ESI VideoBridge 2150, Service Manual

Page: 126 / 332

Ta i l o f f T i me
i s t h e f i xe d p o r t i on o f me a s u re me n t t i me w h i c h i s s e t a t
app r o x i ma t e l y 5 m s . D u r i n g ta i l o f f t i me t h e A / D c o n ve r t e r i s broug h t t o
z e r o , a nd t h e c oa r s e a n d f i ne c ou n t e rs a re a ccumu l a t i ng mea s u r e m e n t
d a t a . D u e t o va r i a t i on s c a u s e d by t h e s y n c h r o n i z a t i on o f i n t e r n a l
t i m i ng , t a i l o f f t i me c a n r a n g e f r om 4 ms t o 6 ms ( s e e S a mp l e T i me ) .
Samp l e T i me
i s I n te g ra t i on t i me + 4 m s o f Ta i l o f f t i me rounded t o t he
n e x t h i g he r e ve n numbe r . F o r e xampl e , 2 7 . 5 m s + 4 ms
=
3 1 . 5ms
--.
3 2 m s .
r--
T OTAL SAMPLE TIME
I NTEG ATI ON TIME
AND
F I N E
(TAI LOFF T IME)
I
COUNTS
I
I
I
I
I
I
I
I
I
I
I
I
I
1
=
I n te g ra t i on on me a su re d s i g na l .
2
=
I n t e g r a t i on on m i x t u re o f mea s u re d a n d re f e re n ce s i g na l .
coun t e r sums t h e s e pe r i od s .
C oa r s e
3
=
I n t e g ra t i on on re f e r e n c e s i gna l on l y .
w i t h p r e v i o u s pe r i o d s .
C oa r s e c o u n t e r s u m s t h i s
4
=
I n t eg r a t i on o n f i ne r e f e re n ce .
a d d i n g i t s c ou n t t o t h e c oa rse
1 0 2 4 f i ne coun t s ) .
F i ne c ou n t e r mon i t ors t h i s pe r i od
c o u n t e r t o ta l ( 1 c o a r s e c ou n t
=
F i gure 2-1 5 . Samp l e T i me
D e te c tor Reve rsa l
i s t h e s i newave d e t e c t o r r e v e rs i n g po l a r i t y a f te r
t he f o u r t h s a mp l e t i me . T h e s e cond s e r i e s o f mea s u re m e n t s a r e m a d e i n
t h e opp o s i t e p o l a r i ty .
a l g e bra i c a l ly a dd e d ( i . e .
T h e s e
( 1 - 5 )
two
( 2 -6 ) ,
s e r i e s o f
( 3 - 7 ) , ( 4 - 8 » ,
mea sureme n t s a re
t o c a n c e l o f f s e t
v o l t a g e s i n o p e r a t i o n a l a mp l i f i e r s a n d s y n c h r o n i z e d l i n e r e l a t e d
p i ckup . N e i t h e r l i ne l o c k t i me nor a dd i t i on a l s e t t l i ng t i me i s r e q u i re d
f o r t h i s m e a s u re me n t me t h o d .
2 - 8 8
e l s l i 2 1 5 0 / 2 1 6 0 5 / 8 5