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Deta I L Ed T H Eory Of C A L I B Ra T I O N F U N C T I O N; Leve L C A L I B Ra T I O - HP 5363B Operating And Service Manual

Time interval probes
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M o d e l 5363 B
S e r v i c e
8 -6 0 .
T h e A a n d B p r o b e s a re i d e n t i ca l i n c i rc u i t ry. T h e a ssi g n m e n t of S TA R T a n d STOP
c h a n n e l s to the probes is d e te r m i n e d b y the user v i a t h e t h u m b w h e e l s w i t c h e s o r H P- I B . A
S i n g l e p r o b e c a n be a ss i g n e d a s S TA R T c h a n n e l , STO P c h a n n e l , o r b o t h . T h e prec i se t r i g g e r
poi n ts f o r b o t h S T O P a n d STA R T c a n b e d e f i ned b y d i a l i n g t h e d e s i red p ro b e , p o l a rity, t r i g g e r
l e ve l , a n d sl o p e s e l e c t i o n s i n to t h e t h u m b w h e e l a sse m b l y . T h i s d a ta i s c o n t i n u a l l y sca n n ed
and u p d ated b y t h e State M ac h i n e . The State M a c h i n e c o n t r o l s the i n p u ts to t h e c o m p a ra t o r s ,
s e t s t h e D A C to f u r n i s h refe re n c e v o l t a g e s f o r t h e p r o b e s , a n d o pe rate t h e t ri g g e r l i g h t s .
8 -6 1 .
T h e STA R T a n d S T O P c h a n n e l refe re n c e v o l t a g e s a re prod u c e d o n t h e D-to-A
c o n ve rt e r a sse m b l y A2 . A d i g i t a l B C D s i g n a l f ro m t h e t h u m b w h e e l s w i tc h e s or t h e H P- I B
I n te rface i s c o n v e rted t o a n a n a l o g refe re nce v o l ta g e b y t h e refe re n c e D A C A2 . Th i s i s
a l g e b ri c a l l y s u m med w i t h a s m a l l offset c o r re c t i o n v o l t a g e f ro m t h e m o t h e rboa rd ca l i b ra t i o n
D A C a n d stored b y i t s res p e c t i ve A n a l o g Latc h . T h i s ro u t i n e i s c o n t i n u o u s l y repeated , w i t h t h e
State M ac h i n e a l t e rn a t e l y s e l e c t i n g STA R T c h a n n e l o r S T O P c h a n n e l i n p u t d a t a . T h e
a l tern a t i n g ro u t i n e req u i res o n l y o n e refe re n c e DAC to p r o v i d e two d i s c rete d c v o l t a g e
refe re n c e s , w h o s e l e ve l s a re c o n t i n u o u s l y u p d a t e d , s a m p l e d , a n d sto re d . T h e se l e ve l s a re
ro u te d a s refe re nce v o l t a g e s to t h e p r o b e s , a n d o n rea r pa n e l B N C s .
8 -62.
D ETA I L E D T H E O R Y O F CA L I B R AT I O N F U N CT I O N S
8 -6 3 .
T h e 5363 B p e rf o r m s two s e l f -c o r rec t i n g f u n c t i o n s . T h e se two f u n c t i o n s a re L E V E L
Ca l i b ra t i o n a n d T I M E Z E R O C a l i b ra t i o n . Both a re c o n t ro l l e d b y t h e f ro n t p a n e l T I M E
Z E R O/ L EV E L t o g g l e s w i tc h .
8 -64.
Leve l Ca l i b ra t i o n
8 -6 5 .
R ef e r to s c h e m a t i c s i n b a c k sec t i o n of m a n ua l ,
T I M E Z E R O/ L E V E L s w i t c h i s p u s h ed to L EV E L , t h e ma c h i n e e x i ts f ro m t h e I d l e L o o p R o u t i n e
. p a rag ra p h 8 - 1 2 1 a n d g oe s to t h e Ca l i b ra t i o n R o u t i ne · p a ra g ra p h 8-1 2 3 . I n t h i s r o u t i n e t h e
state m a c h i n e c a uses t h e S TA R T c h a n n e l C a l i b ra t i o n D A C , A 1 U 3 , U 4 to o u t p u t a v o l t a g e of -
7 5 mV to t h e S TA R T c h a n n e l s of b o t h p r o b e s T h i s v o l t a g e c a n be t ra c e d f ro m t h e n o d e of
A 1 R 24 and A 1 R 8 to A 1 U 2
O F FS ET" to p i n 2 of A 2 U 9 o n t h e R efe re n ce D A C , A2 w h e re i t's s u m med w i t h t h e l e ve l
v a l u e * se l ec te d o n t h e f ro n t p a n e l l e vel s w i tc h es o r v i a H P- I B . T h i s v o l ta g e g o e s b a c k t o A 1 U 9
, i n p i n 8 , o u t p i n 7 a n d o n to t h e g a te p i n 2 o f t h e n o n i n ve rt of t h e n o n i ve rt i n g J F ET o f eac h
STA R T c h a n n e l A6/ A7 U 1
8 -6 6 .
T h i s - 7 5 mV offset vo l ta g e , a p p l i e d to t h e g a t e of t h e n o n i n ve rt i n g J F E T , i s i n c reased
one step a p p r o x i m a t e l y -r .6 mV at a ti m e u n t i l t h e i n p u t , or i n v e rt i n g , J F ET t u r n s on, s e n d i n g a
STA R T T R I G G E R o u t t h e w h i te l e a d to p i n 2 of A
p ro b e , A o r B , i s s e l e c ted a s t h e S TA R T p r o be . T h i s t r i g g e r s i g n a l i s a ct u a l l y a c u r re n t s i n k of
a p p r o x i m a t e l y 2 0 mA, s u p p l i ed by the - 1 5 V STA R T l i n e , a n d is not m a d e a va i l a b l e a sse rted
u n t i l the i n p u t J F ET ' c l o se s ' . T h e t r i g g e r s i g n a l p a sses on f ro m A 1 U24 or U 27 to A1 U 1 8 B a n d
A 1 U 1 9 B p i n 1 3 , to A 1 Q 1 3 , w h i c h p u t s a l o g i c " 1 " o n t h e STA R T T R I G . L l G H T l i n e . T h i s l i n e
r u n s b a c k to t h e Q u a l i f i e r S e l e c t o r M U X A
m ac h i n e l oo k i n g for a S TA R T T R I G G E R .
8 -6 7 .
S i nce a c o m m o n DAC i s u sed to c a l i b rate t h e STA R T c h a n n e l J F ETs of b o t h of the A
a n d B p r o b e s , t h e state m ac h i n e m u st s o m e h o w ' t u r n o n ' t h e a p p r o p r i ate p r o b e a n d t h e n sta rt
t h e ca l i b ra t i o n p rocess. T h i s i s d o n e b y a sse rt i n g
m ot h e r b o a r d A 1 u s i n g t h e C o m m a n d Latch A
p ro b e s e l e c t t h e A p ro b e a n d t u r n off t h a t of t h e B p r o b e . A l o g i C 0 on t h e S TA R T C H A N l i n e
d o e s j u st t h e o p p o s i t e . T h u s , w l t h o u t t h e - 1 5 V s o u rce t h e u n d e S i red p r o b e c a n n o t t r i g g e r a n d
c o nseq u e n t l y t h e t r i g g e r rec e i ved b y t h e state m a c h i n e h a s t o c o m e f ro m t h e s e l ected p r o b e .
8 - 1 6
in p i n 8 , out pin 7 to A 1 U 5 in pin 3 , out p i n 6 o r T P5 " D A C
o f t h e p r o b e s .
U 2 4 , o r p i n 6 of A 1 U27 , d e pe n d i n g o n w h i c h
1
U 2 1 w h i c h i s s t r o b e d , p e ri o d i c a l l y , b y t h e state
1
l o g i c 1
1
U 2 6 p i n 5 to t u rn o n t h e - 1 5 V s o u rce to t h e A
Fig ures 8 - 1 1
8 - 1 6 .
t h ro u g h
t h e S TA R T C H A N l i n e o n t h e
W h e n t h e

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