itc h , the
a m p litu d e o f the reference signal m u s t be k n o w n . I f it is
n o t k n o w n , i t can be measured before the V a ria b le V O L T S /
D IV c o n tro l is set in step 2.
4 . D ivide th e a m p litu d e o f the reference signal (volts)
b y th e p ro d u c t o f the ve rtica l d e fle c tio n established in step
2 (divisions) and the se ttin g o f the V O L T S /D IV sw itch .
T h is is th e v e rtic a l conversion fa c to r.
V e rtic a l reference signal
C onversion = ____________ a m p litu d e (vo lts)_________
F a c to r ve rtica l d e fle c tio n V O L T S /D IV
(divisions) * sw itch setting
2-17