Az; Ovr; Ds1, Ds2, Laen; Pol - Philips PM2517E Service Manual

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Az,fr
lAuto zercl
T h e a u t o z e r o s i g n a l s a r e s w i t c h i n g t h e i n p u t v o l t a g e s t o t h e i n p u t s o f t h e A D C
( R e f e r t o 3 3 3 A D C a n d
3 . 3 . 4 . 2 . C o n t r o l L o g i c ) .
The AZ and AZ are determined by the clock and the 12.888 timer'
O n e A Z p e r i o d i s : 2 0 0 m s e c .
O V R
I n c a s e o f o v e r r a n g e . w h i c h m e a n s t h a t t h e r e s u l t i s ) 1 0 . 0 0 0 c o u n t e d c l o c k p u l s e s , s i q n a l O V R b e c o m e s a c t i v e
( l o g i c 1 ) .
When a manual range is selected, signal OV R will cause t h e d i s p l a v t o b e s w i t c h e d t o o v e r r a n g e
( d i s p l a v O ) .
D S l , D S 2 , L A E N
D S 1 , D S 2 ( d i g i t s e l e c t ) a n C L A E N ( l a t c h e n a b l e ) a r e u s e d f o r t i m i n g o f t h e d i s p l a y u n i t .
( R e f e r F i g . 2 5 ) '
S i g n a l s D S l a n d D S 2 a r e s € l e c t i n g t h e d i g i t s f o r s e r i a l d i s p l a y '
S i g n a l L A E N i s u s e d f o r l a t c h i n g t h e B C D i n f o r m a t i o n f o r a L X d i s p l a y
LAEN is not used in the PM 2511 E
A O , A 1 , 4 2 , A 3
S i g n a l s A O , A 1 , A 2 , , A 3 a r e t h e d a t a i n f o r m a t i o n f r o m t h e O O 0 0 5 9 '
T h e s i g n a l s a p p e a r i n b i t p a r a l l e l a n d w o r d s e r i a l i n f o r m a t a o n '
T o g e t h e r w i t h t h e c o n t r o l s i g n a l s D S l , D S 2 a n d L A E N , t h e d a t a i s u s e d f o r s e r i a l d i s p l a y '
P O L
T h e s t a t e o f t h e p o l a n t y s i g n a l ( l o g i c 0 = - , r o g 1 = + ) i s d e t e r m i n e d b y t h e s t a t e o f t h e i n c o m i n g d a t a
s i g n a l .
when more up than down puises are counted in the 1st measuring penod this means
+ polarity.
When more dordn than up pulses are counted this nreans - polarity
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The detection is made by the polarity detection circuit inside the OO 0059'
3 . 3 . 5 . D i s p l a y u n i t N 2 ( F i g . 2 5 a n d 5 4 )
3.3.5.1. Genercl
The displav-section consists of four 7-segment LEDs a BCD to 7-segment decoder, a dual 1 of 4 decoder/
d e m u l t i p l e x e r f o r s e r i a l d i s p l a y a n d t h e p o l a r i t y / u n i t i n d i c a t i o n . T h e d i s p l a y s e c t i o n i s b u i l t o n o n e s m a l l
p.c. board N2. The interconnection between the units in the PM 2517 is made by a 2g'pole interconnectron
strip.
Of the strip not all contacts are used in the Pl\4 2517 E.
ln the PlVl 2517 X all contacts of the strip are used.
3.3.5.2. Data 43, 42. Al , A0
T h e d a t a b i t p a r a | | e | - w o r d s e r i a | i s d e r i v e d f r o m t h e d i g i t a I c o n t r o | | c o o 0 0 5 9 a n d i s 5 u p p | i e d t o t h e B c D
to 7-segment decoder.
As a serial displav ts used the data is switched with the speed of clock signal DS 1 The data
is switched in the
f o l l o w i n g o r d e r : t 0 2 , t 0 3 , t o 0 a n d 1 0 1 ( R e f e r t o t h e t i m i n g d i a g r a m F i g 2 5 ) '
The decoded data trom the BCD to 7-segment decoder is supplied to the LED'5 Dependent
to the decoded
signals DS'1 and DS 2 the correct LED's are switched on'
3.3.5.3. Elank display (40 sec. circuit)
V i a t h e b t a n k i n p u t o f t h e H E F 4 5 1 1 l D 7 O 1 l 4 ) , i t i s p o s s i b l e t o b l a n k t h e d a t a i n t h e
d i s p l a v T h e d e c i m a l
p o i n t , p o l a r i t y a n d u n i t i n d i c a t i o n a r e n o t b l a n k e d . B l a n k i n g t h e d i s p l a y i s u s e d i n t h e S T A N D B Y p o s i t i o n o f
t h e P M 2 5 1 7 E .
W h e n p u s h b u t t o n D I S P L A Y i s a c t i v a t e d , s i g n a l B L b e c o m e s l o g i c 1 a n d t h e d i s p l a y i s a l l o w e d t o l i g h t A f t e r
a b o u t 4 0 s e c . d e l a y i s e n e r g i z e d i n t h e c i r c u i t b u i l t - u p o f V 7 0 5 1 7 0 6 , R 7 1 9 / 7 2 0 / 7 2 1 / o n u n i r N l
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