Tektronix 434, Instruction Manual

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Operating Instructions—434
S IN G LE SWEEP. When the signal to be displayed is n o t
repetitive or varies in am plitude, shape, or tim e , a conven­
tio n a l re p e titive display may produce an unstable presenta­
tio n . T o avoid this, use the single-sweep feature o f the 434.
The S IN G LE SWEEP mode can also be used to photograph
a n on-repetitive signal.
T o use the S IN G L E SWEEP mode, firs t make sure the
trigger c irc u it w ill respond to the event to be displayed. Set
the Sweep MODE sw itch to A U T O or NORM and obtain
the best possible display in the norm al manner (fo r random
signals, set the trigger c irc u it to trigger on a signal w hich is
a p p ro x im a te ly the same am p litu d e and frequency as the
random signal). Then, set the Sweep MODE to S IN G LE
SWEEP and press the RESET b u tto n . When the RESET
b u tto n is pushed, the n e xt trigger pulse initiates the sweep
and a single trace w ill be presented on the screen. A fte r this
sweep is com plete, the Sweep Generator is "lo c k e d o u t"
u n til reset. The R E A D Y lig h t is illu m in a te d when the
Sweep Generator has been reset and is ready to produce a
sweep. T o prepare the c irc u it fo r another single-sweep
display, press the RESET b u tto n again.
H orizontal Sweep Rates
The T IM E /D IV switch provides 23 calibrated unm ag­
n ifie d sweep rates ranging fro m 0.2 m icrosecond to 5
seconds/division. The three fastest indicated sweep rates
can be achieved o n ly by using sweep m agnification. The
V A R c o n tro l provides c o n tin u o u sly variable sweep rates
between the settings o f the T IM E /D IV sw itch . The accu­
racy specifications fo r the calibrated sweep rates apply over
the fu ll ten h o rizo n ta l divisions o f d e fle ctio n .
Sweep M agnification
The sweep m agnifier expands the sweep up to a m a x i­
m um o f 50 tim es. The center p art o f the unm agnified
display is the p o rtio n visible on the screen in m agnified
fo rm . E quivalent length o f the m agnified sweep is ten
divisions m u ltip lie d by the am o u n t o f m ag n ifica tio n (500
divisions at 50 tim es m a g n ific a tio n ); any 10-division p o r­
tio n can be viewed by adjusting the h o rizo n ta l POSITION
c o n tro l to bring the desired p o rtio n o n to the viewing area.
The dual-range feature o f the h o rizo n ta l PO SITIO N c o n tro l
(see H o rizo n ta l P osition C o n tro l discussion w h ich fo llo w s)
is p a rtic u la rly useful w hen the m agnifier is on.
T o use the m agnified sweep, firs t p o sitio n the p o rtio n o f
the unm agnified display to be expanded to the center o f
the graticule. Push in on the T IM E /D IV kn o b and tu rn
clockwise u n til the desired am o u n t o f m ag n ifica tio n is
achieved (up to a m axim um o f 50 tim es). The equivalent
tim e /d iv is io n is indicated d ire c tly by the T IM E /D IV knob,
and is a calibrated sweep rate when the V A R c o n tro l is in
its calibrated d etent.
H orizontal Position C ontrol
The dual-range h o riz o n ta l POSITION c o n tro l used in the
434 provides a c o m b in a tio n o f coarse and fin e adjustm ents
in a single c o n tro l. When this co n tro l is ro ta te d , fine
p o s itio n in g is provided fo r a range o f about 0.3 division fo r
norm al sweep, or a bout 15 divisions fo r m agnified opera­
tio n and the trace can be positioned precisely. Then, after
the fin e range is exceeded, the coarse adjustm ent comes
in to e ffe c t to provide rapid po sitio nin g o f the trace. T o use
this c o n tro l e ffe c tiv e ly fo r precise p o sitio nin g , firs t tu rn the
c o n tro l to move the trace slig h tly beyond the desired
po sitio n (coarse range). Then reverse the d ire c tio n o f ro ta ­
tio n to use the fin e range to establish the precise trace
p o sitio n desired.
External H orizontal In p u t
In some applications it is desirable to display one signal
versus another signal rather than against tim e (internal
sweep). The E XT H O R IZ p o sitio n o f the T IM E /D IV sw itch
provides a means fo r applying an external signal to the
h o rizo n ta l a m p lifie r fo r th is ty p e o f display.
C onnect the external h o rizo n ta l signal to the EXT
H O R IZ con n e cto r. The d e fle c tio n fa c to r is a b o u t 0.5 v o lt/
d ivisio n . The X and Y channels o f this in s tru m e n t are n o t
tim e matched and some in h e re n t phase s h ift is apparent.
Take this in h e re n t phase s h ift in to account w hen m aking
measurements. For aid in in te rp re tin g lissajous displays,
refer to the reference books listed under A p p lica tio n s.
Inte n sity M odulation
In te n s ity (Z-axis) m o d u la tio n can be used to relate a
th ird item o f electrical phenomena to the vertical (Y-axis)
and the h o rizo n ta l (X-axis) coordinates w ith o u t changing
the wave shape. A Z-axis m o d u la tin g signal applied to the
C RT c irc u it changes the in te n s ity o f the displayed wave­
fo rm to provide this display. "G ra y scale" in te n s ity m odu­
la tio n can be obtained by applying signals w hich do n o t
co m p le te ly blank the display. Large a m plitude signals o f
the co rre ct p o la rity w ill co m p le te ly blank the d isplay; the
sharpest display is provided by signals w ith a fast rise and
fa ll. The voltage am p litu d e required fo r visible trace m o d u ­
la tio n depends on the setting o f the IN T E N S IT Y c o n tro l.
A t norm al in te n sity level, a fiv e -v o lt peak-to-peak signal
produces a visible change in brightness.
T im e markers applied to the Z A X IS in p u t connector
provide a d ire c t tim e reference on the display. W ith u n ca li­
brated h o riz o n ta l sweep o r X -Y mode o peration, the tim e
markers provide a means o f reading tim e d ire c tly fro m the
display. However, if the markers are n o t tim e-related to the
displayed w aveform , a single-sweep display should be used
(fo r internal sweep o n ly) to provide a stable display.
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