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M od e l 5363 6
Service
8-68. In s h o rt , a si m p l if i e d way of t h i n k i n g of t h e c a l i b ra t i o n process i s t h a t t h e state mac h i n e
A 1 U 1 1 . 25 , 2 8 , 30 · t u rn s o n t h e a p p roperi ate probe, resets t h e R eference D A C A 2 s o t h a t it's
o u t p u t level is O .OOV . o u tp uts -7 5 mV v i a the STA RT Cal i b ra t i o n D A C A 1 U 3 , U 4 to t h e probe,
c h ecks for a STA R T T R I G G E R . i n c re m e nts t h e D A C output b y -r0 .6 mV, c h ec k s for a t r i g g e r,
etc. T h i s process i s re peated u n t i l a START T R I G G E R i s rece i ved , or a ti m e r A 1 U 1 4A o n t h e
m o th e rboa rd w h i c h was t r i g g e red e a r l y i n t h e Cal i b ra t i o n R o u t i n e , state 1 70 s i g n a l s t h a t t h e
c a l i b ra t i o n p rocess h a s t a k e n too l o n g . T h e t i m e rs o ut p u t i s >220 m s l o n g , a n d i s u s e d t o te l l
t h e state m a c h i ne t h a t s o m et h i ng i s n o t a l l o w i n g t h e probe s t o c a l i b rate.
8-6 9 . O nce the process has bee n c o m pl eted for the STA R T c h a n ne l probe, t h e state mac h i n e
l ocates a n d e n a b le s t h e S T O P p ro b e a n d c a l i b rates i t i n t h e s a m e way. T h e S T O P c h a n n e l
Ca l i b ra t i o n D A C c o n s i sts of A 1 U 1 / U 6 w h i l e t h e a ssociated c o m p o n e nts a re J F ETs A6/A7 U 2 ,
a n d transistor a rrays A 1 U 1 3/ 1 7 . T h e c a l i b ra t i o n ro u t i n e i s e x a c t l y t h e s a m e u s i n g t h e STO P
c h an ne l c o m po n e n t s .
8-7 0 . I f t h e c a l i b ra t i o n process i s n o t c o m pl eted beca use o f the state mac h i ne n o t rec e i v i n g a
t ri g g e r f o r s o m e rea so n , i n e i t h e r t h e STA R T or STOP c h a n ne l s , t h e state m a c h i n e w i l l e x i t t h e
Ca l i b ra t i o n R o u t i n e a n d g o to t h e E r r o r R o u t i n e . T h i s ca uses t h e state mac h i ne to l o o p a n d
b l i n k t h e L E D s o n a n d off .
8-7 1 . T h e J F ET pa i rs of U 1 a n d U 2 i n the probe a sse m b l i e s a re matched o r sorted at t h e
m a n ufac t u re r p e r H P spec if i c a t i o n s . T h i s a ss u res a c l oseness i n spec ificati o n s between a l l o f
t h e STA R T a n d S T O P i n p ut ' i nv e rt i n g J F E T s .
8-7 2 . H owever, t h e re i s sti l l a d i fference i n t h e V g s , rati n g s of t h e two J F ETs w i th i n a s i n g le
A6/A7 U 1 o r U 2 p a c k a g e . T h i s m e a n s that t h e t r i g g e r voltage of the i nve rti ng J F ET a n d that of
t h e n on i nv e rt i n g J F ET w i l l be off by w h ateve r t h e d iffe rence i s between t h e i r re spect i ve V g s
rat i n g s . A l s o , a s m a l l offset e xits between t h e p l u s a n d m i n u s t e rm i n a l s o f t h e c o m p a rators
w h i c h se n se a t r i g g e r s i t uati o n . And f i n a l l y , the c o m m o n -base l oa d of t h e c u rrent so u rce of
Q 1 /C R 1 or Q 2/ C R 2 adds to t h i s v o l ta g e d i sc re p e n c y .
8-73. T h e s u m o f a l l o f these v o l t a g e d iffe re nces i s termed t h e tota l offset v o l ta g e . If a l l o t h e r
e r rors i n t h e t r i g g e ri n g syste m we re z e r o , t h i s v o l ta g e wo u l d be e xa c t l y t h e d iffe re nce between
t h e v o l ta g e rea d i ng f ro m the t h u m b w h e e l s w i t c h e s and voltage at w h i c h t h e i ns t r u m e n t probe
tri g g e rs . S i nce this tota l offset voltage h e reafte r refe rred to a s s i m pl y t h e offset voltage c a n
b e r e l a t i v e l y h i g h w h e n c o m pa red to t h e i n p u t v o l ta g e , i t m u st some h ow be ca l i b rated o u t of
th e c i rc u i t .
8-74. T h e fol l ow i n g ,
Fig ure 8-4 ,
i s a s i m pl if i ed d ia g ra m of t h e i n p u t c i rc ui t of t h e 5363 6. I t i s
basica l l y a d iffe re n ti a l a m p l i f i e r of l o w c o m m o n -m o d e g a i n , w h i c h pe rm i ts o p e ra t i o n ove r a
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1 OV ra n g e .
8-7 5 . To ze ro o u t t h e effect o f t h e offset v o l ta g e , t w o Ca l i b ra t i o n D A Cs a re u s e d w h i c h f i n d
a n d store t h e offset va l ue se l e c ted STA R T a n d S T O P p r o b e s o n e D A C f o r eac h . T h i s process
g ets t h e t r i g g e r e rror d ue to offset voltage d o w n f ro m a s m u c h a s 75 mV to .6 mV.
8-7 6 . T h e i m portance of t h e c a l i b ra t i o n c i rc u i t c a n n o w be see n . I t effe c t i ve l y red uces the
tri gg e r e rror d ue to off set voltage to a neg l ig i b l e l e ve l , prod u c i n g a m o re acc u rate
m e a s u re m e n t .
' T h e Refere n ce D A C A2 I S te m p o ra ri l y reset d u r i n g t h e C a l i b rat i o n R o u t i n e State 1 66 . w h i c h p u t s I t S
o u t p u t v o l t a g e at 0 OOV T h e refore t h e o ut p u t of t he Refe re n c e D A C at p i n 6 of A 2 U 9 i s t h e o u t p u t of t h e
C a l i b rat i o n D A C d u ri n g t h e c a l i b ra t i o n c y c l e
8-1 7
Summary of Contents for 5363B
Page 52: ......
Page 116: ...Figure 8 9 MAIN PROGRAM I DLE LOOP ROUTI NE FLOWCHART Sheet 1 of 5 See Page 8 39 ...
Page 118: ...Figure 8 9 MAIN PROG RAM I DLE LOOP ROUTI N E FLOWCHART Sheet 2 of 5 See Page 8 41 ...
Page 120: ...Figure 8 9 MAIN PROG RAM I DLE LOOP R O U T I N E FLOWC HART Sheet 3 of 5 See Page 8 43 ...
Page 122: ...Figure 8 9 MAIN PROG RAM I DLE LOOP ROUTIN E FLOWCHART Sheet 4 of 5 See Page 8 45 ...
Page 126: ...Figure 8 1 0 HP IB PROGRAM HAN DSHAKE R OUTI N E FLOWCHART Sheet 1 of 4 See Page 8 49 ...
Page 128: ...Figure 8 1 0 HP IB PROG RAM HAN DSHAKE ROUTINE FLOWCHART Sh eet 2 of 4 See Page 8 5 1 ...
Page 130: ...Figure 8 1 0 HP I B P R O G RAM HAN DSHAKE ROUTI N E FLOWCHART Sheet 3 of 4 See Page 8 53 ...
Page 132: ...I I G6 r ciJ I I I I i I I I loY 8 I _ x __ c I I j ...
Page 134: ... 1 J 0 0 3 RI I H I H tt t tTd ci ...
Page 137: ... W2 Figure 8 1 1 A 1 Motherboard Schematic Diagram Sheet 2 of 2 ...
Page 138: ......
Page 139: ... Model 53638 ServIC8 Figure 8 1 1 AI uclherboard Schematic Sheet if 2 8 59 ...
Page 142: ... Pl Figure 8 1 2 A2 Digital la Analog Converter Assembly ...
Page 145: ... 3 A3 Calibrate Assembly Figure 8 1 ...
Page 150: ... 1 F 6 O 3000 2V I V 1000 Ilk L j 0104 t r r 1 3 I _ _ HH t t1 14 t PIO 4fOO PI roc r I NC ...
Page 154: ... TI P BODY TIP P R O B E Figure 8 1 6 A 6 A 7 Probe A ssembly m ...