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3 . 3
Temperature Readout
The s e n s o r and h e a t e r s h o u l d b e i n s t a l l e d f o l l o w i n g t h e s u g g e s t i o n s
l i s t e d i n t h e " I n s t a l l a t i o n and A p p l i c a t i o n Notes f o r Cryogenic Sensors"
b r o c h u r e i n S e c t i o n
VIII.
Connect t h e s e n s o r t o t h e i n s t r u m e n t f o l l o w i n g t h e diagram i n F i g u r e
2.1.
Turn t h e power s w i t c h t o ON and o b s e r v e t h a t t h e d i s p l a y shows t h e
p r o p e r temper a t u r e r e l a t i v e t o t h e s amp 1 e temper a t u r e.
If
t h e d i o d e o r l e a d w i r e s a r e s h o r t e d , t h e d i s p l a y w i l l r e a d one o f
t h e f o l l o w i n g :
Curve
PROM U13
D i s p l a y
0
B3
431.0
A
B 4
433.7
B
B6
428.0
If
t h e d i s p l a y r e a d s one of t h e above and b l i n k s , t h e d i o d e i s con-
n e c t e d backwards.
In
t h e c a s e of a n open l e a d , t h e d i s p l a y w i l l s l o w l y d r i f t
h i g h e r i n t e m p e r a t u r e from t h e l a s t v o l t a g e r e a d i n g t a k e n by t h e A/D c o n v e r t e r .
The s e n s o r and r e a d o u t d i s p l a y s h o u l d f o l l o w T a b l e 3 . 3 which i l l u s t r a t e s
t y p i c a l v a l u e s e x p e c t e d of t h e s t a n d a r d DT-500-DRC
o r DT-500CU-DRC-36
s e n s o r s
f o r your a p p r o p r i a t e c u r v e .
I f t h e i n s t r u m e n t o r s e n s o r does n o t a g r e e w i t h v a l u e s l i s t e d i n t h e
t a b l e , w i t h i n t h e a c c u r a c y of t h e system, c o n s u l t s e c t i o n s on i n s t a l l a t i o n
a n d / o r s e c t i o n on t r o u b l e s h o o t i n g t o d e t e r m i n e t h e c a u s e and c u r e of t h e
m a l f u n c t i o n .
3 . 3 . 1
Remote P a r a l l e l BCD I n p u t / O u t p u t Option
The BCD o p t i o n c o n s i s t s of a
1 6
b i t p a r a l l e l o u t p u t of t e m p e r a t u r e
a n d , f o r t h e DRC-7C/70C c o n t r o l l e r s , a
1 4
b i t p a r a l l e l i n p u t of s e t p o i n t i n
k e l v i n d e g r e e s .
The BCD i n and o u t i s h a n d l e d through c o n n e c t o r 5 3 , a 40 p i n
3 M c o n n e c t o r on t h e rear p a n e l of t h e i n s t r u m e n t (Key 7 of F i g u r e 3 . 2 o r Key
1 7
of F i g u r e 3 . 4 ) .
A jumper w i r e i s p l a c e d on t h e p r i n t e d c i r c u i t board below
I.C.'s
U10 and
U11
and above c a p a c i t o r C21 ( s e e F i g u r e
6 . 4
-
DRC-7/70 S e r i e s
Components Layout).
C u t t i n g of t h i s jumper a l l o w s t h e u s e r t o e n a b l e a remote
s e t p o i n t by s e t t i n g Pin-38,
J1 h i g h ( s e e T a b l e 3 . 2 ) .
Decade c o u n t e r s i n t e r n a l
t o t h e i n s t r u m e n t p r o v i d e a 1-2-4-8
code u s i n g p o s i t i v e l o g i c w i t h s t a n d a r d
TTL l e v e l s of
0.4
v o l t s f o r t h e l o w ( o r 0) s t a t e and 2.4 v o l t s f o r t h e h i g h
( o r
1)
s t a t e under f u l l l o a d c o n d i t i o n s .
two s t a n d a r d l o a d s , 3 . 2
mA,
i n t h e l o w s t a t e .
The d r i v e r s a r e s u f f i c i e n t t o s i n k
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